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mineral

1 Minerals are solid, so do not include liquids and gases. Minerals are solid because the atoms in them are held together in fixed positions by forces called chemical bonds (ssss1).

2 Minerals are naturally occurring, meaning that they occur naturally within the Earth. This definition excludes synthetic solids that are produced only by technologies in laboratories or factories. It does include solid Earth materials that are produced by both natural and synthetic processes, such as natural and synthetic diamonds and the solid materials synthesized in high temperature and high pressure laboratory experiments that are thought to be analogous to real minerals that occur only in the deep interior of Earth.

3 Each mineral species has a specific chemical composition which may vary only within well‐defined limits; that is to say that each mineral possesses a chemical composition that can be expressed by a chemical formula. An example is common table salt or halite which is composed of sodium and chlorine atoms in a 1 : 1 ratio (NaCl). Chemical compositions may vary within well‐defined limits because minerals incorporate impurities, have atoms missing, or otherwise vary from their ideal compositions. In addition some types of atoms may substitute freely for one another when a mineral forms generating a well‐defined range of chemical compositions. For example, magnesium (Mg) and iron (Fe) may substitute freely for one another in the mineral olivine whose composition is expressed as (Mg,Fe)2SiO4. The parentheses are used to indicate the variable amounts of Mg and Fe that may substitute for each other in olivine group minerals (ssss1).