Minerals

Defining Minerals

  • A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a defined crystalline structure.

Mineral Formation

  • Most minerals are formed through geological processes including cooling and crystallisation of magmas and lavas, and the action of water within a variety of geological environments.
  • Igneous minerals are formed when magma/lava cools and crystallises.
  • Sedimentary minerals form from deposition and lithification of sediments, or precipitation from solutions.
  • Metamorphic minerals form due to changes in temperature, pressure, or the activity of fluids within the crust, altering pre-existing rocks without melting them.

Mineral Identification

  • Minerals can be identified by several physical properties such as colour, streak, lustre, hardness, specific gravity, cleavage, fracture, and crystal habit.

Common Mineral Groups

  • Silicate minerals: These are the most common group, and are based on the silica tetrahedron, a pyramid-shaped combination of silicon and oxygen. Examples: Quartz, Feldspar, Mica.

  • Carbonate minerals: These are commonly found in sedimentary rocks and are based on the CO3 ion. Examples: Calcite, Dolomite.

  • Oxide minerals: Composed of oxygen atoms combined with one or more metallic atoms. Examples: Hematite, Magnetite.

  • Sulphide minerals: Composed of sulphur combined with one or more metals or semimetals. Examples: Pyrite, Galena.

  • Halide minerals: These are formed when halogen elements combine with other elements. Examples: Fluorite, Halite.

Minerals and the Rock Cycle

  • Minerals play a crucial role in the rock cycle. The rock cycle involves the formation, breakdown and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes.
  • All of the rock types — igneous, sedimentary, and metamorphic — can be part of the rock cycle.

Economic Importance of Minerals

  • Minerals hold great economic importance as they are mined for various uses. The uses depend on their inherent physical properties and chemical composition.
  • For instance, minerals are used as gemstones, building materials, or are mined for elements like copper or gold.