Galena
This very common ore mineral forms cubes, octahedra, or cubo-octahedral crystals and also occurs in massive, granular, and fibrous habits. Both the color and streak are lead gray. Galena is opaque, with a metallic luster.
FORMATION Galena forms in hydrothermal veins when hot fluids find their way to higher levels in the earth’s crust. It can occur with several other minerals, including fluorite, quartz, calcite, sphalerite, and pyrite.
TESTS This mineral is soluble in hydrochloric acid, producing the “bad eggs” smell of hydrogen sulfide.
Group: SULFIDES
Composition: PbS
Hardness: 2½
SG: 7.58
Cleavage: Perfect cubic
Fracture: Subconchoidal
