Alphabetical Mineral Reference

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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Acanthite ... see argentite
Accabar ... See Coral
Colors: black
Comments: can be dyed
Achrite ... see Dioptase
Achroite.... see colorless Tourmaline
Actaeonella... fossil sea snail from Austria
Acmite ... aegerine
sodium iron silicate: (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Crystallography: monoclinic, prismatic (not over 1"); frequently massive in other rocks
Colors: black, brown or green on thin edges Luster: glassy
Hardness: 5 to 6
S.G.: 3.2 to 3.4
Cleavage: perfect
Fracture: uneven
Occurrence: common in U.S.

Actinolite ... See also Tremolite, Nephrite
calcium magnesium (iron) silicate: Ca2(Mg,Fe)5Si8O22(OH)2
Crystallography: Monoclinic; bladed crystals, usually elongated; fibrous, columnar aggregates, massive, granular, often twinned
Colors: Pale to dark green, blackish green, black white (when it is free of iron it is Tremolite)
Luster: Vitreous, at times dull glassy
Hardness: 5.5 - 6
Specific gravity: 3 to 3.05 common (3.03-3.07)
Cleavage: two directions good, fibrous, brittle, the compact variety is tough
Refractive index: 1.619-1.644
Birefringence: .022-.026
Fracture: subconchoidal to uneven
Cleavage: perfect prismatic
Pleochroism : Yellow to dark green, transparent to opaque
Occurrence: Contact metamorphic limestones and dolomites; magnesium-rich limestones and ultrabasic rocks; regionally metamorphosed rocks. Small, dark transparent crystals
Crystal or stone size: to 10 cts
Comments: Catseye, easy to cleave, hard to cut, poor jewelry stone, found in nephrite jade. Confused with: Wollastonite which is commonly fluorescent before heating, and dissolves in hydrochloric acid. Scapolite melts more easily and is or becomes on heating, fluorescent in long wave UV. Epidote melts readily to black slag

Adamantine spar ... see
Corundum

Adamite
zinc arsenate: Zn2(AsO4)(OH)
Crystallography: orthorhombic, drusy crust of short prismatic or horizontally elongated crystals
Colors: Colorless, pale green, yellowish green, yellow shades, bluish green, green, rose, violet, color zoning
Luster: Vitreous
Hardness:3.5
Specific gravity: 4.32-4.48
Cleavage: Good in one direction,fracture conchoidal to uneven
Refractive index: 1.708-1.773
Birefringence: .031-.05
Pleochroism: Colorless, blue-green, yellow-green, pale rose, pale purple, pink
Occurrence: Secondary mineral in the oxidized zone of ore deposits
Crystal or stone size: To 3 cts
Comments: Rare (crystal), poor jewelry material, but a collector's item; brilliant fluorescence in light yellow to white when free of iron, green is non fluorescent and can be distinguished from smithsonite by the lack of CO2 bubbles in solution in HCl
Adularia ... See Feldspar

Aegirine ... See Acmite

African Jade ... Massive green Grossular Garnet
Agalmatolite ... See Pyrophyllite, Pinite, Talc
Agate ... See quartz .. Chalcedony .. Banded Quartz

Agatized Wood...See Quartz, Fossilized Wood, Chalcedony
Agmatite ... Found in migmatites, an ultrametamorphic rock
Color: dark with lighter veins
Comments: contains: quartz, feldspar; used as building stone. Found in the Black Forest (Germany)

Alabaster ... See Calcite, Gypsum

Albite ... See Plagioclase Feldspars
Alexandrite ... see Crysoberyl
Allanite ... orthite
(Ca,Ce,La,Na)2(Al,Fe,Be,Mn,Mg)3(SiO4)3(OH)
Crystal: monoclinic, prismatic
Color: black to dark brown
Luster: pitchy or resinous
Hardness: 5.5 - 6
SG: 2.7 - 4.2
Fracture: subconchoidal to uneven
Cleavage: poor
Environment: pegmatites, as a minor mineral in igneous rocks
Comments: fuses quickly (with bubbling) to a dull black magnetic glass; radioactive

Allemontite .. See Arsenic

Almandine ... See Garnet
Colors: purplish red
Hardness: 7.5
SG: 3.9 to 4.2
RI: 1.76 to 1.81
Comments: colored with iron

Almandite ... almandine ... see Garnet
Alunite ... alumstone
hydrous sulfate of aluminum and potassium: KAl3(SO4)2(OH)6
Crystallography: Hexagonal, usually massive crystals are rare
Colors: white, gray, pink
Luster: vitreous to pearly,translucent to transparent Hardness: 3.5 - 4
Specific gravity: 2.6 - 2.9
Fracture: flat conchoidal to uneven, brittle
Cleavage: basal, brittle, conchoidal to uneven
Occurrence: altered orthoclase feldspar rich rocks, massive alunite
Crystal or stone size: massive crystals are rare
Comments: sometimes florescent orange in LW UV; closely resembles limestone and dolomite; a mountain of alunite is in Marysvale Utah

Amazon Jade ..amazonstone.. see Microcline (Feldspar)

Amazonite ... See Feldspar

Amber... See also Succinite

Amblygonite ... Also Montebrasite, Natromontebrasite
LiAl(PO4)(F,OH)
Crystallography: triclinic, pinacoidal Colors: colorless, yellow, white, light gray green, lilac, gray blue
Luster: glassy
Fracture: uneven to subconchoidal
Hardness: 5.5 to 6
Specific gravity: 3 to 3.1
Cleavage: perfect
Comments: most stones come from pegmatite dikes in Brazil, Main and Burma Lithia; fluorescent in LW weak orange

Amethyst ... see Quartz
Amianthus ... see Tremolite, Actinolite
Ammonite ... shell replaced by pyrite

Amphibolite ... see hornblende .. a rock
Analcime .. Also Pollucite, Zeolite group, Analcite
NaAlSi2O6.H2O
Crystallography: cubic, tetragonal trisoctahedron (trapezohedron) transparent to translucent
Colors: colorless, white, greenish, reddish
Luster: glassy
Hardness: 5 to 5.5
Fracture: subconchoidal
Specific gravity: 2.3
Cleavage: traces of cubic
Comments: after heating to the point of melt and then cooling it florescences yellow green
Anatase ... TiO2 ... titanium oxide
crystallography: tetragonal
Colors: blue, light yellow to brown
Luster: adamantine to submetallic
Hardness: 5.5 to 6
S.G.: 3.8 to 3.9
Cleavage: perfect basal
Fracture: subconchoidal
Comments: collector crystal, found in Alpine regions; NC,MA,CO. & France

Andalusite ...See Kyanite, Sillimanite.^M
Varieties: Chiastolite, Viridine
Al2SiO5
Crystallography: orthorhombic
Colors: green, greenish brown w/ reddish tints chiastolite is impure variety showing gray cross on black or gray ground.
Hardness: 7.5
Specific gravity: 3.15
Cleavage: perfect
Refractive index: mean 1.64 v .01
Pleochroism: striking in one direction
Comments: often confused with tourmaline, but has lower DR & higher SG

Andesite ... igneous rock
Essentials: plagioclase, anorthite, biotite
Accessories: magnetite, ilmenite, quartz, hornblende pyroxene, glass
Accidentals: olivine, orthoclase, anorthoclase
Andradine ...see garnet .. andradite
Crystallography: Isometric
Colors : Demantoid is green, Topazolite is yellow, Leuco is colorless Hardness: 6.5
Specific gravity: 3.85
Refractive index: 1.89
Comments: very high dispersion not usually suitable for jewelry, varieties as demantoid, melanite and topazolite usually have gem qualities.

Anglesite ... lead sulfate ... PbSO4
Crystal system: Orthorhombic
Colors: colorless to white, gray, green, brown, black.
Hardness: 2.75 to 3 very soft
Specific gravity: 6.3
Comments: alteration of galena in oxidation areas of lead deposits. Faceted stones from Morocco (colorless 19 ct.) were sold for $50.00 per.ct. (1994)

Anhydrite ... CaSO4
Crystallography: orthorhombic
Colors: colorless, bluish, red - violet Hardness: 3.5
Specific gravity: 2.9 - 2.99
Cleavage: 3 good
Fracture: uneven to splintery
Environment: sedimentary beds, gangue in ore veins and in traprock zeolite occurrences. Crystals are collector items. Sometimes fluorescent. Easily altered to gypsum through hydration.
Annabergite ... hydrated nickel arsenate
(Ni,Co)3(AsO4)2.8H2O
Crystal system: monoclinic
Color: white to green
Luster: silky to glassy
SG: 3.1
Hardness: 2.5 - 3.0
Comments: forms as crust on nickel minerals, sometimes replacing the mineral completely; Best place to see in the US is in Humboldt, CO.

Anorthite ... a variety of feldspar ...see labradorite, oligoclase
sodium calcium alum. silicate
Color: colorless, white, yellowish, green, pink, to reddish
SG: 2.62 - 2.76
Comments: can be found in triclinic crystals or in massive form

Anorthosite ... intrusive igneous rock
Color: dark gray
Comments: contains plagioclase, anorthite, labradorite - bytownite, orthopyroxene, with some olivine, magnetite, ilmenite, apatite, chromite, and sulfide. It also rarely contains biotite, hornblende and cordierite. Can be found in San Diego,CA.
Anthophyllite ...(Mg,Fe)7Si8O22(OH)2... hydrous magnesium iron silicate
Crystal sys.: orthorhombic
Color: gray, light green, light brown
SG: 2.8 - 3.2
Hardness: 5.5 - 6
Cleavage: prismatic
Comments: modification of olivine through hydration crystals are rare. Franklin Co. N.C.
Anthracite ... bituminous coal ... jet Crystallography: organic
Colors: black
Luster: high
Hardness: 2.5 - 4
Specific gravity: 1.3 - 1.35
Cleavage: none
Refractive index: 1.64 - 1.68
Pleochroism: none
Crystal or stone size: massive
Occurrence: world wide: Spain, France, U.S. Comments: when rubbed can become electrically charged.

Antigorite ... see serpentine

Antimony ... see arsenic

Antlerite...Cu3(SO4)(OH)4...Sulfate of copper
Crystal: Rhombic bipyramidal
Color: bright to dark green
Luster: glassy
Hardness: 3.5 - 4
SG: 3.9
Fracture: uneven
Cleavage: pinacoidal perfect side, poor front
Comments: Like brochantite is a mineral of the oxidized zones of copper deposits in siliceous rocks that cannot supply an abundance of the CO2 required for the formation of the carbonate group of copper minerals.

Apache Tears ... see obsidian
Comments: round or simi round, marble like, dark blackish green.

Apatite Crystallography: hexagonal
Colors: yellow, blue, green, violet
Hardness: 5
Specific gravity: 3.18 to 3.21
Cleavage: none
Refractive index: avg. 1.638 v .003
Occurrence: blue from Burma, strong dichroism Comments: yellow shows rare earth absorption bands (584 nm.); very low DR & higher SG distinguish it from danburite
Aplite ... see orthoclase

Apophyllite Crystallography: tetragonal
Colors: pink
Hardness: 4.5 to 5
Specific gravity: 2.3 to 2.5
Refractive index: avg. 1.536 v. .001
Comments: hydrated potassium-calcium fluosilicate rarely cut, a collector gem.
Aquamarine ... see Beryl Refractive index: 1.75 +/- .006

Aragonite Crystallography: orthorhombic
Colors: colorless various tints
Luster: vitreous
Hardness: 3.5 - 4
Specific gravity: 2.94
Refractive index: 1.53 - 1.685
Occurrence: can form crystals large enough to cut Comments: is the "orient" produced by overlapping of platelets near a pearls surface (pearl RI is 1.52 - 1.69).

Arenite ... clastic sedimentary rock
Color: variable, from white to gray, yellow, green, red to brown.
Comments: composed of quartz sand with other minerals as color: feldspar, mica, calcite, zircon, apatite, olivine, monazite, pyrite, magnetite, gypsum, glauconite.
Arfvedsonite ... hydrous sodium iron mag. alum. silicate
Crystal Sys.: monoclinic
Color: black to greenish black
SG: 3.5
Hardness: 5
Comments: found in alkaline plutocic rocks rich in iron and in rare metamorphic schist.
Argentite ... acanthite
Crystallography: cubic
Colors: black, gray
Luster: metallic
Hardness: 2 to 2.5
Specific gravity: 7.3
Cleavage: poor
Fracture: subconchoidal
Comments:
Argillite ... sedimentary rock
Color: light to dark gray to black
Comments: fine grain, mixture of clay minerals with quartz, feldspar, mica, some carbon, iron oxides, gypsum, & pyrite. Classic marine & glacial deposits.

Arkansas diamond ... see clear quartz Comments: so named because some of the best come from Arkansas

Arkose ... sedimentary rock
Color: gray, pink or reddish
Comments: coarse grains of feldspar, some quartz, biotite, mica and other minerals derived from igneous and lithic fragments, the binding agent may be silicate, calcitic, or limonitic.

Arsenoferrite ... see skutterudite

Arsenic ...
Crystal system: hexagonal (rare)
Color: black w/ white incrustations
SG: 5.4 - 5.9
Hardness: 3.5
Comments: hydrothermal veins; associated with silver, nickel, cobalt.

