Minerals: The Building Blocks of Rocks - Geology - page 71

Remembering the Nonsilicate Minerals

While most rock-forming minerals in earth's crust are silicates, the nonsilicate minerals
are important too. Nonsilicate minerals are crystals composed of elements other than
silicon. Composing only about 5 to 8 percent of crustal materials, many of the nonsilic-
ate minerals are found in sedimentary rocks (see Chapter 7) and others are economic-
ally valuable. Here, I describe a few of the major groups of nonsilicate minerals.

Carbonates

Nonsilicate minerals called carbonates are important minerals in sedimentary rocks. The
most common carbonate mineral is calcite, which is the primary mineral in the sedi-
mentary rocks limestone and dolostone and in the metamorphic rock marble. Table 6-2
lists some common carbonate minerals.

Table 6-2 Common Carbonate Minerals

Mineral Name Chemical Formula Common Use

CaCO 3

Calcite Cement

Dolomite CaMg(CO3)2 Cement

Sulfides and sulfates

Nonsilicate minerals made with sulfur include sulfides, such as galena, which provide
useful metals, and sulfates, such as gypsum, which are used in plaster building materials.
These are listed in Table 6-3.

Table 6-3 Sulfide and Sulfate Minerals

Mineral Name Chemical Formula Common Use

Sulfates

Gypsum CaSO4 + 2H20 Plaster

CaSO 4

Anhydrite Plaster

Sulfides

Galena PbS Lead ore