Minerals Topics

Major Mineral Groups (Part 9)


• Sulfide minerals contain sulfur and a metal.

• Common sulfide minerals include: galena and pyrite

Galena Pronounce:

• Galena has a composition of PbS.

• Galena is identified by its metallic, silvery gray luster; gray to dark gray streak; high specific gravity; and three perfect cleavages at 90 degrees.

• Its hardness is 2.5.

• Its specific gravity is 7.4 to 7.6.

• Galena is a lead ore.  It is used in television glass, auto batteries, solder, ammunition, and paint.

Galena is a common lead ore.  Notice how the samples are almost cubes.  Galena is in the cubic crystal system.  The right photograph shows a galena sample and its streak.  Galena’s high specific gravity makes it feel especially heavy.  Its specific gravity helps geologists to identify it. (Photograph by Parvinder Sethi)

Pyrite Pronounce:

• Pyrite has a composition of FeS2.

• Pyrite is identified by its metallic luster; yellow to gold color; and dark gray to black streak.  Cubic crystals are common in pyrite samples.

• Its hardness is 6 to 6.5.

• Its specific gravity is 5.0.

• Pyrite is a sulfur ore.  It is used in sulfuric acid, explosives, fertilizers, pulp processing, and insecticides.

Pyrite, also known as “fool’s gold,” is a sulfide mineral.  It has a lower specific gravity than gold and a black streak.  Real gold has a gold streak. (Photograph by Parvinder Sethi)