Earth Materials and Structure

Minerals 

A mineral is a naturally occurring inorganic substance with a unique crystal structure. The physical and chemical composition of a mineral is consistent between samples. There are nearly 3000 minerals, only 20 are common, and 10 make up 90% of the minerals of the crust. 

Minerals may be composed of a single element, like gold (Au) or a combination of elements. Minerals composed of more than one element are bound together by electrical bonding. All minerals formed by more than one element are therefore bound together by positive and negative ions. By far the most abundant ions in minerals are the positively charged silicon (Si) and negatively charged oxygen (O). Silicon and oxygen are the foundation of the silicate minerals.

The most important mineral family is the silicates. The silicates are a combination of silicon, oxygen, and another element. Depending on the element, the resulting mineral's density and color can vary considerably. The silicates are subdivided into the ferromagnesian and the nonferromagnesian (or aluminosilicates). Table 14.1 gives examples of other important mineral groups found in the crust.