Arsenopyrite ... iron arsenic sulfide
Color: silver to whitish gray with pink tints SG: 5.9 - 6.2
Hardness: 5.5 - 6

Asbestos .. see tremolite , actinolite , serpentine
Comments: asbestos is a finely fibrous serpentine; crysotile is a coarser fibrous type.
Artinite ... hydrated magnesium carbonate Crystal system: monoclinic
Color: white to gray
SG: 2.03
Hardness: 2

Astrophyllite ... hydrous potassium iron titanium silicate
Color: golden yellow to yellow brown
SG: 3.3 - 3.4
Hardness: 3.5 - 4.5

Atacamite ... hydrous copper chloride
Crystal sys. orthorhombic
Color: green
SG: 3.76
Hardness: 3 - 3.5

Augelite ... Colors: colorless to brownish
Hardness: 4
Specific gravity: 2.7
Refractive index: 1.574 to 1.588
Comments: aluminum phosphate

Augite ... calcium magnesium iron aluminum silicate..(see pyroxene)
Aurichalcite ... hydrous zinc copper carbonate Color: light blue
SG: 4.2
Hardness: 2 - 2.5

Austinite .. Australite .. moldavite from Australia Colors: bottle green to brown green
Hardness: 5.5
Specific gravity: 2.32 - 2.38
Cleavage: none
Refractive index: 1.48 - 1.5
Comments: tektite formed from rock which has melted after being hit by a meteorite
Autunite ... hydrated copper uranium phosphate Crystal sys. tetragonal
Color: greenish yellow
SG: 3.2
Hardness: 2 - 2.5

Aventurine .. see quartz
Axinite Crystallography: triclinic
Colors: blue, clove brown, violet
Fracture: conchoidal, brittle
Hardness: 7
Specific gravity : avg. 3.28
Cleavage: perfect
Refractive index: 1.685 + - .011
Pleochroism: strong; olive green, red - brown, yellow - brown
Occurrence: in bladed crystals,U.S.,France,Mexico Comments: occurs in bladed crystals

Azurite
Babingtonite ... Hydrous calcium iron manganese silicate
Crystal sys: triclinic
Color: black or blue to brown when altered
SG: 3.4
Hardness: 5.5 - 6

Bakerite ... see howlite

Balas
ruby ... see spinel

Banded agate...see quartz..chalcedony
Barite ...
Crystallography: orthorhombic
Colors: colorless, yellow, red, green, black
Hardness: 2.5 - 3.5
Specific gravity: 4.48
Occurrence: med. to low temp. hydrothermal veins assoc. with lead, silver, antimony Also deposits in hot springs Crystal or stone size: up to 3.3 ft.
Comments: sometimes fluorescent

Basalt ... A basic igneous rock
Basalt is formed from a lava that solidifies to a fine grained black rock composed of microscopic grains of calcium sodium (plagioclase) feldspar, pyroxene, and olivine, but with no quartz.
Basanite ... see quartz .. also touchstone
Colors: velvet black

Bastite ... bastinite ... hureaulite
Hydrous manganese phosphate
Crystal sys: monoclinic
Color: pink, gray, yellow, reddish brown SG: 3.2
Hardness: 3.5
Comments: pronounced {hoo-ray'o-lite}

Bauxite ... {bawks'-yt}
Crystallography: none, an aggregate
Colors: reddish to brown, white to yellowish Luster: vitreous to pearly
Hardness: 2.5 - 3
Specific gravity: 2.3 - 2.7
Cleavage: perfect
Occurrence: sedimentary ; Surinam, Jamaica, US, world wide.
Comments
Becquerelite ... see gemmite

Benitoite
Crystallography: Hexagonal
Colors: sapphire blue to colorless
Hardness: 6.5
Specific gravity: 3.67
Refractive index: 1.78 + - .047
Comments: Rare stone from San Benito Co. Cal. strong DR and high dispersion
Bertrandite
Crystallography: orthorhombic
Colors: colorless to pale yellow
Luster: vitreous
Hardness: 6 -7
Specific gravity: 2.6
Cleavage: excellent prismatic
Occurrence : pegmatites US
Crystal or stone size: to 1 cm
Comments: of interest to mineralogists & collectors
Beryl {bair'-ul}...see also aquamarine , emerald, heliodor, morganite
Colors: colorless, gold, yellow-green, yellow, pink, , green (emerald), pale blue to blue green (Aquamarine), golden to yellow (heliodor), pink (Morganite)
Beryllonite ... NaBePO4 ... sodium beryllium phosphate
Crystal: monoclinic
Hardness: 5.5 - 6
Luster: glassy
SG: 2.8
Fracture: conchoidal
Cleavage: good basal, brittle, transparent to translucent
Comments: Fuses with difficulty to a cloudy glass, wet with sulfuric acid and the powdered mineral froths. coloring flame is yellow.

Betafite ... hydrous uranium titanium niobium oxide
Crystal sys: isometric
Color: black, sometimes coated w/greenish brown or yellow surface alteration
SG: 3.7 - 5
Hardness: 5
Comments: occurs in pegmatites, ore of uranium thorium, niobium.

Bindheimite ... see boulangerite

Binnite ... see tetrahedrite tennantite
Biotite ... see mica
Bismuth ... {biz'-muhth}
Crystal sys: hexagonal
Color: A tarnished rose pink
SG: 9.7 - 9.8
Hardness: 2 - 2.5
Comments
Bismuthinite ... bismutite
Crystal sys: orthorhombic
Color: gray
SG: 6.4 - 6.5
Hardness: 2
Comments: rare free growing needles, first named cannizarite because of unbismuthlike needles. Found in NY,CO,Brazil
Bixbite ... collector mineral (bixbyite) Crystal system: cubic
Color: Black, metallic
H: 6 - 6.5
SG: 4.9 - 5.1
Brittle

Blend ... sphalrite Crystallography: cubic
Colors: brown, yellow, orange, black, transparent to opaque green
Hardness: 3.5
Specific gravity: 3.09
Cleavage: perfect dodecahedral
Refractive index: avg. 2.37
Comments: good color luster and fire but too soft to take a high polish

Bloodstone...see chalcedony (quartz) Colors : usually green with red spots
Luster: dull to waxy
Hardness: 7 or less
Specific gravity: 2.55 to 2.62
Cleavage: none
Refractive index: 1.535 to 1.539

Boehmite ... see bauxite

Boleite ... hydrated lead copper chloride Crystal sys: tetragonal
Color: dark blue
SG: 5.05
Hardness: 3.5

Bonamite ... see smithsonite H: 5
SG: 4.35
RI: 1.62

Borax {bohr'-ahn} boron, hydrated sodium borate, borax acid
Crystal sys: monoclinic
Color:colorless to white with yellow or blue tint
SG: 1.74
Hardness: 2 - 2.5
Comments
Bornite ... {bohr'-nyt}...copper iron sulfide Crystallography: isometric
Colors: reddish brown, showing purple tarnish
Hardness: 3
Specific gravity: 5 - 5.7
Comments
Boulangerite ... lead antimony sulfide Crystallography: orthorhombic
Colors: dark gray to black
Luster: metallic
Hardness: 2.5 - 3
Specific gravity: 5.7 - 5.9
Occurrence: hydrothermal veins, found with galena,silver, antimony deposits. Crystal or stone size: stubby or tubular prismatic crystals. Comments: dissolves in nitric acid

Bort ... see diamond ... bortz Comments: diamond unsuitable for gemstones, used in cutting and polishing.

Bournonite ... lead copper antimony sulfide
Crystallography: orthorhombic
Colors: dark gray to black
Luster: metallic
Hardness:2.5 - 3
Specific gravity: 5.7 - 5.9
Cleavage: good
Comments: used as an ore of lead and copper
Bowenite SG:2.59
Avg.RI: 1.55
H: 5.5

Brazilianite Crystallography: monoclinic
Colors: colorless to greenish yellow to transparent or translucent
Hardness: 5.5
Specific gravity: 2.99
Refractive index: avg. 1.612 v. .021
Occurrence : Minas Gerais, & New Hampshire
Breccia ... {brech'-ee-uh} sedimentary rock
Crystallography : none
Colors : variable
Luster : can be polished like marble
Hardness: variable
Occurrence: found in limestone and dolomite Crystal or stone size: massive
Comments
Breithauptite ... see niccolite

Brochantite ... hydrous copper sulfate
Crystallography: monoclinic
Colors : bright green
Hardness: 3.5- 4
Specific gravity: 3.97
Cleavage: perfect
Comments: ore of copper

Bromyrite ... bromargyrite
Crystal system: cubic
Colors: colorless, greenish gray, gray to violet brown
Adamantine luster
H: 1 - 1.5
SG: 5.5

Bronzite ... see enstatite ... hypersthene
Crystallography: orthorhombic
Colors : greenish brown or blackish
Luster: submetallic
Hardness: 5
Specific gravity: 3.2 - 3.5

Brookite ... titanium oxide
Crystallography: orthorhombic
Colors: brown to black sometimes banded
Luster: adamantine
Hardness: 5.5 - 6
Specific gravity: 4.1
Cleavage: imperfect
Comments: ore of titanium

Brownspar ... see calcite

Brucite ... magnesium hydroxide
Crystallography: hexagonal
Colors: colorless, green, blue, pinkish yellow, brown
Luster: pearly
Hardness: 2.5
Specific gravity: 2.4
Occurrence: fracture planes in serpentinized peridotites in asbestos mines
Comments: used for magnesia refractories and a source of metallic magnesium.
Buergerite ... see tourmaline

Bytownite ... see plagioclase feldspar
Cabrerite ... see annabergite

Calamine ... hemimorphite ... smithsonite
hydrated zinc silicate ... ore of zinc
Calaverite ... AuTe2 ... see sylvanite (Au,Ag)Te2
Calciphyre ... calci - silicate rocks
Color: yellow brown w/pink/light green/white & dark red zones
Comments
Calcite ... calcium carbonate
Crystallography: hexagonal
Colors: whitish, red, pink, yellow, blue
Luster: iridescent or pearly
Hardness: 3
Specific gravity: 2.71
Comments: some are fluorescent in UV, red, yellow pink blue

Caledonite ... Cu2Pb5(SO4)3(CO3)(OH)6... carbonate sulfate of lead and copper
Color: light blue to light blue green
Crystal: orthorhombic
Luster: resinous
Hardness: 2.5 - 3
SG: 5.8
Fracture: uneven
Cleavage: 1 good, 1 poor, brittle, translucent
Comments: rare

Californite ... see vesuvianite... hydrous calcium magnesium aluminum silicate. an aggregate combo of idocrase and grossular garnet
Color: apple green
SG: 3.3
Avg.RI: 1.7
H: 5.5 to 7.5
Comments: $450.00 per ct. when cut from crystal.
Calomel ... HgCl ...
Crystal: tetragonal, (minute)
Color: gray to yellowish
Luster: adamantine
Hardness: 1 - 2
SG: 6.5
Fracture: conchoidal
Cleavage: 2 , 1 good, sectile, translucent Comments: Fluorescent red

Campylite ... see mimetite

Cancrinite ... tectosilicate
Crystallography: hexagonal
Colors: colorless, yellow, white, reddish, violet
Hardness: 5 - 6
Specific gravity: 2.4 - 2.5
Comments: collector item

Cannizarite ... see bismuthinite

Carbonatite ... igneous rock
Color: gray to yellowish
Comments: South Africa; used in the extraction of minerals and rare elements

Carnallite ... hydrated potassium magnesium chloride
Crystal sys: orthorhombic
Color: colorless to reddish pink
SG: 1.6
Hardness: 2.5
Comments: potassium fertilizer

Carnelian ... see chalcedony
Colors: red to orange
Occurrence: looks like jade and fire opal
Carnotite ... hydrated potassium uranium vanadate
Crystallography: monoclinic
Colors: canary yellow
Hardness: very soft, clumpy powder
Specific gravity: 4.7 - 5
Cleavage: perfect
Occurrence: very common in desert areas of U.S.
Crystal or stone size: crystals are rare
Comments: ore of uranium and vanadium
Cassiterite ... tin oxide
Crystallography: tetragonal
Colors : colorless to dark brown
Luster: adamantine
Hardness: 6.5
Specific gravity: 6.95 to 7
Cleavage: imperfect conchoidal
Refractive index: avg. 2.045 v. .096
Comments: high luster and dispersion, has been used as a diamond substitute
Celestite ... celestine ... strontium sulfate
Colors: colorless, white, red brown, orange, light blue.
Luster: glassy
H: 3 - 3.5
SG:3.9 - 4
Comments: sometimes fluorescent, geodes from Madagascar can be lined with these blue crystals.

Cerargyrite .. bromyrite .. secondary silver ore
Color: greenish gray to gray
H: 1 - 1.5
SG: 5.5
Comments: composed of 60 to 75 % silver chloride yellow crystals were found in New South Wales, which darken to gray in sunlight.
Cerussite ... lead carbonate
Crystallography: orthorhombic
Colors: colorless, white
Luster: Adamantine
Hardness: 3 - 3.5
Specific gravity: 6.5
Occurrence: Namibia, new Mexico, Rhodesia USSR, Germany, Colorado
Crystal or stone size: some crystals are very large, 50/60 cts, @ $100 per ct.
Comments: ore for lead, bright green fluorescence
Cervantite ... stibnite .. antimony sulfide
Crystal sys: orthorhombic
Color: red (kermesite), yellow
SG: 4.6 -4.7
Hardness: 2
Comments: ore of antimony

Chabazite ... hydrated calcium aluminum silicate
Crystallography: hexagonal
Colors: colorless, white, greenish, reddish
Luster: vitreous
Hardness: 4 - 5
Specific gravity: 2.05
Cleavage: good rhombohedral
Occurrence: world wide, intrusive igneous rocks Comments: collector item

Chalcanthite ... hydrated copper sulfate
ore of copper
Crystal sys: triclinic
Color: colorless
SG: 2.3
Hardness: 2.5
Comments: major ore of copper in Chile
Chalcedony
types
Crystallography: fine grained quartz
Colors: all
Luster: waxy
Hardness: 6.5 - 7
Specific gravity: 2.6 + - .05
Cleavage: none
Refractive index: 1.535 - 1.539
Crystal or stone size: can be massive
Comments: this is a very general name for all fine grained quartz.look up types under its own name

Chalcocite ... tobernite ... copper sulfide
Crystal sys; orthorhombic
Color: dull gray, surface altered to black/green
SG: 5.5 - 5.8
Hardness: 2.5 - 3
Comments: ore of copper

Chalcopyrite {kal-koh-py'-rite} copper iron sulfide
Crystallography: tetragonal
Colors: brassy yellow
Luster: metallic
Hardness: 3.5 - 4
Specific gravity: 4.2 - 4.3
Cleavage: none
Occurrence: world wide
Crystal or stone size: massive
Comments
Chalcosine ... see chalcocite

Chalcotrickite ... cuprite ... copper oxide
Crystallography: isometric
Colors: ruby red
Luster: adamantine
Hardness: 3.5 - 4
Specific gravity: 5.8 - 6.2
Crystal or stone size: rare crystals have been cut as gems
Comments: ore of copper

Chert ... see quartz

Chessylite ... see azurite

Chiastolite ... see andalusite

Childrenite ...(Fe,Mn)Al(PO4)(OH)2.H2O... Hydrous iron and manganese aluminum phosphate
Crystal: orthorhmbic
Color: pink to light brown, gray to black
Luster: glassy
Hardness: 4.5
SG: 3.06 - 3.25
Fracture: conchoidal
Cleavage: front and side pinacoid, brittle
Chlorargyrite ... silver chloride
Crystal sys: isometric
Color: gray, tarnish to greenish/purple/brown
SG: 5.5 - 5.6
Hardness: 1 - 1.5
Comments: silver ore, hard to find

Chloritoid ... hydrous iron magnesium aluminum silicate
Crystallography: monoclinic and triclinic
Colors: yellow - green to black
Luster: vitreous to pearly
Hardness: 6.5
Specific gravity: 3.51 - 3.8
Occurrence: found in low grade metamorphic rocks rich in aluminum, iron and manganese
Crystal or stone size: in contact with marbles corundum and quartz.
Comments: collector item

Chondrodite
Crystal system: monoclinic
Colors: yellow to dark reddish brown
Luster: resinous
Hardness: 6 - 6.5
SG: 3.14
Cleavage: poor
Comments: fine crystals are found in Sweden a collector item.
Chromite ... iron chromium oxide
Crystallography: isometric
Colors: black
Luster: submetallic
Hardness: 5.5
Specific gravity: 4.5 - 4.8
Cleavage: none
Crystal or stone size: massive
Comments: ore of chromium, a chromium and iron oxide, in the SPINEL group of minerals. Metallic black chromite generally is associated with serpentinites, peridotites, and related rocks. It forms large, irregular, compact masses in ore deposits and also occurs in stony iron meteorites.

