Antimony from California, USA. (public display, South Dakota School of Mines and Technology Museum of Geology, Rapid City, South Dakota, USA)

A mineral is a naturally-occurring, solid, inorganic, crystalline substrance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals.

To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals.

The semimetal/metalloid antimony (Sb) is not common in its native state. It has a metallic luster, silvery-gray color, is somewhat soft (H=3 to 3.5), and is moderately heavy for its size. Other semimetals that occur as native elements are arsenic (As) and bismuth (Bi). The semimetals/metalloids resemble metals in luster, but they break along fractures - they’re brittle. True metals are malleable.