Mineralogy, as the name suggests, is the study of minerals. There are several definitions of "mineral," depending on how they are studied. Chemists would define minerals as particular chemical elements or compounds. Dietitians would define a mineral as a substance that is required in the diet for good nutrition, for example, calcium, potassium, and magnesium. Sometimes all of matter on the Earth is classified as either animal, vegetable, or mineral, which would suggest that all inorganic substances are minerals. This is incorrect, although all minerals are inorganic substances. Rocks in the Earth's crust are composed of one or more minerals. A mineral in the geologic sense is a naturally occurring, inorganic, crystalline solid. A particular mineral has a specific chemical composition. Each mineral has its own physical properties such as color, hardness, and density.

Most minerals are chemical compounds that are made of two or more different elements...