Chrysoberyl...{kris'-uh-bair-ul}... cymophane, alexandrite, cats eye
Crystallography: orthorhombic
Colors: green/red (alexandrite), greenish or brownish yellow to translucent and chatoyant (cat eye) colorless to brown
Hardness: 8.5
Specific gravity: 3.71 - 3.73
Cleavage: distinct in two directions
Refractive index: avg. 1.75 v. .009
Pleochroism: strong in alexandrite
Occurrence: Siberia, Brazil
Crystal or stone size: Alexandrite in Siberia less than 1 ct. Brazilian stones are larger.
Comments
Crysocolla ... see chalcedony SG: 2.1
Avg. RI: 1.5
H: 2

Chrysolite ... see olivine

Chrysotile ... see serpentine ... asbestos
Chrysoprase...see chalcedony
Color : yellowish green
SG: 2.6
Avg.RI: 1.53
H: 7
Comments: confused with jade, poor emerald, serpentine

Cinnabar {sin'-uh-bar} cinnabarite, mercury sulfide
Crystallography: hexagonal
Colors: red, pink
Hardness: 2 - 2.5
Specific gravity: 8.1
Cleavage: perfect
low temp. hydrothermal deposits
Comments
Citrine ... see quartz
Clinochlore...see chlorite...hydrous magnesium iron - aluminium silicate... see penninite
Crystallography: monoclinic
Colors: blue green, yellow, rare white
Luster: pearly
Hardness: 2 - 2.5
Specific gravity: 2.6 - 2.8
Cleavage: perfect basal
Comments: of interest to collectors

Clinoenstatite...see enstatite, hypersthene
Clinozoisite...Hydrous calcium aluminum silicate
Crystal sys: monoclinic
Color: gray, pale green, pink
SG: 3.3 - 3.5
Hardness: 6.5
Comments: Elongated prismatic crystals, poorly terminated

Cobaltite ... cobalt arsenic sulfate
Crystallography: orthorhombic
Colors: gray, violet to purple tint
Luster: metallic
Hardness: 5.5
Specific gravity: 6.3
Cleavage: perfect
Crystal or stone size: 1"
Comments: CoAsS, is the chief ore mineral of cobalt, containing up to 35 percent of the element. A secondary source of arsenic, cobaltite contains up to 10 percent iron and some nickel as impurities. The cubic crystals (ISOMETRIC SYSTEM) are silver white. Luster metallic, streak grayish black. It occurs with other cobalt and nickel minerals and, more commonly, in contact metamorphic zones.

Colemanite ... hydrated calcium borate
Color: white, tinted red to pink by impurities
SG: 2.4
Hardness: 4 - 4.5
Comments: A main ore of boron

Columbite - tantalite group,iron maganese niobium tantalum oxide
Crystal System: orthorhombic
Colors: black
SG: 5.3 - 8.1
Comments: Ore of niobium and tantalum, used in stainless steel

Conichalcite... hydrous calcium copper arsenate
Crystal sys: Orthorhombic
Color: shades of green
SG: 4.3
Hardness: 4.5
Comments: A secondary mineral occurring in the oxidation of copper

Copiapite ... hydrated iron sulfate
Crystal sys: triclinic
Color: olive green to yellow or orange
SG: 2.08 - 2.17
Hardness: 2.5
Comments: A secondary mineral that occurs in the upper portions of sulfide deposits, dissolves easily in water.

Copper
Crystal sys: isometric
Color: copper color tinted with green or blackish film
SG: 8.93
Hardness: 2.5 - 3
Comments
Coral ... White, pink, black, red
Crystallography: none, organic
Colors: red, pink, black, white, can be dyed
Hardness: 3.5 - 4
Specific gravity: 2.12
Refractive index: 1.55 - 1.57
Occurrence: warm seas
Comments: Coral has a tree-like form, and a radial fibrous cross section. White is the most common, coral occurs in warm tropical waters having a temp. above 68 F. The Romans believed it had strong healing powers.
Cordierite...{kohr'-dee-uh-ryt}... magnesium aluminum silicate...iolite
Crystallography: orthorhombic
Colors: gray, blue, black, purple
Luster: glassy
Hardness: 7 - 7.5
Specific gravity: 2.61 - 2.66
Cleavage: poor, gem v. distinct
Refractive index: 1.542 - 1.551
Comments
Corundum{kuh-ruhm'-duhm}...sapphire...ruby
Crystallography: Hexagonal
Colors: red = ruby, all other colors = sapphire red - orange = padparadsha sapphire
Hardness: 9
Specific gravity: 3.99
Cleavage: false ,which may be well developed
Refractive index: avg. 1.762 to 1.77 v. .008
Comments
Covellite ... covelline ... copper sulfide
Crystal sys: hexagonal
Color: indigo blue
SG: 4.59 - 4.76
Hardness: 1.5 - 2
Comments: ore of copper

Cristobalite ... silicon oxide
Color: colorless to white or gray
SG: 2.3
Hardness: 7
Comments: only of interest to collectors
Crocidolite SG: 2.66
Avg.RI: 1.54
H: 7

Cryolite ... sodium aluminum fluoride
Crystallography: monoclinic
Colors: white , colorless
Luster: vitreous or pearly
Hardness: 2.5
Specific gravity: 2.95 - 3
Comments: used in pottery glazes and glass
Cubic Zirconia...man made
Colors: all
Hardness: 8.5
Specific gravity: 5.8 + - .2
Refractive index: 2.15 + - .03
Occurrence: man made
Crystal or stone size: up to 2" usual 1" or less
Comments: usually orange or yellow fluor. under UV.

Cummingtonite...hydrous magnesium silicate
Crystal sys: monoclinic
Color: brown
SG: 3.1 - 3.7
Hardness: 5 - 6
Comments: of interest to collectors

Cuprite...{koop'-ryt}... copper oxide
Crystallography: isometric
Colors: dark ruby red
Luster:adamantine
Hardness: 3.5 - 4
Specific gravity: 5.8 - 6.2
Comments: Cuprite, copper oxide is a common and widespread ore mineral formed by oxidation of sulfide minerals in the upper zones of copper veins. It forms octahedral crystals (ISOMETRIC SYSTEM) and granular masses that are various shades of red; parallel, elongated ruby -red needles are called chalcotrichite, and brick - red earthy masses are called tile ore. Cuprite's streak is bright brownish red. Some crystals are cut as gems @ $200.00 per ct.

Cyanite...see kyanite Color: blue
SG: 3.67
Hardness: 6-7 one direction/4-5 in the other Comments: sometimes used as gemstone, also used in the manufacture of porcelain.
Cyanotrichite ... hydrated copper aluminum sulfate
Color: blue
SG: 2.75
Hardness: 1
Comments: rare alteration in copper deposits.
Dacite ... extrusive igneous rock
Colors: medium gray
Occurrence: lava flows, dikes
Crystal or stone size: massive
Comments: no commercial value

Danburite ... calcium borosilicate
Crystallography: orthorhombic
Colors: pale yellow, colorless
Luster: vitreous
Hardness: 7
Specific gravity: 3
Cleavage: poor
Refractive index: avg. 1.633 v. .006
Occurrence: Burma
Crystal or stone size:
Comments: Lower SG / RI distinguish it from topaz.

Datolite...hydrous calcium borosilicate
Crystallography: monoclinic
Colors: colorless to yellow to brown, cloudy nodules in various colors.
Luster: vitreous
Hardness: 5
Specific gravity: 2.99
Refractive index: avg. 1.648 v. .044
Crystal or stone size: to 5 cts. cab.cut @ 250 pc.
Comments: collector stone, ore of boron
Demantoid....
garnet...andradite
Crystallography:
Colors: green
Hardness: 6.5 - 7
Specific gravity: 3.85
Refractive index: 1.875 -1.89
Comments: high dispersion, horse tail inclusions
Dendrite ... pyrolusite ...maganese oxide
Crystallography: tetragonal
Colors : black
Luster: submetallic
Hardness: 6 - 6.5
Specific gravity: 4.7 - 5
Comments: can be tree like inclusions
Descloizite ... hydrous lead zinc vanadate
Crystallography: orthorhombic
Colors: orange to reddish brown
Luster: greasy
Hardness: 3.5
Specific gravity: 5.5 - 6.2
Occurrence: massive
Comments: rare ore of vanadium

Diabase ... {dy'-uh-bays} igneous rock Comments
Diamond...(boart, carbonado are industrial types)
Occurrence
Comments
Diaspore ... see bauxite

Diopside... pyroxene group
Crystallography: monoclinic
Colors : pale to dark green
Hardness: 5
Specific gravity: 3.29
Refractive index: avg. 1.69 v. .03
Chatoyant: some 4 ray stars
Comments : Different shade of green from peridot and higher RI lower DR. Enstatite has lower DR

Dioptase ... hydrous copper silicate
Crystallography: hexagonal
Colors: green
Hardness: 5
Specific gravity: 3.3
Cleavage: perfect
Comments: used as cabs in jewelry, rare faceted blue green stones up to 2 cts. @ 500 a piece
Diorite {dy'-uh-ryt} intrusive igneous rock
Colors: dark gray
Comments
Dolomite {doh'-luh-myt} calcium magnesium carbonate
Crystallography: hexagonal
Colors: colorless, white, pink, yellowish Luster: vitreous
Hardness: 3.5 - 4
Specific gravity: 2.85 - 2.95
Comments
Dumortierite ... aluminum borosilicate
Crystallography: orthorhombic
Colors: blue, violet reddish brown
Luster: vitreous
Hardness: 7
Specific gravity: 3.45
Occurrence: world wide
Comments: used in manufacture of aluminums refractories

Dunite {doo'-nyt} intrusive igneous rock...see olivine
Colors: light green
Comments
Eclogite {ek'-luh-jite}... metamorphic rock
Color: white with red
Comments
Ekanite Colors: green
Luster: glassy
Hardness: 5 - 6.5
Specific gravity: 3.28
Refractive index: 1.597
Occurrence: Ceylon
Crystal or stone size: 1 to 3 cts.
Comments: radioactive, collector gem, @ 150 per ct.
Embrechite ... Migmatite .. ultrametamorphic rock
Color: white w/black
Comments: essentials: quartz, potassic feldspar oligoclase, biotite sometimes: zircon apatite, magnetite. Rare: muscovite, cordierite, sillimanite, garnet
Embolite ... see cerargyrite .. bromyrite

Emerald...see beryl
Crystal or stone size: usually less than 2 ct. in gem quality.
Comments
Enargite {en-ar'-jite}.. copper arsenic sulfide
Crystal sys: orthorhombic
Color:gray to black
SG: 4.4 - 4.5
Hardness: 3
Comments: Enargite, a fairly rare copper arsenic sulfide mineral, is an important ore of copper and arsenic in the few places where it is abundant, such as Bor, Yugoslavia and Butte, Mont. Enargite forms metallic black, tabular, or prismatic crystals and granular, cleavable masses in vein and replacement deposits of intermediate temperature. Streak is grayish black.

Enstatite
Crystallography: Rhombic
Colors : green, brown, colorless
Hardness: 5.5 - 6
Specific gravity: 3.25
Refractive index: 1.658 - 1.668
Birefringence: .01
Occurrence: south Africa, Burma
Comments:some chatoyant.Absorption line @ 506 nm $100 per ct. for faceted transparent stones

Eosphorite ... childrenite .. hydrated manganese aluminum phosphate
Crystal sys: monoclinic
Color:pink to brown
SG: 3.1 - 3.2
Hardness: 5
Comments: occurs in granite pegmatites with apatite, manganese phosphates and rose quartz

Epidote...{ep'-i-doht}
Crystallography: monoclinic
Colors: dark brownish green,yellowish, red, yellow, gray
Hardness:6.5
Specific gravity: 3.25 - 3.45
Cleavage: excellent
Refractive index: avg. 1.75 v. .035
Birefringence: .019 - .045
Pleochroism: strong green, dark brown, yellow
Comments: Color of crystals usually too dark to make good gemstones. strong dichroic. distinctive pistachio green. Epidote is the principal member of a group of silicate minerals that occur most commonly in low grade, calcareous metamorphic rocks and also in igneous rocks, where they have altered from feldspar, pyroxene, and amphibole minerals. A calcium aluminosilicate, epidote forms pistachio green to dark green elongated crystals, disseminated grains, or fibrous or granular masses that have perfect cleavage in one direction. Luster vitreous.
Epsomite ... hydrous magnesium sulfate
Crystal sys: orthorhombic
Color: colorless to white
SG: 1.67
Hardness: 2 - 2.5
Comments: epsom salts

Erythrite ... hydrated cobalt arsenate
Crystallography: monoclinic
Colors: red to gray
Luster: vitreous to pearly
Hardness: 1.5 - 2.5
Specific gravity: 3.07
Cleavage: perfect

Essonite ... see garnet ... hessonite

Euclase
Crystallography: monoclinic
Colors: pale green or blue some yellow, colorless
Luster: vitreous
Hardness: 7.5
Specific gravity: 3.1
Cleavage : very good
Refractive index: avg. 1.665 v. .019
Crystal or stone size:
Comments: appearance & RI almost identical to fibrolite, distinguish by lower SG.
Fauslite... see turquoise
Comments: turquoise which zinc is the colorent
Feldspar
Types: orthoclase, microcline moonstone, labradorite, amazonite, albite, plagioclases, cat's eye, sunstone

Ferberite ... heubnerite .. iron maganese tungstate
Crystallography: monoclinic
Colors: reddish brown, blackish brown, black
Hardness: 5 - 5.5
Specific gravity: 7.1 - 7.5
Comments: main ore of tungsten

Fergusonite (sp) ... see monazite

Ferroaxinite ... manganaxinite .. hydrous calcium iron manganese borosilicate
Color: reddish brown to yellow, violet and gray sometimes green when incrusted with clorite
SG: 3.25
Hardness: 6.5 - 7
Comments: a rare and unusual gemstone

Ferruginous quartz ... Monazite .. rare earth phosphate
Crystallography: monoclinic
Colors: yellow to brownish red
Luster: vitreous to waxy
Hardness: 5 - 5.5
Specific gravity: 4.8 - 5.5
Comments: ore of cerium and thorium

Fibrolite
Colors: pale blue, greenish
Hardness:7.5
Specific gravity: 3.25
Cleavage : very good
Refractive index: avg. 1.665 v. .019
Crystal or stone size:
Comments: same RI as Euclase

Flint...see quartz, chert, chalcedony, siliceous rock
Color: white, gray, red, black, some zoned
Comments
Flosferri ... see aragonite

Fluorite {flohr'-yt} fluor spar, blue John, Derbyshire spar
Crystallography: isometric
Colors : Purple, blue, green, yellow, pink, colorless
Luster: vitreous
Hardness: 4
Specific gravity: 3.18
Cleavage : perfect octahedral
Refractive index: 1.434
Comments: Fluorite, calcium fluoride, is a major industrial mineral used as a flux in steel making as well as in the preparation of hydrofluoric acid and, in the ceramics industry, in glasses and enamels. Fluorite's vitreous, cubic crystals and cleavable, granular masses have a wide color range (often green, blue, or purple) and may fluoresce under ultraviolet light. Fluorite deposits form under a wide variety of conditions: as veins produced by hydrothermal alteration, as beds and cavities in sedimentary rocks, in hot spring deposits, and in pegmatites.

Fossilized Wood ... Quartz group
subtypes/ trade names: Agatized wood; Petrified wood, (brown, gray, red, white); some opal can be found in this;
Comments: look under quartz

Franklinite {frank'-lin-ite} see magnetite, loadstone
Crystallography: isometric
Colors: black
Hardness: 5.5 - 6.5
Specific gravity: 5.2
Cleavage: none
Comments: Franklinite is a zinc and iron manganese OXIDE MINERAL, that occurs abundantly only at Franklin, N.J., where, associated with zincite and willemite, it has been mined as an ore of zinc and manganese. A member of the SPINEL group, franklinite forms brilliantly metallic, iron black octahedral crystals, rounded grains, and granular masses in strongly altered limestone. Streak is reddish brown.

