Minerals are substances that are formed naturally in the Earth.
Minerals are usually solid, inorganic, have a crystal structure, and happen naturally by geological processes.
The study of minerals is called mineralogy.
A mineral can be made of a single chemical element or, more commonly, a compound. There are over 4,000 types of known minerals. Two common minerals are quartz and feldspar.
Characteristics of mineralsEdit
A mineral is a substance that usually;
- is an inorganic solid (elemental mercury is an exception).
- has a definite chemical make-up.
- usually has a crystal structure.
- is formed naturally by geological processes.
One recent definintion is:
"A mineral is a homogeneous naturally occurring substance with a definite but not necessarily fixed chemical composition. Most minerals are solids with an ordered atomic arrangement, and most are inorganic in the chemical sense of that word."
Alternatively, a mineral is one listed as such by the International Mineralogical Association.
Minerals and rocksEdit
Minerals are different from rocks. A mineral is a chemical compound with a given composition and a defined crystal structure. A rock is a mixture of one or several minerals, in varying proportions.
A rock has only two of the characteristics minerals have - it is a solid and it forms naturally. A rock usually contains two or more types of minerals. Two samples of the same type of rock may have different kinds of minerals in them. Minerals are always made up of the same materials in nearly the same proportions. A ruby is a mineral. Therefore, a ruby found in India has similar make-up as a ruby found in Australia.
Formed in natureEdit
Minerals are formed by natural processes. A few substances with the same chemical composition as minerals can be produced by living creatures as part of their shells or bones. The shells of molluscs are composed of either calcite or aragonite, or both.
Traditionally, chemicals produced by living things are not considered minerals. However, it is difficult to see why an organic substance should not be called a mineral if its chemical nature and its crystalline structure is identical with its inorganic twin. This issue is now under depate.