Galena, a lead sulfide, PbS, is the most
important ore mineral of lead. Its metallic, lead gray
cubic crystals (isometric system) and cubic, perfectly
cleavable masses are distinctive and characteristic.
Streak lead gray. Galena is a widespread mineral deposited
by hydrothermal solutions as large, irregular masses in
dolomitized limestones and in zones of contact metamorphism
and as veins in volcanic rocks. It often contains enough
silver to be mined as an ore.