A mineral is a naturally occurring, inorganic solid with a definite chemical composition and an ordered, crystalline internal structure.

Basic definition

  • In geology, a mineral is a natural substance, meaning it forms by geological processes rather than being manufactured in a lab.
  • It is inorganic , so it is not produced directly by living organisms or their remains in the way coal or wood are.
  • It is a solid with atoms arranged in a regular, repeating (crystalline) pattern, and it has a specific, or narrowly limited, chemical composition.

Commonly listed criteria

Most introductory geology and mineralogy sources summarize the definition of a mineral with five main criteria:

  1. Naturally occurring (not man‑made under normal definitions).
  2. Inorganic (not formed by life processes, with a few debated exceptions like some biogenic calcite).
  1. Solid at standard Earth surface conditions.
  2. Definite chemical composition (composition is fixed or varies within a small range).
  1. Ordered internal (crystalline) structure, giving characteristic physical properties such as cleavage, hardness, and density.

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