Minerals in space group 227

thumb|upright=1.25|Main diamond producing countries

thumb|Polyhedral representation of spinel MgAl2O4 Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of spine, in reference to its pointed crystals.

Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (MgCr2O4). Substitution of the element aluminium can also occur, leading to hercynite (FeAl2O4). Chromite today is mined particularly to make stainless steel through the production of ferrochrome (FeCr), which is an iron-chromium alloy.

Cristobalite ( ) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, which also include coesite, tridymite and stishovite. It is named after Cerro San Cristóbal in Pachuca Municipality, Hidalgo, Mexico.

Arsenolite is an arsenic mineral, with chemical formula As2O3. It is formed as an oxidation product of arsenic sulfides. Commonly found as small octahedra, it is white, but impurities of realgar or orpiment may give it a pink or yellow hue. It can be associated with its dimorph claudetite (a monoclinic form of As2O3) as well as realgar (As4S4), orpiment (As2S3) and erythrite, Co3(AsO4)2·8H2O.

Gahnite, ZnAl2O4, is a rare mineral belonging to the spinel group. It forms octahedral crystals which may be green, blue, yellow, brown or grey. It often forms as an alteration product of sphalerite in altered massive sulphide deposits such as at Broken Hill, Australia. Other occurrences include Falun, Sweden where it is found in pegmatites and skarns; and, in the United States, Charlemont, Massachusetts; Spruce Pine, North Carolina; White Picacho district, Arizona; Topsham, Maine; and Franklin, New Jersey.

Pyrochlore () is a mineral group of the niobium end member of the pyrochlore supergroup. Pyrochlore is also a term for the crystal structure Fdm. The name is from the Greek , fire, and , green because it typically turns green on ignition in classic blowpipe analysis.

thumb|Scanning electron microscope|SEM image of Ringwoodite (RGW) discovered in the Suizhou L6 [[chondrite meteorite. See image for details. ]]

Franklinite is an oxide mineral belonging to the normal spinel subgroup's iron (Fe) series, with the formula ZnFe3+2O4.

Jacobsite is a manganese iron oxide mineral. It is in the spinel group and forms a solid solution series with magnetite. The chemical formula is (Mn,Mg)Fe2O4 or with oxidation states and substitutions: (Mn2+,Fe2+,Mg)(Fe3+,Mn3+)2O4. thumb|left|Jacobsite, N'Chwaning Mines, Kuruman, Kalahari manganese fields, [[Northern Cape Province, South Africa. Size 3.8 x 3.5 x 3.2 cm]]

Villiaumite is a rare halide mineral composed of sodium fluoride, NaF. It is very soluble in water and some specimens fluoresce under long and short wave ultraviolet light. It has a Mohs hardness of 2.5 and is usually red, pink, or orange in color. It is toxic to humans.

Greigite is an iron sulfide mineral with the chemical formula . It is the sulfur equivalent of the iron oxide magnetite (Fe3O4). It was first described in 1964 for an occurrence in San Bernardino County, California, and named after the mineralogist and physical chemist Joseph W. Greig (1895–1977).

thumb|Betafite, Gunnison, Colorado

Microlite was once known as a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine. Its chemical formula is . Today it is a name of a group of oxide minerals of a similar stoichiometry having tantalum prevailing over titanium and niobium. The microlite group belongs to a large pyrochlore supergroup that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals wi

Trevorite is a rare nickel iron oxide mineral belonging to the spinel group. It has the chemical formula NiFe3+2O4. It is a black mineral with the typical spinel properties of crystallising in the cubic system, black streaked, infusible and insoluble in most acids.

Linnaeite is a cobalt sulfide mineral with the composition Co+2Co+32S4. It was discovered in 1845 in Västmanland, Sweden, and was named to honor Carl Linnaeus (1707–1778).

Hercynite is a spinel mineral with the formula FeAl2O4.

Stibiconite, also formerly known as stiblite or antimony ochre is an antimony oxide mineral with formula: Sb3O6(OH). Its name originates from Greek (), 'antimony' and (), 'powder', alluding to its composition and habit. It is a member of the pyrochlore super group.

Ulvöspinel or ulvite is an iron titanium oxide mineral with formula: Fe2TiO4 or TiFe2+2O4. It forms brown to black metallic isometric crystals with a Mohs hardness of 5.5 to 6. It belongs to the spinel group of minerals, as does magnetite, Fe3O4.

Galaxite, also known as 'mangan-spinel' is an isometric mineral belonging to the spinel group of oxides with the ideal chemical formula . It is sometimes used as a gemstone.

Magnesioferrite is a magnesium iron oxide mineral, a member of the magnetite series of spinels. Magnesioferrite crystallizes as black metallic octahedral crystals. It is named after its chemical composition of magnesium and ferric iron. The density is 4.6 - 4.7 (average = 4.65), and the diaphaniety is opaque. Occurs as well-formed fine sized crystals or massive and granular. Its hardness is 6-6.5. It has a metallic luster and a dark red streak.

