Major Mineral Groups (Part 8)
Sulfates
• Sulfate minerals contain sulfur and oxygen (SO4) combined with other elements.
• Common sulfate minerals include: gypsum and barite.
Gypsum Pronounce:
• Gypsum has a composition of CaSO4·nH2O.
• Gypsum is identified by its non-metallic luster; colorless to white color; and very low hardness.
• Gypsum is soft. Its hardness is 2.
• Its specific gravity is 2.3.
• Gypsum is used in wallboard (drywall) and plaster of paris.
Gypsum, shown here, is a sulfate mineral. This variety of gypsum, characterized by long, shiny needles, is called satinspar. (Photograph by Parvinder Sethi)
• Barite has a composition of BaSO4.
• Barite is identified by its high specific gravity; white or light color; and white streak.
• Barite is identified by its high specific gravity; white or light color; and white streak.
• Its hardness is 3 to 3.5.
• Its specific gravity is 4.5.
• Barite is used in paint, drilling muds, and in paper and textiles.
Barite is another sulfate mineral. It has an unusually high specific gravity for a light-colored mineral. Its high specific gravity makes it useful as an additive to drilling muds that help keep oil and gas wells from blowing out. (Photograph by Stan Johnson)