geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

and

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the pr ...

, a mineral group is a set of

mineral species In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

with essentially the same crystal structure and composed of chemically similar elements.Stuart J. Mills, Frédéric Hatert, Ernest H. Nickel, and Giovanni Ferraris (2009): "The standardisation of mineral group hierarchies: application to recent nomenclature proposals". ''European Journal of Mineralogy'', volume 21, number 5, pages 1073-1080. Tremolite-chain

For example, the

amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

group consists of 15 or more mineral species, most of them with the general unit formula , where A is a

trivalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

such as or , B is a divalent cation such as , , or , and C is an

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

cation such as , , or . In all these minerals, the anions consist mainly of groups of four tetrahedra connected by shared

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

corners so as to form a double chain of fused six-member rings. In some of the species,

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

may replace some

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

atoms in the backbone, with extra B or C cations to balance the charges.

List of groups

Alunite group Alunite is a hydroxylated aluminium potassium sulfate mineral, formula K Al3( S O4)2(O H)6. It was first observed in the 15th century at Tolfa, near Rome, where it was mined for the manufacture of alum. First called ''aluminilite'' by J.C. De ...

Amphibole group Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is Am ...

* Aragonite group *

Arsenic minerals The arsenic minerals or arsenic group are a group of trigonal symmetry minerals composed of arsenic-like elements, and one alloy. The elements are arsenic, antimony and bismuth Bismuth is a chemical element with the symbol Bi and atomic nu ...

Blodite group The blodite group (or Blödite group) is a group of minerals with two (in most cases divalent) cations and two anions. The group includes blödite Na2Mg(SO4)2•4H2O, leonite Leonite is a hydrated double sulfate of magnesium and potassium. It has ...

Calcite group Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratc ...

Cancrinite group Cancrinite is a complex carbonate and silicate of sodium, calcium and aluminium with the formula Na6 Ca2 O3)2.html" ;"title="carbon">C Coxygen">O3)2">

O3)2">aluminum">Al6silicon.html"_;"title="luminum.html"_;"title="oxygen.html"_;"tit_...

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*_Clay_mineral">Clay_minerals_group_ Clay_is_a_type_of_fine-grained_natural_soil__material_containing_clay_minerals_(hydrous_aluminium_phyllosilicates,_e.g._kaolin,__Al2_Si2_O5(_OH)4). Clays_develop_plasticity_when_wet,_due_to_a_molecular_film_of_water_surrounding_the_clay_parti_...

List of groups

See also

References