A mineral is a naturally occurring solid chemical substance formed through biochemical processes, having a characteristic chemical composition, highly ordered atomic structure, and specific physical properties.
By comparison, a rock is an aggregate of minerals and does not have a specific chemical composition.
Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms.
The study of minerals is called mineralogy.
Types of minerals
Types of minerals include the following;
Silicate class
The largest group of minerals by far are the silicates (most rocks are ≥95% silicates), which are composed largely of silicon and oxygen, with the addition of ions such as aluminium, magnesium, iron, and calcium.
Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets, and micas.
Carbonate class
The carbonate minerals consist of those minerals containing the anion (CO3)2− and include calcite and aragonite, dolomite (magnesium/calcium carbonate) and siderite (iron carbonate).
Carbonates are commonly deposited in marine settings when the shells of dead planktonic life settle and accumulate on the seafloor. Carbonates lead to the formation of caves, stalactites, and stalagmites.
The carbonate class also includes nitrate and borate minerals.
Sulfate class
Hank site, Na22K (SO4)9(CO3)2Cl, is one of the few minerals that is considered carbonate and sulfate minerals all contain the sulfate anion, SO4 2−.
Sulfates commonly form in evaporitic settings where highly saline waters slowly evaporate, allowing the formation of both sulfates and halides at the water-sediment interface.
Common sulfates include anhydrite (calcium sulfate), celestine (strontium sulfate), barite (barium sulfate), and gypsum (hydrated calcium sulfate).
The sulfate class also includes the chromate, molybdate, selenate, sulfite, tellurate, and tungstate minerals.
Halide class
The halide minerals are the group of minerals forming the natural salts and include fluorite (calcium fluoride), halite (sodium chloride), sylvite (potassium chloride), and sal ammoniac (ammonium chloride).
Halides, like sulfates, are commonly found in evaporite settings such as salt lakes and landlocked seas such as the Dead Sea and Great Salt Lake.
The halide class includes the fluoride, chloride, bromide and iodide minerals.
Oxide class
Oxide minerals are extremely important in mining as they form many of the ores from which valuable metals can be extracted.
They commonly occur as precipitates close to the Earth’s surface, oxidation products of other minerals in the near-surface weathering zone, and as accessory minerals in igneous rocks of the crust and mantle.
Common oxides include hematite (iron oxide), magnetite (iron oxide), chromite (iron chromium oxide), spinel (magnesium aluminium oxide – a common component of the mantle), ilmenite (iron titanium oxide), rutile (titanium dioxide), and ice (hydrogen oxide).
Sulfide class
Many sulfide minerals are economically important as metal ores. Common sulfides include pyrite, chalcopyrite (copper iron sulfide), pentlandite (nickel iron sulfide), and galena (lead sulfide).
The sulfide class also includes the selenides, the tellurides, the arsenides, the antimonides, the bismuthides, and the sulfosalts (sulfur and a second anion such as arsenic).
Phosphate class
The phosphate mineral group actually includes any mineral with a tetrahedral unit AO4 where A can be phosphorus, antimony, arsenic or vanadium.
By far the most common phosphate is apatite which is an important biological mineral found in teeth and bones of many animals.
The phosphate class includes the phosphate, arsenate, vanadate, and antimonate minerals.
Element class
The elemental group includes native metals and intermetallic elements (gold, silver, copper), semi-metals, and non-metals (antimony, bismuth, graphite, sulfur).
This group also includes natural alloys, such as electrum (a natural alloy of gold and silver), phosphides, silicides, nitrides, and carbides (which are usually only found naturally in a few rare meteorites).
Organic class
The organic mineral class includes biogenic substances in which geological processes have been a part of the genesis or origin of the existing compound.
Minerals of the organic class include various oxalates, mellitates, citrates, cyanates, acetates, formates, hydrocarbons, and other miscellaneous species.
Examples include whewellite, moolooite, mellite, fichtelite, carpathite, evenkite, and abelsonite
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