Mineral

Inorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous crystalline 3-dimensional structure. The defined chemical composition can vary between compositional end members within a mineral systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with as observed in the silicateThe most abundant group of minerals in Earth's crust, the structure of silicates are dominated by the silica tetrahedron, SiO44-, with metal ions occurring between tetrahedra). The mesodesmic bonds of the silicon tetrahedron allow extensive polymerization and silicates are classified according to the amount of linking that occurs between the pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category. mineral system. Mineral-like substances that don’t strictly meet the definition (especially if the crystal structureMutual arrangement of atoms, molecules or ions that are packed together in a crystal lattice to form a crystal. is amorphousMaterial without the regular, ordered structure of crystalline solids. Amorphous substances, like glass, lack a definite repeating pattern in their atomic structures (crystallinity). There may be small regions of order, but, overall there is disorder.  ), such as opal and obsidian, are classified as mineraloids. Liquids and gases are not minerals. Substances like coal that are derived from organicPertaining to C-containing compounds. Organic compounds can be formed by both biological and non-biological (abiotic) processes. matter are also not minerals.

However, the definition is not without some interesting examples that provide better insight into the the definition of the word mineral. The following discussion is derived from the article “Is Water a Mineral? Is Ice a Mineral?”

Is Water a Mineral?

If we compare water’s properties to requirements above, we findMeteorite not seen to fall, but recovered at some later date. For example, many finds from Antarctica fell 10,000 to 700,000 years ago. that it fails to qualify as a mineral because water is not a solid and does not have a crystalline structure. However, at temperatures below 32 ^oF or 0 ^oC (at standard atmospheric pressure), water solidifies into ice.

Is Ice a Mineral?

If we compare the properties of ice to the four requirements of the mineral definition, we find that it clearly meets the last three. However, requirement (1) does present a problem. A natural snowflake would be considered to be a mineral because it forms naturally in Earth’s atmosphere. However, an ice cube made in a refrigerator would not be considered a mineral because it was produced by the actions of people.