Minerals – PP. 30-32

1. Minerals – PP. 30-32 *Practically every manufactured product contains materials obtained from minerals. *A basic knowledge of Earth materials is essential to an understanding of all geologic phenomena. *Earth materials that are classified as minerals exhibit the following characteristics: naturally occuring, solid, orderly crystalline structure, well-defined chemical composition, and generally inorganic. *The term aggregate implies that the minerals are joined in such a way that the properties of each mineral are retained. * A few rocks are composed of nonmineral matter. These include the volcanic rocks obsidian, pumice, and coal.

2. Minerals pp. 35-40 • 1. The more easily recognized physical properties are frequently used in identification. • 2. The primary physical properties that are commonly used to identify hand samples are luster, color, streak, crystal shape, tenacity, hardness, cleavage, fracture, and density, or specific gravity. • 3. Ionicallybonded minerals tend to be brittle. • 4. Minerals with metallic bonds are easily hammered into place. They are malleable. • 5. Minerals that can be cut into thin shavings are described as sectile.

3. 6. Minerals are elastic and will bend and snap back to their original shape. 7. Do not confuse cleavage with crystal shape. 8. When minerals fracture, most produce uneven surfaces and are described as exhibiting irregular fracture. 9. Some minerals break into smooth, curved surfaces and are called conchoidal fractures. 10. Minerals that exhibit fractures that produce splinters or fibers are referred to as splintery and fibrous fracture. 11. Most common rock-forming minerals have a specific gravity between 2 and 3. 12. When a transparent piece of calcite is placed over printed material, the letters appear twice and are known as double refraction.