Major Mineral Groups (Part 9)
Sulfides
• 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 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)