GGG...cubic..Gadolinium gallium garnet
colorless
Hardness: 6.5 - 7
Specific gravity: 7.02 - 7.05
Cleavage:
Refractive index: 2.03
Occurrence: man made
Crystal or stone size: thumb size

Gabbro...{gab'-roh}.. rock
Comments
Gadolinite...beryllium iron yttrium silicate
Crystal sys: monoclinic
Color: green, brown
SG: 4 - 4.47
Hardness: 6.5 - 7
Comments: ore of yttrium, thorium and rare earth elements

Galena {guh-leen'-uh}.. galenite .. lead sulfate
Crystallography: cubic - hexoctahedral
Colors:gray
Luster: metallic
Hardness: 2.5 - 2.75
Specific gravity: 7.4 - 7.6
Cleavage: perfect cubic
Crystal or stone size: massive
Comments
Garnet see type: almandine, pyrope, hessonite(essonite), grossular, demantoid, topazolite, spessartine (sp), andradite, audradite(sp) Almandine (rhodolite) uvarovite (a rare intensely green stone)
Colors : Green, to red, violet tint, brown tint

Garnierite ... see serpentine

Geode ... hollow rock .. sometimes lined with crystals .. see agate

Geyserite ... see opal

Glass
Glauberite {glow'-bur-yt} sodium calcium sulfate
Crystallography: monoclinic
Colors: white, light yellow, gray to buff
Luster: glassy
Hardness: 2.5 - 3
Specific gravity: 2.7 - 2.8
Cleavage: perfect basal
Occurrence: in and around salt beds
Crystal or stone size: small 2 to 3 cm
Comments: The EVAPORITE mineral glauberite, a sodium and calcium sulfate, occurs sparingly in the deposits left by evaporation of saline lakes. It forms brittle, tabular, and prismatic crystals with vitreous luster, pale yellow or gray color, good basal cleavage, and slightly salty taste. Glauberite also occurs as isolated crystals in clastic sedimentary rocks, volcanic cavities, and fumaroles.
Glaucodot ... cobalt iron arsenic sulfide
Crystal sys: orthorhombic
Color: white or grayish white often with pink erythrite
SG: 6.04
Hardness: 5
Comments: ore of cobalt

Glauconite ... hydrous potassium aluminum iron magnesium silicate
Crystal sys: monoclinic
Color: light blue green
SG: 2.5 - 2.8
Hardness: 2 - 2.25
Comments: because of potassium content it is used in textile, sugar and brewing.
Glaucophane ... hydrous sodium magnesium aluminum silicate
crystal sys: monoclinic
Color: pale blue gray to dark blue and black
SG: 3.08 - 3.3
Hardness: 6 - 6.5
Comments: of interest to petrologist as a means of defining the metamorphic conditions in which the surrounding rock formed.
Gneiss...{nys}...rock .. less mica than schist otherwise much the same
Crystal or stone size: massive
Comments
Goethite...{guh'-tyt}... hydrogen iron oxide
Crystallography: orthorhombic
Colors: black to brown to yellow
Luster: adamantine to metallic to silky
Hardness: 5 - 5.5
Specific gravity: 3.3 - 4.3
Cleavage: side pinacoid
Comments: The widespread iron ore mineral goethite, an iron hydroxide is a common weathering product. It usually forms stalactitic masses with concentric or radiating internal structure. Color is yellowish to dark brown. Streak yellow. Cleavage perfect. Goethite is often associated with and indistinguishable from limonite in the gossan of sulfide mineral deposits, in tropical laterite, and in bog deposits
Gold
Crystal sys: isometric
Color: yellow
SG:15.3 - 19.3
Hardness: 2.5 - 3
Comments,
Granite..{gran'-it}... coarse grained plutonic rock
Color: light gray, white, pink or black and yellow brown
Comments
Granodiorite Comments: Granodiorite is a plutonic rock composed mainly of coarse plagioclase, QUARTZ, and a little potassium FELDSPAR. Hornblende (see AMPHIBOLE) and biotite (see MICA) may constitute about 20 percent of the rock, with small amounts of other accessory minerals. Granodiorite is intermediate between QUARTZ MONZONITE and quartz DIORITE. Batholiths in the Sierra Nevada containing large amounts of granodiorite often show intrusive relationships. They probably formed from the melting or transformation of sedimentary rocks in deep zones of mountain belts.
Granophyre ... igneous rock
Color: reddish to pink
Comments: potassic feldspar, quartz. with: biotite, amphibole, sodic pyroxene, magnetite, ilmenite, muscovite, apatite, zircon, molybdenite, topaz, fluorite, etc.
Graphite ... carbon
Crystallography: hexagonal
Colors: black
Luster: submatallic
Hardness: 1 - 2
Specific gravity: 2.3
Cleavage: perfect basal
Crystal or stone size: rare tiny crystals in marble.
Comments: greasy feel

Graywacke...{gray'-wak}
Comments: Graywackes are SANDSTONES composed of a mixture of abundant mineral and rock fragments, together with a fine grained clay matrix that constitutes from 15 to 50 percent of the rock. Graywackes vary widely in their mineral composition and may include fragments of biotite, chlorite, feldspar, hornblende, magnetite, pyroxene, quartz, and serpentine. Their color, as the name implies, is various shadings of gray. Graywacke beds, probably formed by DENSITY CURRENTS, are thin and graded, and they are generally found in geosynclinal areas of thick sediment accumulation. They date from nearly all geological ages, from the Precambrian Time to the Pleistocene Epoch.
Greenockite ... cadmium sulfide
Crystal sys: hexagonal
Color: yellow
SG: 4.9
Hardness: 3 - 3.5
Comments: ore of cadmium

Grossularite ... grossular ...garnet Occurrence: metamorphosed limestone

Gummite ... a mixture of several uranium oxides silicates, and salts
Crystallography: none
Colors: orange red to gray, yellow
Luster: greasy to waxy
Hardness: 2.5 - 5
Specific gravity: 3.9 - 6.4
Cleavage: none
Comments: ore of uranium

Gypsum {jip'-suhm} alabaster .. hydrous calcium sulfate
Crystallography: monoclinic
Colors: white and light tints may be dyed
Luster: glassy to greasy to silky
Hardness: 2
Specific gravity: 2.3
Cleavage: one direction perfect
Occurrence: world wide
Crystal or stone size: massive
Comments: Gypsum, a hydrated calcium SULFATE MINERAL, is used as a raw material in plaster of Paris, as fertilizer, as an ornamental stone (alabaster and satin spar), and as optical material (selenite). Common gypsum is found as prismatic, curved, or twisting monoclinic crystals of vitreous luster and as earthy, foliated, or granular masses; alabaster as fine grained masses; selenite as colorless, transparent crystals or foliated masses; and satin spar as pearly, fibrous masses. Gypsum is soft clear, white, or tinted, and has perfect cleavage in one direction. It occurs with halite and other evaporite minerals in extensive beds, often alternating with limestone and shale, deposited in seas or playa lakes.
Hackmanite .. see sodalite
Color: light pink to light yellow
Comments: this variety of sodalite, when exposed to SW UV causes yellow an colorless to change to bright orange for a very short time.
Halite ... {hay'-lite}...salt
Crystallography:isometric
Colors: white, tinted blue, reddish
Luster: glassy
Hardness: 2.5
Specific gravity: 2.1 - 2.6
Cleavage: perfect cubic
Crystal or stone size:
Comments: Halite, sodium chloride (NaCl), is the most abundant of the EVAPORITE minerals. As rock salt, it is a major source of sodium and chlorine; as table salt, it is used to flavor food and is an essential dietary constituent Halite forms glassy, colorless, bluish or variously tinted cubic crystals and masses exhibiting perfect cubic cleavage Halite occurs with anhydrite, gypsum, and other evaporites, often in extensive beds left behind by evaporation of enclosed, salt water bodies (playas). When such deposits are buried and deformed, a plug or SALT DOME may be extruded through the overlying sediments. water soluble sometimes red fluorescent.

Hambergite
Colors: colorless
Hardness: 7.5
Specific gravity: 2.35
Refractive index: avg. 1.587 v. .072
Comments: strong double refraction, collector stone @ $100 to $300 per ct. for outstanding faceted stones.
Harmotome ... hydrated barium potassium aluminum silicate
Crystal sys: monoclinic
Color: white, gray, yellow, red or brown
SG: 2.4 - 2.5
Hardness: 4.5
Comments: collector item

Hauerite ... manganese sulfide
Crystal sys: isometric
Color: blackish brown
SG: 3.5
Hardness: 3.5 - 4.5
Comments: scientific interest

Hausmannite ... manganese oxide
Crystal sys: tetragonal
Color: blackish
SG: 4.7 - 4.8
Hardness: 5 - 5.5
Comments: manganese ore

Hauyne ... sodium calcium aluminum silicate sulfate
Color: blue, white, green
SG: 2.44 - 2.5
Hardness: 5.5 - 6
Comments: found in lapis, collector stone when it can be found large enough to cut. rare $ 2000 to $ 3000 per ct. blue
Hedenbergite ... calcium iron silicate
Crystal sys: monoclinic brown to light green
SG: 3.58 - 3.6
Hardness: 5 -6
Comments: collector item

Heliodore ... see beryl
Heliolite .. see feldspar
Color: brownish orange

Hematite...{hee'-muh-tite}...haematite
Crystallography: hexagonal
Colors: metallic black, reddish
Luster: high
Hardness: 5.5-6.5
Specific gravity: avg. 5.1
Cleavage: none
Refractive index:
Occurrence: iron ore
Crystal or stone size:
Comments: The widespread iron oxide hematite is the most important ore mineral of IRON. Other uses include polishing compounds and paint pigments. Varying in color from reddish brown to black, it forms brilliantly metallic, tabular crystals as well as compact, fibrous kidney shaped or granular masses and CONCRETIONS. Streak is cherry red to brownish. Present in rocks of all types as an alteration product of earlier iron minerals, hematite is particularly abundant in the sedimentary rocks known as RED BEDS. It is usually slightly magnetic.

Hemimorphite {hem-i-mohr'-fyt} calamine hydrated zinc silicate
Crystallography: orthorhombic
Colors: white stained
Luster: glassy
Hardness: 4.5 - 5
Specific gravity: 3.4 - 3.5
Cleavage: prismatic
Crystal or stone size: 2 - 3 cm.
Comments: The hydrated zinc silicate mineral hemimorphite, formerly called calamine, is an important ore of zinc. It forms rounded aggregates of white or tinted sheaf like crystals with perfect cleavage in one direction. Luster is vitreous. An alteration product of sphalerite, it occurs with other zinc minerals, particularly smithsonite, from which it is distinguished by its strong pyroelectricity. Fluoresces bright orange in LW UV.

Herderite ... calcium beryllium phosphate
Crystal sys: monoclinic
Color: yellow, greenish white, purple
SG: 2.9 - 3
Hardness: 5 - 5.5
Comments: collector item

Heubnerite ... see ferberite

Heulandite ... hydrated sodium calcium aluminum silicate
Crystal sys: monoclinic
Color: yellow, green, reddish orange
SG: 2.2
Hardness: 3.5 - 4
Comments: collector item

Hexagonite ... tremolite .. see actinolite

Hiddenite...spodumene...kunzite
Colors: light red to purple, colorless to yellow
Hardness: 6.5
Specific gravity: 3.18
Cleavage: perfect in two directions
Refractive index: avg.1.665
Birefringence:
Pleochroism: strong in colorless, red to violet colors in the dichroscope and to the eye as the stone is turned. Hiddenite shows blue green and yellow green. The yellow type shows differences in depth of color as you turn the stone.
Comments: biaxial +;

Hornblende
Crystallography: monoclinic
Colors: green (adenine); blue green (parasite) to black
Luster: glassy
Hardness: 5 - 6
Specific gravity: 3 - 3.4
Cleavage: prismatic
Occurrence: A mineral of metamorphic and igneous rocks, often replacing pyroxene (uralite ),also in solid crystalline aggregates.
Crystal or stone size: often several in. long
Comments: Fusible to a black glass.

Hornfels...{hohrn'-felz} rock
Comments: Hornfels is a fine grained, dense to granular METAMORPHIC ROCK formed mainly from sedimentary rocks and volcanic tuffs in the zones of contact metamorphism surrounding igneous intrusions. Hornfels can form at temperatures ranging from 200 deg to 800 deg C (1,392 deg to 1,472 deg F), depending on the depth and pressure, which respectively, cannot exceed 10 km (6 mi) and 3,000 bars. Recrystallization is as thorough as that of SCHIST but, because uniform pressures prevail during contact metamorphism, foliation does not occur. The texture is a mosaic of equal sized small grains. Mineralogic varieties are indicated by prefixing the term hornfels with the names of essential constituents, for example, biotite hornfels.
Hyacinth ... see zircon
Hyalite ... see opal

Hypersthene...Magnesium iron silicate..bronzite
Crystallography: orthorhombic
Colors: brown to black
Luster: bronze
Hardness: 5 - 6
Specific gravity: 3.4 - 3.9
Cleavage: perfect in one direction
Refractive index: 1.69 - 1.705
Crystal or stone size: good crystals are rare Comments: difficult to distinguish from augite. rock forming mineral. same as but with more iron than enstatite.
Idocrase...{y'-duh-krays}...vesuvianite .. Californite
Crystallography: aggregate of tetragonal xtals
Colors : yellow, green, brown
Luster: similar to jade
Hardness: 6.5 (Californite: 5.5)
Specific gravity: 3.38 (Californite: 3.3)
Cleavage: none
Refractive index: avg. 1.7 v. .015
Crystal or stone size: crystals very small aggregate massive
Comments: Californite resembles jade. Idocrase, or vesuvianite, is a calcium aluminosilicate mineral commonly found in altered limestones. It forms prismatic crystals ( tetragonal system ) and columnar, granular, or massive aggregates that are usually brown or green. Luster is vitreous to resinous, Transparent crystals sometimes are cut as gemstones, and californite, a compact, green, jadelike variety found in California, is an ornamental stone.