Faujasite (FAU-type zeolite) is a mineral group in the zeolite family of silicate minerals. The group consists of faujasite-Na, faujasite-Mg and faujasite-Ca. They all share the same basic formula by varying the amounts of sodium, magnesium and calcium. Faujasite occurs as a rare mineral in several locations worldwide.

Carrollite, CuCo2S4, is a sulfide of copper and cobalt, often with substantial substitution of nickel for the metal ions, and a member of the linnaeite group. It is named after the type locality in Carroll County, Maryland, US, at the Patapsco mine, Sykesville.

Siegenite (also called grimmite, or nickel cobalt sulfide) is a ternary transition metal dichalcogenide compound with the chemical formula (Ni,Co)3S4. It has been actively studied as a promising material system for electrodes in electrochemical energy applications due to its better conductivity, greater mechanical and thermal stability, and higher performance compared to metal oxides currently in use. Potential applications of this material system include supercapacitors, batteries, electrocatalysis, dye-sensitized solar cells, photocatalysis, glucose sensors, and microwave absorption.

Indite is an extremely rare indium-iron sulfide mineral, found in Siberia. Its chemical formula is FeIn2S4.

Violarite (Fe2+Ni23+S4) is a supergene sulfide mineral associated with the weathering and oxidation of primary pentlandite nickel sulfide ore minerals.

cubic crystal structure of diamond and other substances

REDIRECT Antimony trioxide

Cadmoindite (CdIn2S4) is a rare cadmium indium sulfide mineral discovered in Siberia around the vent of a high-temperature (450–600 °C) fumarole at the Kudriavy volcano, Iturup Island in the Kuril Islands. It has also been reported from the Kateřina Coal Mine in Bohemia, Czech Republic.

Kalininite (ZnCr2S4) is a thiospinel mineral found in Russia in 1985 in the Pereval Marble Quarry, Slyudyanka (Sludyanka), Lake Baikal area, Irkutskaya Oblast', Prebaikalia (Pribaikal'e), Eastern-Siberian Region. It was named for P. V. Kalinin, Russian mineralogist and petrologist, investigator of the southern Baikal region.

Polydymite, Ni2+Ni23+S4, is a supergene thiospinel sulfide mineral associated with the weathering of primary pentlandite nickel sulfide.

Zincochromite is a zinc chromium oxide mineral with the formula ZnCr2O4. It is the zinc analogue of chromite, hence the name. It was first described in 1987 as an occurrence in a uranium deposit near Lake Onega, Russia. It has also been reported from Dolo Hill, New South Wales, Australia, and from the Tarkwa Mine in the Ashanti gold belt of Ghana.

Tyrrellite is a selenide mineral that has a chemical formula of . It has been found in the Goldfields District in northern Saskatchewan, as well as in the Petrovice deposit, Czech Republic. It is named after the Canadian geologist Joseph Burr Tyrrell. Joseph Tyrrell was one of the first geologists from the Geological Survey of Canada to do research in the Goldfields District.

Daubréelite is a rare sulfide mineral. It crystallizes with cubic symmetry and has chemical composition of Fe2+Cr3+2S4. It usually occurs as black platy aggregates.

Filipstadite is a very rare mineral of the spinel group, with the formula . It is isometric, although it was previously thought to be orthorhombic. When compared to a typical spinel, both the octahedral and tetrahedral sites are split due to cation ordering. Filipstadite is chemically close to melanostibite. The mineral comes from Långban, Sweden, a manganese skarn deposit famous for many rare minerals.

Xingzhongite is an opaque, metallic mineral named for its location of discovery in China.

Fletcherite is a rare thiospinel sulfide mineral with formula . It is an opaque metallic steel gray mineral which crystallizes in the cubic crystal system. It is a member of the linnaeite group.

Hydrokenoelsmoreite is a hydrous tungsten oxide mineral with formula □2W2O6(H2O). Hydrokenoelsmoreite is a colorless to white, translucent isometric mineral. It has a Mohs hardness of 3, exhibits no cleavage and has a splintery fracture. It has a vitreous to adamantine luster. It is optically isotropic with an index of refraction of n = 2.24.

Nichromite is a black cubic metallic mineral and member of the spinel group. Nichromite was originally reported from the Bon Accord nickel deposit in Barberton District, South Africa. Occurring naturally in a nickel deposit, nichromite is named for chromite with dominant nickel.

Joegoldsteinite is a rare sulfide mineral with the formula MnCr2S4. It was discovered in Social Circle meteorite found in Georgia, US. The mineral is named after Joseph (Joe) I. Goldstein.