3.1a Minerals have physical properties determined by their chemical composition and

crystal structure.

¥ Minerals can be identified by well-defined physical and chemical properties, such as

cleavage, fracture, color, density, hardness, streak, luster, crystal shape, and reaction

with acid.

¥ Chemical composition and physical properties determine how minerals are used by


3.1b Minerals are formed inorganically by the process of crystallization as a result ofspecific environmental conditions. These include:

¥ cooling and solidification of magma

¥ precipitation from water caused by such processes as evaporation, chemical reactions,

and temperature changes

¥ rearrangement of atoms in existing minerals subjected to conditions of high

temperature and pressure.

3.1c Rocks are usually composed of one or more minerals.

¥ Rocks are classified by their origin, mineral content, and texture.

¥ Conditions that existed when a rock formed can be inferred from the rock’s mineral

content and texture.

¥ The properties of rocks determine how they are used and also influence land usage by humans.