Ilmenite...{il'-muhn-yt}...iron titanium oxide
Color: dark brown to black
SG: 4.5 - 5
Hardness: 5 - 6
Comments: The iron and titanium oxide mineral ilmenite is present in small amounts in many igneous rocks and placer sands and is the principal titanium ore. Ilmenite forms iron black, thick tabular or acute rhombohedral crystals (hexagonal system), as well as thin plates, compact masses and embedded grains. Luster metallic to dull.
Iron pyrite ...see pyrite

Iolite...(see
cordierite)...dichroite

Ison glass...see mica

Jadeite
Crystallography: monoclinic
Colors: green, white, brown, mauve, black orange red, yellow
Luster: waxy
Hardness: 6.5 - 7
Specific gravity: 3.33 v. .04
Cleavage: two directions perfect, but the aggregate structure does not easily cleave in ant direction.
Refractive index: avg. 1.66 - 1.68 v. .012
Crystal or stone size: massive
Comments

Jasper
Subtypes / trade names: Agate (name used by some, Quartz group), Egyptian; Riband; Basanite; Blood; Nunkirchner; Plasma; Silex; also see quartz
Crystallography: none
Colors: all
Hardness: 7
Specific gravity: 2.55
Refractive index: avg.1.65
Crystal or stone size: massive
Comments: Jasper is an opaque and fine grained quartz. Colored red, yellow, brown, or off white to gray by impurities, jasper has long been used as an ornamental stone because it takes a fine polish. The color of a streak made on a black jasper touchstone can determine with good accuracy the gold content of gold ores.
Jet... coal
Crystallography: amorphous
Colors: black
Luster: glassy dull
Hardness: 2.5
Specific gravity: 1.33
Refractive index:avg. 1.66
Crystal or stone size:
Comments: hot point test produces coal odor
Kaolinite
Crystallography: monoclinic
Colors: white
Hardness: 2 - 2.5
Specific gravity: 2.6
Cleavage: can be cut and shaped
Occurrence: A mineral derived from aluminum silicates in the soil that has altered from feldspar in granite and pegmatite. Clay beds.
Crystal or stone size: compact masses, dull and earthy white, stained red brown to black. Clay like
Comments
Kernite...see hematite

Kimberlite...{kim-bur-lite}

Kornerupine... also cat's eye
Crystallography: orthorhombic
Colors: green, brownish green, yellow
Hardness: 6.5
Specific gravity: 3.32
Refractive index: avg. 1.675
Birefringence: .013
Occurrence: Sri Lanka, Burma, Kenya
Crystal or stone size:
Comments: strongly dichroic;confused w/tourmaline biaxial -

Kunzite ...(see spodumene)

Kyanite
Crystallography: triclinic
Colors: blue, some green, colorless
Hardness: 4 in one direction to 7 in the other
Specific gravity: 3.69
Cleavage: easy in one direction
Refractive index: avg. 1.72 v. .019
Pleochroism: strong; colorless, dark blue violet and blue.
Occurrence: can be found in NC
Crystal or stone size:
Comments: biaxial - The aluminum SILICATE MINERAL kyanite (derived from the Greek kyanos, meaning "blue") is used in the manufacture of spark plugs, porcelain, and other refractories; it has the same chemical composition as ANDALUSITE and SILLIMANITE. Its long bladed, usually blue crystals are distinctive. Luster is vitreous to pearly. Cleavage is perfect in one direction. Kyanite occurs in GNEISSES, SCHISTS, and granite PEGMATITES; it is an indicator of deep-seated, regional metamorphism of clay rich sediments.

Labradorite...(see feldspar)
Crystallography: triclinic
Colors: white, yellow, reddish, gray to black
Luster: glassy
Hardness: 6 - 6.5
Specific gravity: 2.6 - 2.8
Cleavage: good in two directions
Occurrence: labradorite (sp) found in Labrador
Crystal or stone size: not common except albite (cleavelandite), moonstone
Comments: bluish to whitish internal flashes in moonstone and labradotite

Lamprophyre...{lam'-proh-fire}
Comments: Lamprophyre is a dark-colored igneous rock composed of large crystals (phenocrysts) of iron and magnesium-rich minerals, such as hornblende (see AMPHIBOLE), biotite (see MICA), or PYROXENE, set in a fine grained, dark-colored groundmass. Lamprophyres commonly occur as dikes or sills. Most of them contain less than 46% silica by weight and are high in sodium and potassium. Lamprophyric magma is commonly rich in volatile compounds such as water and carbon dioxide.
Latite...{lay'-tite}
Comments: Latite is a medium colored igneous rock composed of large crystals of plagioclase and potassium feldspar set in a fine grained groundmass. Latites commonly occur as dikes or sills. Chemically, latite is a fine grained equivalent of monzonite.

Lapis lazuli...{lap'-is laz'-u-lee} lazurite, lazulite, scorzalite
Crystallography: monoclinic
Colors: blue
Luster: waxy
Hardness: 5.5
Specific gravity: 2.8
Cleavage: poor
Refractive index: 1.5
Crystal or stone size: massive

Lazulite...hydrous magnesium aluminum phosphate
Crystal sys: monoclinic
Color: blue
SG: 3 - 3.1
Hardness: 5 - 6
Comments: ornamental stone

Lazurite ... sodium calcium aluminum silicate sulfate
Crystal sys: tetragonal
Color: blue, white, gray, pink
SG: 2.55 - 2.74
Hardness: 5 - 6.6
Comments: collector item

Leadhillite...sulfate & carbonate of lead... Pb4(SO4)(CO3)2(HO)2
Crystal: monoclinic (looks like hexagonal)
Color: white tinged with yellow, blue, or green Luster: pearly to adamantine
Cleavage: prominent, almost micaceous
Hardness: 2.5
SG: 6.3 - 6.4
Fracture: conchoidal
Translucent to transparent
Comments: fluoresces orange

Legrandite ...see adamite

Lepidocrocite...see hematite

Lepidolite...basic fluosilicate of lithium, potassium, and aluminum

Leucite...potassium aluminum silicate
Colors: colorless
Hardness: 6
Refractive index: 1.504 - 1.509
Crystal or stone size:
Comments: some color caused by thin repeated twinning laminate

Lepidocrocite ... hydrous iron oxide
Color: red, brown
SG: 4
Hardness: 5 - 5.5
Comments: iron ore

Lepidolite...hydrous potassium lithium aluminum
Ver: zinnwaldite, silver gray to brown silicate
Color: pink to lilac
SG: 2.8 - 2.9
Hardness: 2.5 - 4
Comments: ore of lithium

Leucite...potassium aluminum silicate
Color: white
SG: 2.5
Hardness: 5.5 - 6
Comments: fertilizer

Libethenite...copper phosphate... Cu2(OH)PO4
Crystal system: rhombic bipyramidal
Color: dark olive green
Luster: resinous
Hardness: 4
SG: 3.6 - 3.8
Fracture: subconchoidal
Cleavage: 2 good
Comments: Like olivenite, brochantite, and malachite, (likely associations), is one of the secondary minerals formed in the alteration through weathering of sulfide ore minerals.

Lignite ... coal
Color: black

Limonite...{ly'-muh-nite}...stalactites...goethite
Crystallography: orthorhombic or amorphous
Colors: brown black to ocher yellow
Luster: glassy to dull
Hardness: 5.5
Specific gravity: 2.7 - 4.4
Cleavage: none
Crystal or stone size:
Comments
Limestone...rock... calcium carbonate (calcite) in a very fine granular structure
Color: gray
Hardness: 3
SG: approx 2.7
Cleavage: brittle
Comments: Limestone is easy to scratch acid will dissolve. some limestone was chemically precipitated, other in beds of accumulated lime removed from seawater by living organisms. Beds of clean limestone can only form father out in the sea and in deeper water beyond the distance that stream borne clay particles and sand can travel. Often remains of the organic life of the sea of the period of the lime deposition are included in the beds. These are fossils.

Linarite...hydrous lead copper sulfate
Color:blue
Crystal sys: monoclinic
SG: 5.35
H: 2.5
Comments: crystals to 4 in.

Lindgrenite...see powellite

Lintonite...(sp) local name in Michigan
Color: green to grayish green
Hardness: 5 - 5.5
Comments: sometimes confused with jade
Liroconite...hydrated copper aluminum arsenate... Cu2Al(AsO4)(OH)4.4H2O
Crystal system: monoclinic - prismatic
Color: sky blue to greenish blue
Luster: glassy
Hardness: 2 - 2.5
SG: 3
Streak: pale blue
Cleavage: 2, poor, brittle.
Comments: translucent. Blowpipe turns it deep blue, then blackens, fusing to a black bead. Soluble in acid.

Lithiophilite...isomorphous series of lithium, iron, and manganese phosphate LiMnPO4 (Triphylite LiFePO4)
Crystal system: orthorhombic
Color: gray blue to gray blue green (triphylite), pink to greenish brown (lithiophilite)
Luster: glassy
Hardness: 4.5 - 5
SG: 3.4 - 3.6
Cleavage: 1 fair, 2 imperfect
Fracture: uneven to small conchoidal
Comments: Brittle, transparent to translucent. Fuse on charcoal to black bead. Triphylite bead magnetic.

Lithophysae...see cristobalite & tridymite (polymorphs of quartz)

Loadstone ... see magnetite
Color:black to dark brown

Loellingite...FeAs2... diarsenide of iron
Crystal system: orthorhombic - bioyramidal
Color: tin white
Luster: metallic
Hardness: 5 - 5.5
SG: 6.2 - 8.6
Cleavage: basal
Varieties: nickelin, cobaltian loellingite
Comments: sometimes found with cobalt and nickel. Arsenic approx. 68 %; when heated gives garlic odor
Luzonite... see enargite

Magma... melted rock well below the surface of the earth; called lava when it reaches the surface.
Magnesite ... magnesium carbonate
Crystal sys: hexagonal
Color: white, yellow, gray
SG: 3
Hardness: 3.5 - 4.5
Comments: The carbonate mineral magnesite is a source of magnesia, used in the manufacture of refractory brick and various chemicals and pharmaceuticals. Color is white (gray-to-brown with impurities), Luster is vitreous. A compact, earthy form occurs when carbonic acid alters rocks containing serpentine or peridotite; a cleavable (rhombohedral) aggregate form occurs when metamorphism alters magnesium rich rocks, or when magnesium solutions replace limestone rocks. Major deposits are in Manchuria, Austria, Washington, and Nevada.

Magnetite ... iron oxide
Color: black
SG: 5.2
Hardness: 5.5 - 6.5
Comments: ore of iron, strongly magnetic
Malachite...copper carbonate

Malacolite ... see diopside & hedenbergite
Manganapatite...see apatite

Manganite...manganese oxide... MnO(OH)
Crystal system: monoclinic - prismatic
Color: steel gray to black
Luster: submatilic
Hardness: 4
SG: 4.2 - 4.4
Streak: reddish brown
Cleavage: perfect side, poor prismatic and basal
Comments: Formed at higher temps than other manganese oxides, in veins.

Manganocolumbites...see columbite & tantalite
Manganotantalites...see columbite & tantalite
Marble...forms in regional metamorphism from another single mineral sedimentary rock, like sandstone is a rock in which no major change can take place other than a growth and cementation of the individual crystal units. Marble forms from limestone and dolomite.
Color: multi colored depending on containts
Hardness: 3 - 4.5

Marcasite Crystallography: orthorhombic
Colors: silver black
Luster: metallic
Hardness:6
Specific gravity: 4.9

Margarite ... hydrous calcium aluminum silicate
Color: pink, white or grat aggregates
SG: 2.99 - 3.1
Hardness: 3.5 - 4.5
Comments: can be found in NC, PENN, collector item
Marialite...sodium & calcium aluminum silicate, with chlorine, carbonate, and sulfate; sodium and calcium mutally replace each other to any amount, making a series which have been named marialite for the NaCl rich end member and meionite for the CaCO end
Crystal system: tetragonal
Color: colorless - white, violet, pink, gray
Luster: glassy
Hardness: 5.5 - 6
SG: 2.5 - 2.7
Comments: fluorescent orange to bright yellow, less often red.

Marl
Comments: A sedimentary rock, marl is a white, gray, or brownish earthy mixture of fin grained calcium carbonate and clay. Formed in both marine and freshwater environments marl commonly contains fossil shells. It is used as a fertilizer and in the manufacture of insulation, portland cement, and bricks. Some marl, such as the potassium rich glauconite, or green sand, marl of the Atlantic coasts of Europe and the United States, is used in water softeners.
Marmolite...see serpentine

Marshite...see calomel

Martite...see magnetite

Massicot... PbO...Litharge...PbO lead oxide
Crystal system: rhombic
Color: yellow to red
Luster: greasy to dull
Hardness: 2
SG: 9.7
Cleavage: several
Comments: association with galena

Melanite ... see andradite

Melanterite...see chalcanthite

Meneghinite...see jamesonite

Mercury ... Hg
Color: silver
SG: 13.6
Hardness: soft heavy liquid
Comments (there are a lot of them...)
Mesolite ... see natrolite

Meteorite ... see iron and pyrrhotite
Miargyrite...antimony sulfide ...AgSbS2
Crystal system: monoclinic
Color: black to gray
Luster: metallic
Hardness: 2 - 2.5
SG: 5.1 - 5.3
Streak: cherry red
Cleavage: 3 poor
Fracture: subconchoidal
Comments: rare, never forming large crystals. Silver ore.
Mica group...{my'-kuh}...muscovite...biotite...phlogopite
Crystallography: monoclinic prismatic
Colors: colorless, light yellow, amber, rose, green, gray, black
Luster: glassy
Hardness: 2 - 2.5
Specific gravity: 2.8 - 3
Cleavage: perfect basal
Crystal or stone size: common flat transparent used as windows in stoves; plates are flexible.
Comments
Micaceous hematite
Comments: see hematite; hematite with mica.
Mica schist...conglomerate rock containing a large amount of mica (see mica)

Microcline...(see feldspar)...green feldspar...amazonstone
Crystallography: triclinic
Colors: light cream, yellow, brown, green to black.
Luster: resinous
Hardness: 6
Specific gravity: 2.5 - 2.6
Cleavage: two directions good
Occurrence: pegmatite dikes
Crystal or stone size: inches to feet
Comments: gemstones and scouring powder
Microlite...hydrous sodium calcium tantalum oxide
Crystal sys: isometric
Color: brown, colorless, yellow
SG:4.2 - 6.4
Hardness: 5 - 5.5
Comments: VA,MA,CN, collector item

Migmatite...anatexite...ultrametamorphic rock
Colors: dark to light gray
Occurrence: Precambrian shields
Uses: building stone, sometimes as polished slabs for ornamental purposes.

Millerite ... nickel sulfide
Crystal sys: hexagonal
Color: brassy yellow
SG: 5.2 - 5.6
Hardness: 3 - 3.5
Comments: The nickel sulfide mineral millerite (NiS) is a minor ore of nickel. It forms slender to capillary, brass to bronze yellow crystals, often in radiating needles, interwoven hairs, or tufted coatings. Luster metallic, streak greenish black. A low temperature mineral, millerite occurs as a lining in cavities, geodes, and carbonate veins; as an alteration, or weathering, product of other nickel minerals; and as inclusions in other minerals.
Mimetite...{mim'-uh-tyt}...mimetesite...lead arsenate chloride
Crystallography: monoclinic
Colors: colorless, yellow brown to orange
Luster: resinous to adamantine
Hardness: 3.5
Specific gravity: 7.1
Cleavage: none
Crystal or stone size: small long crystals Comments: The lead arsenate mineral mimetite is a minor ore of lead, occurring in the oxidation zone of lead veins. Its name is derived from its ability to "mimic" pyromorphite, a similar but more common mineral in which the arsenic is replaced by phosphorus. Mimetite forms crusts and prismatic or barrel shaped crystals (hexagonal system) that are pale or orange yellow to brown. Luster, resinous; and its an ore of lead.
Minium...see massicot

Mispickel...arsenopyrite
Crystallography: monoclinic
Colors: sliver white
Luster: metallic
Hardness: 5.5 - 6
Specific gravity: 5.9 - 6.2
Cleavage: prismatic
Crystal or stone size:
Comments: garlic smell with hammer blow, ore of arsenic

Moldavite...tektites from Czechoslovakia
Colors: gray, black, green
Luster: glassy
Hardness: 5
Specific gravity: 2.35
Refractive index: 1.49
Crystal or stone size:
Comments: volcanic glass

Molybdenite...{muh-lib'-duh-nyt}... molybdate
Crystallography: hexagonal
Colors: bluish gray
Luster: greasy
Hardness: 1 - 1.5
Specific gravity: 4.7
Cleavage: perfect along plates
Occurrence: tabular crystals with hex outline interwoven masses common
Comments: The chief ore of molybdenum is the molybdenum sulfide mineral molybdenite. Usually found in foliated or granular masses and scales, molybdenite occasionally forms lead gray, six sided tabular or prismatic crystals. Its luster is metallic. Because of its softness and perfect basal cleavage, it has a greasy feel and is useful in making special lubricants. Its streak (greenish or bluish gray). SG (4.7) distinguish it from graphite (dark black and 2.23), which has similar physical properties. Widespread but rarely abundant, molybdenite occurs in acid igneous rocks, such as granite in contact metamorphic deposits; in pegmatite; and in high temperature quartz veins. The world's most important deposit is at Climax, Colorado.

