What is Beryl?

• Beryl contains the element beryllium.
• It is a ring silicate - the silicate tetrahedra are linked to form rings!
• Beryl commonly grows as elongate crystals with hexagonal cross sections.

See a movie on a beryl structure!

Varieties:

• color: Green
• another example of an emerald, and another another! and another emerald sample.
• emeralds can differ greatly in price and size as a consequence of thier depth and color
• due to presence of Chromium (Cr); pale green due to iron (Fe) impurities that absorb red (transmit green) and fluoresce red
• Comments

• Aquamarine is usually flawless. Next to emerald, it is the most highly prized of the beryls.
• color: pale to medium blue (Latin for sea water); Another example of aquamarine.
• Color is due to presence of iron (Fe) in two oxidation states (ferric and ferrous) and the charge transfer between these ions.
• Heat treatment involves conversion of ferric to ferrous iron.

• color due to presence of Fe-O charge transfer (and rarely, due to uranium)
• rarity and value: rarer than aquamarine, but less valued
• largest gem: 2054 ct (Smithsonian)

• morganite is typically a soft pink / violet, rare peach and salmon
• color due to the presence of manganese (Mn)

• color: red
• due to the presence of manganese (Mn)

• color: colorless
• use: used in eyeglasses

• color: deep blue, fades
• involves irradiation effects and nitrate and carbonate groups in channels in the structure.

Flaws

• crystals of emerald are very brittle
• most emeralds contain flaws:
• inclusions (multiphase inclusions); may reveal geographic location
• another example
• cracks
• many emeralds are oiled, see below
• cutting emerald: the emerald cut
• was developed specifically because emeralds are very prone to cracking when knocked.
• cut with table perpendicular to the length of crystal -> yellowish green
• cut with table parallel to the length of the crystal -> bluish green

• generally far more perfect than emerald
• few cracks or inclusions

Geologic and Geographic origin:

• veins
• hydrothermal and pegmatites
• also found with feldspar and quartz

• Most famous: Colombian - from veins in shales and limestones
• Ancient sources: Egypt (Cleopatra's emerald mines; 2000 B.C.); Austria
• Other: Africa, Pakistan, Brazil, USSR

Synthetics

• Emerald synthesized since 1848 (no facetable gems until 1934)
• generally not economic to synthesize aquamarine etc.
• 3 common methods: (details not required for EPS2 students)
• Catham (since 1940) and Gilson flux method
• Linde hydrothermal method
• Lechteitner hydrothermal overgrowth method.

Make sure you understand the meaning of "hydrothermal"!

Treatments

• heat treatment
• (irradiation)
• most aquamarines in jewelry are heat treated because the natural blue color is pale
• oiling : introduction of oils into fractures that intersect the surfaces of faceted emeralds. This treatment makes the flaws less obvious and enhances the general appearance of the stone.


The treatment or enhancement most commonly encountered is colorless cedar oil. Colorless Canadian balsam, Opticon and other natural and synthetic oils or resins are also in common use. Emeralds treated with these substances are certified as"enhanced or treated".

Using green oil is considered dying. There are certain inferior quality Indian, African, Brazilian, and possibly some Colombian emeralds which do get dyed. It is a fairly common practice with low end beads made in India (information provided by Jeffery Bergman, JLB@thaiphotovoltaics.com).

For the FTC guidelines on treatment disclosure, click here