Monazite...{mahn'-uh-zyt}
Comments: The chief ore of thorium and the rare earths is the phosphate mineral monazite. It commonly forms small flattened or elongated crystals (monoclinic system) that are a resinous, reddish to yellowish brown. Hardness is 5 -5.5, streak is white, and specific gravity is 4.6-5.4. Monazite occurs as an accessory mineral in granites, gneisses, and pegmatites and as rounded grains in the sands formed from their weathering. The thorium-rich varieties are radioactive and have been used in geologic dating.

Monzonite...{mahn'-zuh-nyt} rock
Comments: The coarse-grained plutonic rock monzonite, which results from deep igneous or metamorphic processes, contains approximately equal amounts of potassium and plagioclase feldspars and little or no quartz. Dark minerals, such as pyroxene and hornblende, make up 30 to 40 percent of the rock. Monzonite is intermediate between syenite and diorite.

Moonstone...see albite, orthoclase (plagioclase feldspar)
Morganite...see beryl...mortor
Colors: rose pink to red, light pink to colorless
Hardness: 7.5
Specific gravity: 2.8
Refractive index: avg. 1.59 v. .008

Mossottite...see aragonite

Mottramite...(Zn,Cu)Pb(VO4)(OH)... lead zinc - copper ...Descloizite...(Cu,Zn)Pb(VO4)(OH)
Crystal system: rhombic
Color: yellow brown to cherry red, brown, green, or black
Luster: greasy
Hardness: 3.5
SG: 5.9 mottramite... 6.2 descloizite
Streak: yellow orange to brown red
Fracture: small conchoidal
Cleavage: none
Comments: associated with wulfenite and vanadinite
Muscovite...var. fuchsite, alurgite, mica ...hydrous potassium aluminum
Crystallography: monoclinic
Colors: silver white, yellow, gray, brown
Luster: glassy
Hardness: 2 - 2.5
Specific gravity: 2.76 - 2.88
Cleavage: perfect along plates
Crystal or stone size: tabular crystals w/pseudo -hex outline, up to 30 - 50 sq. yds.
Comments: usually scaly laminae masses
Mylonite...{my'-luh-nyt}
Comments: Ductile, as opposed to brittle, processes dominate the formation of the metamorphic rock mylonite in deep seated fault zones. Mylonite is commonly foliated and may contain fine grained quartz, feldspar, and micas surrounding much larger feldspar or sometimes quartz grains or other minerals that have been greatly flattened and drawn out in the foliation. Mylonite zones, which may vary in width from a few millimeters to several kilometers, occur in the central portions of recent mountain chains and in the roots of old mountain chains.

Nantokite...see calomel

Naphtheline...(sp) Nepheline, igneous rock .. nephelin w/ olivine augite, titnite, perovskite, melilite noselite, sodalite, or hauyne.
Crystallography: none
Colors: light gray, pin, green
Hardness: ver.
Specific gravity: ver.
Crystal or stone size: massive
Comments: Nepheline, the most common of the group, is a white to gray mineral that is distinguished from the feldspars, which it resembles, by its poorer cleavage and slightly greasy luster. It occurs as grains or large masses in many alkaline igneous rocks ranging from magnesium rich nepheline basalts to granitelike but quartz free nepheline syenites. It is also found in some metamorphic rocks, particularly the nepheline gneisses of Ontario, Canada.
Natrolite...hydrated sodium aluminum silicate
Crystallography: orthorhombic
Colors: white
Luster: vitreous to pearly
Hardness: 5 - 5.5
Specific gravity: 2.2 - 2.26
Crystal or stone size: 3 ft. x 6 in. in Canada
Comments: found with asbestos, collector mineral
Nephrite ... tremolite ... actinolite...(jade)
Crystallography: monoclinic
Colors: green, white, black
Hardness: 6.5
Specific gravity: 2.96
Refractive index: 1.62
Comments: usually classed with jadeite as jade.
Neptunite ... sodium potassium iron titanium silicate
Color: dark brown to black
SG: 3.23
Hardness: 5-6
Comments: collector item

Niccolite ... nickeline .. nickel arsenide
Crystallography: hexagonal
Colors: pink bronze, pale green film
Luster: metallic
Hardness: 5 - 5.5
Specific gravity: 7.78
Cleavage: none
Crystal or stone size: rare small crystals
Comments: ore of nickel

Nicholsonite...see aragonite

Nickeline ... see niccolite

Niter... potassium nitrate (saltpeter) ...KNO3
Color: white
Luster: glassy
Hardness: 2
SG: 2.1
Comments: found in caves, short fibers on rock surface and floors.
Norbergite

Obsidian...volcanic glass
Crystallography: none
Colors: black
Luster: glassy
Hardness: 5
Specific gravity: 2.35
Cleavage: none
Refractive index: 1.49
Occurrence: lava flows
Crystal or stone size: can be massive
Comments
Octahedrite ... see anatase

Odontolite ... very similar to turquoise
Colors: blue green
Hardness: 5
Specific gravity: 3.1
Refractive index: 1.6
Crystal or stone size:
Comments: can be confused with turquoise
Oligoclase...(see feldspar)

Olivine...olivenite... magnesium iron silicate ...forsterite...fayalite ...gem variety peridot

Omphacite...calcium magnesium iron aluminum silicate
Crystal sys: monoclinic
Color: light green
SG: 3.29 - 3.37
Hardness: 5-6
Comments: collector crystal usual found in quartz
Onyx
Colors: white, usually dyed to any color
Hardness: 7
Specific gravity: 2.6
Refractive index: 1.535 + - .004
Crystal or stone size: massive
Comments: used for carvings, building stone
Opal ... black, fire, white, water

Ophiolite... see serpentine

Orpiment... arsenic sulfide
Color: golden yellow to orange
SG: 3.48
Hardness: 1.5 - 2
Comments: ore of arsenic, used in hide tanning
Orthite....(Allanite)
Orthoclase...orthose...(see feldspar)...moonstone ...plagioclase...albite...adularia
Colors: colorless with floating blue sheen, light yellow, white, see below
Hardness: 6 - 6.5
Specific gravity: 2.56
Cleavage: perfect in two directions
Refractive index: 1.52 - 1.526
Crystal or stone size:
Comments: 4 ray star in green, brown, orange, brown and black. It may be completely transparent, and the sheen can be either silvery white or a soft but distinct blue. The blue or white sheen is called adularscent, and is caused by the presence of tiny crystals of albite arranged in layers within the host microline. The adularscent sheen resembles a cloud of light that appears within the gem when it is turned at the right angle to the eye. Moonstones come mainly from India, Sri Lanka, Burma, Canada, Brazil, and others.

Painite
Colors: dark red
Hardness: 8
Specific gravity: 4.01
Refractive index: 1.8 +- .029
Pleochroism: pale brown orange to ruby red
Comments: uniaxial (-)

Pargasite... see hornblend

Pearl...white, pink, bronze, black, gray, blue... freshwater ... conch is pink, clam is black. Biwa (fresh water), Mabe (dome), baroque (odd shape)
Colors: white to cream, Australian is silver white, venezuelan is translucent

Pectolite

Pegmatite...{peg'-muh-tyt} ...igneous rock
Penninite ... see chlorite ... pennine
Pentlandite ...{pent'-luhnd-yt} see pyrrhotite
Comments: The nickel and iron isometric sulfide mineral pentlandite is the principal ore of nickel. Forming light bronze yellow, granular aggregates in basic igneous rock, it is nearly always intimately associated with and hard to distinguish from pyrrhotite. Hardness is 3.5, luster is metallic, streak is light brown, and specific gravity is 4.6-5.0. At nickel mines in Sudbury, Ontario, and elsewhere, the pentlandite pyrrhotite aggregate is crushed, and the pyrrhotite is magnetically separated from the nonmagnetic pentlandite.

Periclase... see brucite

Peridot ...(see olivine) Occurrence: green type from Red Sea, Arizona Burma, etc.

Peridotite...pyroxenite
Colors: green, blue, black
Occurrence: world wide
Comments: a rock, a dunite

Perlite...A glass froth which swells with heat or water found in old obsidian flows. A man product is sold as perlite.

Petalite ... lithium aluminum silicate
Crystallography: monoclinic
Colors: colorless, white
Luster: vitreous to pearly
Hardness: 6 - 6.5
Specific gravity: 2.41
Cleavage: perfect
Crystal or stone size:
Comments: ore of liyhium

Phacolite ... see chabazite

Phenacite...phenakite
Crystallography: hexagonal
Colors: colorless to white
Luster: glassy
Hardness: 7.5 to 8
Specific gravity: 2.96 to 3
Fracture: conchoidal
Cleavage: poor
Refractive index: avg. 1.662 v. .016
Occurrence: a mineral of pegmatites and high temperature veins.
Comments: bright silvery appearance.

Phlogopite... potassium, magnesium, aluminum silicate ...K(Mg,Fe)3(AlSi3)O10(F,OH)2
Crystal system: monoclinic - prismatic
Color: light to dark brown
Luster: pearly to metallic
Hardness: 2.5 - 3
SG: 2.7
Cleavage: perfect basal, yielding thin, flexible and elastic plates
Comments: translucent, 6 or twelve ray star not uncommon. Unlike muscovite makes a cloudy solution if boiled in strong sulfuric acid.
Phonolite ... igneous rock
Crystallography: none
Colors: light gray, green, brown, pink
Luster: greasy
Hardness: Varies
Occurrence: in US, COL, SD, MONT.
Crystal or stone size: massive
Comments: building stone

Phosgenite...chlorocarbonate of lead... Pb2(CO3)Cl2
Crystal system: tetragonal trapezohedral (4 2 2)
Color: colorless, white, yellowish brown to gray
Luster: adamantine
Hardness: 2.5 - 2.75
SG: 6 - 6.1
Fracture: conchoidal
Cleavage: good prismatic, poor basal
Comments: slightly sectile, transparent to translucent, fluoresces a brilliant orange yellow
Phosphophyllite ... hydrated zinc iron manganese phosphate
Crystallography: monoclinic
Colors: blue green
Luster: vitreous
Hardness: 3 - 3.5
Specific gravity: 3 - 3.1
Crystal or stone size: long prismatic or thick tabular crystals are rare up to 4 in.; massive
Comments: sometimes faceted into gems for collectors

Phosphuranylite

Phyllite

Picrolite...see serpentine

Pinite...see spodumene

Pisanite...see chalcanthite

Pisolitic ... see bauxite

Pitchblende ... see uraninite

Platinum
Color: silver gray
SG: 14 - 19
Hardness: 4 - 4.5
Comments
Plagioclase...see feldspar

Polybasite ... silver copper antimony sulfide
Crystallography: monoclinic
Colors: iron black
Luster: metallic
Hardness: 2 - 3
Specific gravity: 6 - 6.2
Crystal or stone size: small, collector
Comments: ore of silver

Polycrase... see monazite

Polyhalite

Porphyry ... igneous rock .. diorite
Crystallography: none
Colors: gray, green, reddish to bluish Hardness: varies
Specific gravity: varies
Comments: facing on buildings, marble like.
Powellite

Prehnite...{pray'-nyt}
Crystallography: orthorhombic
Colors: pale greenish yellow, yellow, white
Luster: glassy
Hardness: 6
Specific gravity: 2.87
Cleavage: basal
Refractive index: avg. 1.63 v. .03
Occurrence: N.J., CN, Mass., Quebec
Crystal or stone size: crystals usually small, stone massive.
Comments: The calcium-aluminum silicate mineral prehnite, which may be pale to dark green, gray, white, yellow, or colorless, is sometimes cut and sold as Cape emerald. Often associated with zeolite minerals, it usually lines the cavities of basaltic rocks. Prehnite frequently forms lamellar or rounded masses; tabular or prismatic crystals (orthorhombic system) are found more rarely. Ornamental stone that sometimes is confused with jade.
Proustite...{proost'-yt}...silver arsenic sulfide
Crystallography: hexagonal
Colors: dark red
Luster: adamantine
Hardness: 2 - 2.5
Specific gravity: 5.57
Cleavage: good rhombohedral
Refractive index:
Crystal or stone size: up to 6 in.
Comments: The silver arsenic sulfide mineral proustite, or light ruby silver, is a minor ore of silver. Scarlet to vermilion in color and streak, proustite forms compact masses and prismatic, rhombohedral, or scalenohedral crystals (hexagonal system) often associated with PYRARGYRITE, or dark ruby silver, in silver veins. luster is adamantine to submetallic. Prized mineral for collectors.

Psilomelane...{sy-loh-mel'-ayn}...romanechite .. hydrous barium manganese oxide
Crystallography: orthorhombic
Colors: brown, black
Luster: submetallic
Hardness: 5 - 7
Specific gravity: 3.7 - 4.7
Crystal or stone size: masses never in crystals
Comments: Psilomelane, a basic oxide mineral of barium and manganese, is, after pyrolusite, the most important manganese ore. It forms iron-black to steel-gray concretionary or earthy masses that have a submetallic or dull luster, streak brownish black. Formed by the weathering and alteration of manganese carbonates, psilomelane frequently is associated with pyrolusite and other secondary manganese oxides and with clay and hydrated iron oxides. Greasy feel.

Pumice...{puhm'-is}... igneous rock
Crystallography: none
Colors: gray, yellowish, red
Specific gravity: v. sometimes less than water
Occurrence: material expelled by volcanos
Crystal or stone size: massive
Comments: Pumice is a frothy volcanic glass, usually light in color and high in silica. It occasionally contains some crystals of quartz and feldspar. The froth, which forms during an eruption of a gas rich magma because of the decrease in confining pressure, is similar to the bubbles formed in carbonated beverages when their containers are opened. The bubbles make pumice so light that it will float on water. Pumice, which may float for weeks before it becomes waterlogged and sinks, has been found floating as many as 6,400 km (4,000 mi) from its source. Pumice is used primarily for abrasives, polishing compounds, insulators, and lightweight aggregates and in stucco, plaster, and cement. very porous, may float

Purpurite ... manganese iron phosphate
Crystal sys: orthorhombic
Color: purple to red with brown to black surface alteration
SG: 3.4
Hardness: 4 - 4.5
Comments: SD,CA collector item

Pycnite... see topaz

Pyralspite ... see garnet

Pyrargyrite... silver antimony sulfide
Crystallography: hexagonal
Colors: black w/dark red tints
Luster: submetallic
Hardness: 2.5
Specific gravity: 5.85
Crystal or stone size: masses or disseminated grains
Comments: purple red streak, minor silver ore
Pyrite...{py'-ryt}
Crystallography: cubic
Colors: brassy yellow
Luster: metallic
Hardness: 6
Specific gravity: 4.9 - 5.02
Cleavage: none
Comments
Pyrochlore ... see microlite

Pyrolusite ...manganese oxide... polianite Crystallography: tetragonal
Colors: black
Luster: greasy
Hardness: 6 - 6.5
Specific gravity: 4.7 - 5
Crystal or stone size: aggregates and masses
Comments: earthy ver. very soft and greasy ore of manganese

Pyromorphite ... lead phosphate chloride
Crystallography: hexagonal
Colors: green brown, colorless
Luster: resinous to adamantine
Hardness: 3.5 - 4
Specific gravity: 6.7
Cleavage: none
Occurrence: PENN., IN US
Crystal or stone size: aggregates and masses
Comments: minor ore of lead

Pyrope ...see garnet
...magnesium aluminum silicate
Crystallography: isometric
Colors: red, best is blood red
Luster: vitreous
Hardness: 7.5
Specific gravity: 3.7 - 3.9
Cleavage: none but splinters
Refractive index: 1.73 - 1.76
Crystal or stone size: gem, up to 20 cts
Pyrophanite...see Ilmenite

Pyrophyllite...{py-roh-fy'-lyt} hydrous aluminum silicate... var. agalmatolite, pagodite
Crystallography: monoclinic
Colors: yellow, white, pale green, brown
Luster: pearly to greasy
Hardness: 1 - 2
Specific gravity: 2.8
Occurrence: NC, SC, AR, GA. IN US
Crystal or stone size: massive, used for carving
Comments: flexible but not elastic. Pyrophyllite a hydrous aluminum silicate mineral, often resembles talc in its appearance, properties, and uses. It forms foliated, radiating, or fibrous aggregates and compact to granular masses that have a greasy feel and are pale colored. Mohs hardness is 1 to 2, luster is pearly to dull and glistening, and specific gravity is 2.65 to 2.90. Pyrophyllite is the main component of some schists and also occurs in hydrothermal veins with quartz and micas.
Pyroxenite ... igneous rock .. var. websterite, bronzitite
Contains: pyroxene with some or all of olivine, hornblende, chromite magnetite, ilmenite sulfide biotite, garnet, apatite.
Crystallography: none
Colors: dark green, brown, black
Crystal or stone size: massive, coarse grain
Comments: building stone

Pyroxmangite ... see rhodonite

Pyrrhotite ... ferrous sulfide
Crystallography: pseudohexagonal
Colors: bronze
Luster: metallic
Hardness: 4
Specific gravity: 4.6 - 4.7
Cleavage: none
Crystal or stone size: massive
Comments: magnetic

Quartz
Subtypes

Quartzite ... metamorphism of sandstone
Colors: brown, yellow, gray, reddish, white
Hardness: ver. see quartz
Specific gravity: ver.
Cleavage: none
Occurrence: world wide
Crystal or stone size: massive
Comments: very small grains of quartz firmly together

Radelerz ... see bournonite

Rammelsbergite... see loellingite

Realgar ... arsenic sulfide
Crystallography: monoclinic
Colors: orange red
Luster: resinous
Hardness: 1.5 - 2
Specific gravity: 3.4 - 3.5
Cleavage: perfect
Crystal or stone size: crystals common
Comments: could be mistaken for cinnabar ore of arsenic, very unstable
Rhodochrosite...{roh-duh-kroh'-syt}...manganese carbonate
Crystallography: hexagonal
Colors: pink, gray, brown
Luster: vitreous to pearly
Hardness: 3.5 - 4
Specific gravity: 3.4 - 3.6
Cleavage: perfect rhombohedral
Refractive index: 1.597 - 1.817
Crystal or stone size: massive
Comments: ornamental stone, crystals rare. The manganese carbonate mineral rhodochrosite is a minor ore of manganese used mainly as a decorative stone and gemstone. Typically displaying shiny rose-red, intricately banded surfaces, it forms granular to compact cleavable masses, crusts, or columns. Streak is white. It occurs in moderate to low-temperature hydrothermal ore veins, particularly of silver, lead, zinc, and copper, as well as in high temperature metamorphic deposits.

Rhodonite...{roh'-duh-nyt}...manganese silicate
Crystallography: triclinic
Colors: violet red to flesh red
Hardness: 5.5 - 7
Specific gravity: 3.3 - 3.68
Cleavage: two directions perfect
Refractive index: 1.72 - 1.744
Crystal or stone size: massive
Comments: ornamental stone usually with black inclusions. The manganese, iron, and calcium silicate mineral rhodonite is valued not only as a rose-red ornamental stone but also as a major ore of manganese in India. Usually associated with rhodochrosite and other manganese minerals, it forms large, rounded, tabular crystals (triclinic system) or cleavable, compact masses. luster is vitreous, streak is white.

Rhodolite ...see
garnet
Colors: violet red to brownish red violet
Specific gravity: 3.84
Refractive index: 1.76
Comments: a cross between almandite & pyrope
Rhyolite ... a volcanic rock
Colors: shades of gray, yellow, pale to deep red
Luster: glassy
Hardness: 6 - 6.5
Specific gravity: v.
Occurrence: volcanic
Crystal or stone size: massive
Comments: it may contain many minerals, biotite quartz, hornblende, opal, feldspar, magnetite. Rhyolite is a light-colored, fine grained volcanic rock with a very high (more than 70%) silica content. It often contains phenocrysts of quartz and feldspar in a glassy matrix. Iron and magnesium minerals are rare or absent. Similar to the coarser grained granites in mineralogy and chemistry, rhyolite tends to be very viscous because of its high silica content, and upon eruption it generally forms steep-sided domes and plugs. Gas rich rhyolite, however, erupts violently to form welded tuffs, or ignimbrites, and may spread out over great distances.

Richterite ... hydrous sodium magnesium silicate
Color: purple red to yellow
SG: 2.97 - 3.46
Hardness: 5-6
Comments: in crystal form a collector item
Rockbridgeite... see dufrenite

Rosolite
Crystallography: monoclinic
Colors: deep rose to pink
Luster: glassy
Hardness: 3.5
Specific gravity: 3.5 - 3.7
Cleavage: easy
Refractive index: unable to find info
Occurrence: now found in cobalt mines in Morocco.
Crystal or stone size: small, rare
Comments: collector gem, too soft and rare for jewelry.

Rubellite ... see red tourmaline

Ruby ... red corundum

Rutilated quartz ...see rutile and quartz
Rutile...{roo'-teel}...titanium oxide
Comments: synth. is common. A minor ore mineral of titanium, is the most stable of three naturally occurring forms of titanium oxide see OXIDE MINERALS). Rutile forms prismatic or needlelike crystals (tetragonal system), most commonly red-brown in color, streak is pale brown, luster is adamantine to metallic, Widespread in small amounts, rutile occurs in intermediate basic igneous rocks as a high-temperature accessory mineral, in gneiss and schist, and in high-temperature veins and pegmatite dikes. Because it is highly resistant to chemical and physical weathering, it is common in placer deposits.
Safflorite ... see loellingite

Salt...sodium chloride...NaCl...see halite
Comments
Samarium...{suh-mair'-ee-uhm}
Comments
Sanidine ...potassium aluminum silicate...see feldspar
Color: white to gray to yellow
SG: 2.53 - 2.56
Comments: volcanic rock

Sapphire
Satin spar ... see gypsum

Scapolite ...{skap'-oh-lyt}
Crystallography: tetragonal
Colors: pale yellow, colorless, pink chatoyant violet chatoyant
Hardness: 6
Specific gravity: 2.7
Refractive index: avg, 1.57 v. .021
Occurrence: pale yellow from Brazil, chatoyant types are from Burma.
Comments: Scapolite, a member of the feldspathoid group of minerals (sodium and calcium aluminosilicates), consists of a mixture of the minerals marialite and meionite. It occurs in calcium-rich metamorphic rocks, particularly schists, gneisses, and marbles. The name refers to the typical shaftlike shape of the prismatic, white crystals (tetragonal system). Hardness is 5 to 6, luster is vitreous, and specific gravity is 2.5 to 2.8. Some scapolite fluoresces yellow under ultraviolet light.
Scheelite ...{sheel'-yt}
Crystallography: tetragonal
Colors: colorless, yellow, brown, green, white
Luster: adamantine
Hardness: 5
Specific gravity: 6.12
Refractive index: 1.918 - 1.934
Crystal or stone size: massive
Comments: ore of tungsten, collector gem fluoresces strongly light blue under SW UV. Scheelite, calcium tungstate, is an ore mineral of tungsten. It forms pyramidal and tabular crystals (tetragonal system) and columnar or granular masses that vary in color from white through pale yellow. streak is white, luster is glossy, The fact that it fluoresces bright blue white under ultraviolet light enables prospectors to search for it at night, using portable "black" lights. It occurs in veins or pegmatites associated with granite or gneiss, and in contact metamorphic deposits.
Schist...(sp) shist...{shist} a rock
Comments
Schorl... see tourmaline

Scolecite... hydrated calcium aluminum silicate
Crystallography: monoclinic
Colors: colorless, white
Luster: silky
Hardness: 5 - 5.5
Specific gravity: 2.26 - 2.4
Comments: collector item

Scorodite

Selenite ... see gypsum

Sepiolite ... meerschaum
Color: white
SG: 2
Hardness: 2 - 2.5
Comments: used in making pipes

Serpentine...verd...williamsite... bowenite
Crystallography: monoclinic
Colors: yellowish green, green, black, white sometimes dyed
Luster: greasy
Hardness: 2.5 - 4; will.=4; bow.=5 - 5.5
Specific gravity: 2.57; bowenite = 2.8
Refractive index: normal 1.55 - 1.56...extreme 1.49 - 1.57
Crystal or stone size: massive
Comments: used as jade sub. counters, walls The hydrous magnesium silicate mineral serpentine forms from the alteration of olivine and pyroxene in the presence of abundant water. Asbestos, its most fibrous form, is used as an insulating material. Serpentinite, the massive form of serpentine, may be cut and polished for ornamental stone. Serpentinite rocks are found associated with alpine peridotites and ophiolite sequences and are thought to be segments of altered mantle material that have been thrust upward into the Earth's crust.

Siderite ... {sid'-ur-ite}...iron carbonate
Crystallography: hexagonal
Colors:yellow, brown, black
Luster: vitreous
Hardness: 3.5 - 4
Specific gravity: 3.7 - 3.9
Occurrence: The iron carbonate mineral siderite was formerly a major ore. It forms gray-to-brown rhombohedral crystals (hexagonal system) in silver-ore veins, compact concretions called clay ironstone in clay or shale deposits, and impure earthy material stratified with coal deposits called black-band ore. streak is white. Although black-band siderite ore has been mined, the most important ore deposits have been siderite replacements in limestones. good clear crystals are rare.
Comments: crystals are of collector value
Sillimanite...{sil'-uh-muhn-yt}...fibrolite
Crystallography: orthorhombic
Colors: gray, green, white, brown, grayish blue
Hardness: 6 - 7
Specific gravity: 3.24
Refractive index: 1.64 - 1.68
Birefringence: .02
Crystal or stone size: massive
Comments: The aluminum silicate mineral sillimanite, used in the manufacture of spark-plug porcelain and other refractories, has the same chemical formula, as andalusite and kyanite. Also called fibrolite because of its long, needlelike crystals (orthorhombic system) and fibrous masses, sillimanite has a vitreous luster and is brown to grayish. Sillimanite forms by the alteration of mica minerals in clayey sediments. Also an ornamental stone sub. for jade.

Silver...Ag
Color: silver
SG: 10 - 12
Hardness: 2.5 - 3
Comments
Simpsonite ... see microlite

Skutterudite...cobalt arsenide
Color: silverlike
SG: 6.5 - 6.8
Hardness: 6
Comments: cobalt, nickel, and arsenic ore
Smaltite ... skutterudite ... cobalt arsenide
Crystallography: isometric
Colors: gray to black
Luster: metallic
Hardness: 6
Specific gravity: 6.5 - 6.8
Comments: ore of cobalt, nickel, and arsenic
Smithite... see miargyrite

Smithsonite ... zinc carbonate
Crystallography: hexagonal
Colors: white, yellow, light green, blue
Luster: greasy
Hardness: 5
Specific gravity: 4.3
Cleavage: perfect rhombohedral
Refractive index: 1.62 - 1.85
Birefringence: large
Comments: The zinc carbonate mineral smithsonite is an ore of zinc, formed by oxidation of sphalerite. It occurs as rounded, crystalline crusts and granular or honeycombed masses that have a vitreous luster and are typically dirty brown or gray in color, and less often white or of a greenish or bluish hue. Streak is white. It is found with galena and sphalerite in veins and beds, especially in limestone regions.: uniaxial neg. sign.
Soapstone ... see pyrophyllite, talc, steatite
Sodalite ... sodium aluminum silicate chloride
Crystallography: isometric
Colors: blue, white, gray with green tints
Luster: vitreous
Hardness: 5.5 - 6
Specific gravity: 2.27 - 2.33
Cleavage: poor
Refractive index: 1.48
Comments: used as sub. for lapis. Sodalite, a relatively rare sodium aluminosilicate, is one of the feldspathoid minerals. (Lazulite, a blue variety containing sulfur, is the principal component of lapis lazuli.) Sodalite forms dodecahedral crystals, embedded grains, and concentric nodules. Gray, greenish, yellowish, or white in color, it has a vitreous luster. It occurs with other feldspathoids in igneous rocks that have crystallized from sodium-rich magma.

Soddyite... see gummite

Soumansite... see wardite

Spessartite...see garnet... spessartine
Crystallography: cubic
Colors: Red to brown, orange, pink
Hardness: 6.5 - 7.5
Specific gravity: 4.2
Cleavage: none
Refractive index: 1.79 - 1.81
Crystal or stone size: up to 10 cts.
Comments: transparent are cut for gemstones
Sphalerite...{sfal'-ur-yt}...zinc iron sulfide
Crystallography: isometric
Colors: yellow, reddish brown, black (marmatite) pink, green, colorless
Luster: adamantine or resinous some iron rich varieties have submatallic luster
Hardness: 3.5 - 4
Specific gravity: 3.9 - 4.2
Cleavage: perfect
Comments: Sphalerite (ZnS), a common and widely distributed zinc sulfide mineral, is the major ore of zinc. Found in a variety of crystal forms as well as in cleavable, granular, or foliated masses, it ranges from colorless to brown and black in color, darkening as the amount of iron impurities increases. Streak is brownish, luster is resinous to adamantine, Sphalerite, usually in association with the lead sulfide galena, occurs in contact metamorphic deposits, in replacement deposits within limestone and dolomite, and in veins. Much is fluor. in UV
Sphene
Crystallography: monoclinic
Colors: yellow, green, brown
Hardness: 5.5
Specific gravity: 3.53
Refractive index: avg. 1.96 v. .12
Pleochroism: strong
Comments: rare, large DR. dispersion higher than diamond. Sphene, also called titanite, is a titanium and calcium silicate mineral. When transparent and of good color, it is faceted to produce a brilliant, multicolored gem. Sphene forms wedge-shaped crystals (monoclinic system) of various forms and granular masses that range in color from brown to black through gray and green to yellow and red. Hardness is 5 to 5.5, luster is adamantine to resinous, and specific gravity is 3.4 to 3.6. Sphene occurs as an accessory mineral in igneous rocks, notably nepheline syenites, and in gneisses, schists, and marbles.

Spinel...{spuh-nel'}...Ceyonite... gahnosspinel.(shades of blue); Balas Ruby is red spinel, flame, black, purple, yellow, greenish blue
Comments: The magnesium aluminate mineral spinel is used as a GEM when transparent and finely colored. Ruby colored spinel has been confused with RUBY, the Black Prince's Ruby in the British Imperial State Crown being a famous example. The different colors of the mineral, caused by impurities, include various reds, yellow, blue, green, brown, and black, luster is vitreous. Gem spinels occur as crystals and pebbles in placer deposits, where they accumulate because they resist weathering. Common spinel occurs in metamorphic rocks and as an accessory mineral of some basic igneous rocks.

Spodumene
Subtypes: Hiddenite (yellow - green, green);Kunzite (pink-violet, violet)
Crystallography: Monoclinic
Luster: vitreous to glassy
Hardness: 7
Specific gravity: 3.18
Cleavage: easy in two directions
Refractive index: avg. 1.67 v. .015
Pleochroism: distinct
Crystal or stone size: usually long crystals
Comments: true green hiddenite very rare
Staurolite ..{stohr'-uh-lyt} hydrous iron magnesium aluminum silicate .. Greek cross .. St.Andrew's cross
Crystallography: orthorhombic
Colors: gray to black brownish
Luster: vitreous to resinous
Hardness: 7 - 7.5
Specific gravity: 3.73
Occurrence: associated with garnet & kyanite
Comments: The iron and magnesium aluminum silicate mineral staurolite forms well-developed, brown, prismatic crystals Twinned, cruciform pairs, in which one crystal penetrates another, are called fairy crosses and are worn as charms. The crystals often have a rough surface and subvitreous to resinous luster. Staurolite is typical of regional metamorphism, but less so of contact metamorphism. It is often associated with garnet and kyanite in crystalline schists and other altered clay-rich sediments. occurs in 90 & 60 degree angles.

Seatite ... see talc .. soapstone .. pipe stone
Stephanite ... silver antimony sulfide
Crystallography: orthorhombic
Colors: black
Luster: metallic
Hardness: 2 - 2.5
Specific gravity: 6.3
Comments: minor ore of silver

Stibnite ... antimony sulfide
Crystallography: orthorhombic
Colors: gray, red (kermesite), yellow
Luster: metallic iridescent
Hardness: 2
Specific gravity: 4.6 - 4.7
Cleavage: perfect lengthwise
Occurrence: Japan, US, Romania, China world wide
Crystal or stone size: up to 18" long Comments: ore of antimony

Stilbite ... hydrated sodium calcium aluminum silicate
Crystallography: monoclinic
Colors: white, gray, reddish brown
Hardness: 3.5 - 4
Specific gravity: 2.1
Occurrence: US, Scotland, Canada, Brazil
Comments: collector item

Strontianite ... strontium carbonate
Crystallography: orthorhombic
Colors: white, pink, gray, green
Luster: glassy
Hardness: 3.5 - 4
Specific gravity: 3.7
Cleavage: good prismatic
Occurrence: Germany, US, Scotland
Crystal or stone size: compact fibrous masses
Comments: ore of strontium, fireworks, glass

Strontium Titanate ... man made ..strontianite is natural
Crystallography: cubic (man made)
Colors: all, colorless
Hardness: 5.5
Specific gravity: 5.13
Refractive index: 2.41
Crystal or stone size: no more than 2.5 x 10 cm
Comments: mfg. in 50's

Sulphur
Crystallography: orthorhombic
Colors: yellow to brown to black
Hardness: 1
Specific gravity: 2 - 2.1
Cleavage: poor
Occurrence: crystals come from Sicily
Comments: ore, mineral, S, sulfuric acid

Syenite ... igneous rock {sy'-uh-nyt}
Colors: gray, pinkish, violet
Crystal or stone size: massive
Comments: Syenite is a coarse-grained, intrusive igneous rock that is composed largely of sodium- or potassium-rich feldspar and of a ferromagnesian mineral. The feldspar commonly is orthoclase, albite, perthite, or, more rarely, microcline, and the dark-colored ferromagnesian mineral usually is biotite mica, hornblende, or a pyroxene; some examples of syenite also contain feldspathoid minerals. Syenite is in many respects similar to GRANITE; a major difference is the relative lack (less than 5%) or absence of quartz in syenite. Granite is much more commonly found in the field than is syenite.

Sylvanite...{sil'-vuh-nyt} silver gold telluride
Crystallography: monoclinic
Colors: silvery white
Luster: metallic
Hardness: 1.5 - 2
Specific gravity: 8 - 8.3
Cleavage: perfect
Comments: Sylvanite is a rare gold and silver telluride mineral. It forms brilliantly metallic prismatic or tabular crystals (monoclinic system), as well as imperfectly columnar to granular, cleavable masses. Hardness is 1.5 to 2, color and streak are steel gray to silver white, and specific gravity is 8.1. Sylvanite and the other tellurides (calaverite and krennerite) are mined from igneous rocks in the near-surface, low-temperature veins at Cripple Creek, Colo., and in the deeper-seated deposits at Kalgoorlie, Australia.

Sylvite...{sil'-vyt}...potassium chloride
Crystallography: isometric
Colors: colorless, white, blue, yellowish red, purple
Luster: vitreous
Hardness: 2
Specific gravity: 1.99
Comments: fertilizer. The potassium chloride evaporite mineral sylvite (KCl) is mined as a source of potassium. It forms gray, white, or tinted cubic crystals (isometric system) and cleavable granular masses. Luster is vitreous, Sylvite occurs in basinlike bedded salt deposits.
Taaffeite
Crystallography: hexagonal
Colors: pale red violet
Hardness: 8
Specific gravity: 3.61
Refractive index: 1.719 - 1.723
Comments: neg. optic sign, collector gem
Talc ... soapstone .. steatite ... hydrous magnesium silicate
Crystallography: monoclinic
Colors: white, greenish white, gray, brownish
Luster: greasy
Hardness: 1 to 2.5
Specific gravity: 2.58 - 2.83
Refractive index: 1.54 - 1.59
Crystal or stone size: massive
Comments: used for carving, can be cut with knife. Talc is a common, extremely soft, basic magnesium silicate mineral; compact aggregates are known as soapstone (steatite) in reference to their soapy feel. Talc occurs as translucent, foliated or granular masses that vary in color from pale to dark green, with one perfect cleavage. Hardness is 1 (talc is a standard of hardness), streak is white, luster is pearly, and specific gravity is 2.7 to 2.8. Talc crystallizes in the monoclinic system. A low-grade metamorphic mineral, it forms when water and silica or carbon dioxide are added to extensively altered olivine- or pyroxene rich igneous rocks and when water and silica are added to altered carbonate rocks (with the release of carbon dioxide). Talc is also found in crystalline schists. In most instances, talc is found associated with carbonate minerals, particularly dolomite, and is associated frequently with tremolite, forsterite, and serpentine.

Tanzanite... see
zoisite

Tarbuttite ... hydrous zinc phosphate
Color: white, pink, yellow, and green
SG: 4.1
Hardness: 3.7
Comments: collector item

Tetrahedrite - tennantite group .. copper iron sulfide
Color: purplish red or dark blue
SG: 4.5 - 5.2
Hardness: 3 - 4.5
Comments: associated with copper, silver, lead, zinc silver ore.

Thomsonite ... hydrated sodium calcium aluminum silicate
Crystallography: orthorhombic
Hardness: 5 - 5.5
SG: 2.3 - 2.4
RI: 1.515 - 1.54
Colors: white with brown impurities
Crystal or stone size: crystals are rare
Comments: usually cut in cabochon

Thorianite ... thorium uranium oxide
Color: gray to black
SG: 9.7 - 9.8
Hardness: 6.5
Comments: ore of thorium and uranium

Thulite ...see zoisite

Tincalconite ... see borax

Topaz ...an aluminum silicate mineral
Topaz occurs in high-temperature veins, in pegmatites, and in granites and rhyolites, where it is one of the last minerals to form. Luster is vitreous. It has perfect cleavage in one direction. Common topaz is widespread, and fine gem material comes from Saxony, the Ural Mountains, Brazil, Japan, Mexico, and the Cairngorm Mountains in Scotland.

Topazolite... see andradite

Tourmaline ... {tur'-muh-leen}
Subnames: Achroite (colorless); Rubelite (pink to red); Dravite (yellow brown to dark brown; Verelite (green); Indigolite /Indicolite (blue); Siberite (Lilac to violet blue); Schorl (black)

Trachyte...{trak'-yt}
Trachytes are volcanic rocks of intermediate silica and high alkali content. The lava flows from which they originate are usually quite viscous, and consequently they occur as short, thick flows, as tuffs, or as small dikes and sills. Feldspars are the major minerals found in trachytes. Either quartz or feldspathoids, but never both, may also occur, along with alkali-rich mafic minerals such as aegirine, augite, hornblende, and biotite. The lath shaped feldspar crystals are often aligned with the flow direction of the magma, giving rise to the typical trachytic texture. Trachytes are mineralogically and chemically similar to the coarser-grained syenites.
Tremolite ... hydrous calcium magnesium silicate asbestos
Color: white to greenish
SG: 2.9
Hardness: 5 -6
Comments: asbestiform, serpentine, chrysotile forms used as asbestos

Troilite... see pyrrhotite

Troostite... see willemite

Tsavorite ...grossular...see garnet
Colors: green
Occurrence: Kenya
Crystal or stone size: over 1 ct. rare
Comments: collector gem being found more and more in the trade.

Tungstite... tungsten oxide + water... WO3.H2O
Color: yellow earth colors
Crystal system: orthorhombic
Hardness: 2.5
SG: 5.5
Comments: rare

Turnerite... see monazite

Turquoise ...hydrous aluminum phosphate + copper... CuAl6(PO4)4(OH)8.4H2O

Ulexite... hydrous sodium calcium borate... NaCaB5O9.8H2O
Crystal system: triclinic
Color: white
Luster: silky
Hardness: 2.5
SG: 1.6
Comments: desert borax deposits

Uralite ... see
hornblende

Uranium ... Uraninite UO2... uranium dioxide
crystal: cubic
Color: black to gray, greenish
Luster: submetallic to greasy
Hardness: 5 - 6
Comments on Actinide elements
Uranophane... hydrated calcium uranium silicate... CaU2Si2O11.7H2O
Crystal system: rhombic
Color: yellow to orange
Luster: glassy
Hardness: 2 - 3
SG: 3.8 - 3.9
Cleavage: pinacoidal
Comments: fluorescent weak yellow green
Uranotile... see uranophane

Uvarovite ...see garnet... Ca3Cr2Si3O12
Crystal: cubic
Colors: emerald green
Luster: vitreous
Hardness: 6.5 - 7.5
Specific gravity: 3.56 - 4.32
Cleavage: none
Refractive index: 1.81
Occurrence: with olivine and chromite in peridotite of plutonic rocks and in serpentinite of hydrothermal metamorphic rocks.
Comments: collector stone

Vanadinite...{vuh-nay'-duh-nyt} lead vanadate chloride... Pb5(VO4)3Cl
Crystal sys: hexagonal
Color: red to yellow, brown to orange
SG: 6.8 - 7.1
Hardness: 2.75 - 3
Comments: The uncommon lead vanadate mineral vanadinite is an ore of vanadium and a minor source of lead. It forms brown, yellow, or red barrel-shaped prismatic crystals (hexagonal system) in oxidized zones of lead deposits. Streak is white or pale yellow.

Variscite ... hydrated phosphate of aluminum and strengite iron...Utahlite...vermiculite
Crystallography: orthorhombic
Colors:pale green to emerald green, bluish green, green, colorless,
Luster: vitreous, waxy
Hardness: 4 - 4.5
Specific gravity: 2.57
Cleavage: good in one direction
Refractive index: 1.56 - 1.59
Occurrence: West U.S.A. World wide
Crystal or stone size: usually nodules, sometimes confused with turquoise but it has a more green color and is lighter than turq. Comments: The name is from Variscia an ancient district in Germany where the mineral was first found. Crystals are rare but are cut as gemstones for collectors.

Vesuvianite...hydrous calcium magnesium aluminum silicate... Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4
Crystal: ditetragonal
Color: brown, olive green, yellow, red, blue
SG: 3.27 - 3.45
Hardness: 6.5
Comments: crystals ejected by Vesuvius.
Vivianite ... hydrated iron phosphate... Fe3(PO4)2.8H2O
Crystal: monoclinic
Color: blue to greenish black
SG: 2.6 - 2.7
Hardness: 1.5 - 2
Comments: used as a coloring agent

Volborthite ... hydrated copper vanadate
Color: olive green
SG: 3.5 - 3.8
Hardness: 3
Comments: collector item

Wardite... hydrous sodium calcium aluminum phosphate... NaAl3(PO4)2(OH)4.2H2O
Crystal system: tetragonal
Color: bluish green to white
Luster: glassy
Hardness: 5
SG: 2.8 - 2.9
Fracture: conchoidal
Cleavage: good basal
Comments: Named for Henry A. Ward

Wavellite ...{way'-vuh-lyt}... Al3(OH)3(PO4)2.5H2O...hydrous aluminum phosphate
Color: white to green, yellow to brown
SG: 2.4.
Luster: glassy
Hardness:3.25 to 4
Comments: The secondary, hydrated, aluminum phosphate mineral wavellite is widespread in small amounts associated with limonite and phosphate-rock deposits and with low-grade metamorphism. It forms white to green rounded crystalline aggregates. Luster is vitreous to resinous or pearly, streak is white,

Whewellite ... calcium oxalate
Color: white to colorless
SG: 2.23
Hardness: 2.5 (unless you have one, then they are very hard.)
Comments: one of the main components of kidney stones and urinary precipitates
Willemite ... zinc silicate often with manganse and iron... Zn2SiO4
Crystallography: hexagonal
Colors: yellow, green, red, brown, white, colorless.
Luster: resinous to vitreous
Hardness: 5.5
Specific gravity: 3.9 - 4.2
Cleavage: good in three directions
Occurrence: associated w/calcite, franklinite, zincite
Comments: strong fluorescent

Witherite ... barium carbonite... BaCO3
Crystal: orthorhombic
Color: colorless to gray, light yellowish, to white
SG: 4.28
Luster: glassy
Fracture: uneven, brittle
Hardness: 3 - 3.75
Comments: barium ore

Wollastonite... calcium silicate... CaSiO3
Crystal system: triclinic
Color: white to colorless, pink or gray
Luster: glassy to silky
Hardness: 4.5 - 5
SG: 2.8 - 2.9
Fracture: splintery
Cleavage: perfect pinacoidal on base
Comments: often yellow to orange fluorescent used in the mfg. of refractories
Wulfenite {wul'-fen-yt} stolzite, iron manganese tungstate... PbMoO4... wolframite
Crystal sys: tetragonal
Color: reddish brown, blackish brown, yellow
SG: 6.5 -7
Hardness: 2.75 - 3
Comments: ore of tungsten. The lead molybdate mineral wulfenite is a minor ore of lead and molybdenum that occurs in the oxidized zone of lead deposits. It forms brilliant yellow, orange, and reddish, square, tabular crystals (tetragonal system) and granular masses. Streak is white, luster is resinous to adamantine.

Xenotime ... see monazite

YAG ... yttrium aluminum garnet
Crystallography: cubic
Colors: all
Hardness: 8+
Specific gravity: 4.55
Refractive index: 1.83
Crystal or stone size: max. 4 x 20 centimeters
Comments: man made

Zincite...{zink'-yt}...zinc oxide
Crystallography: hexagonal
Colors: deep red to orange, yellow or brown
Hardness: 4
Specific gravity: 5.4 - 5.7
Cleavage: perfect in one direction
Refractive index:
Occurrence: usually found with willemite and franklinite
Comments: ore of zinc tinted with maganese. The zinc oxide mineral zincite (ZnO) is an important zinc ore found at Sterling Hill and Franklin, N.J., although it is rare elsewhere. It forms coarse grains and foliated masses that are orange yellow to deep red in color.
Zircon...{zur'-kahn}

Zoisite


The above is extracted from the GEMSTONE program