Hydroxide minerals

thumb|upright|Unusual specimen of goethite replacing a gypsum [[stalactite; the center is hollow. From Santa Eulalia, Chihuahua, Mexico.]] Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α-polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszu

Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is an intermediate mineral with formula CuZn(AsO4)(OH). Mang

thumb|right|Ball-and-stick model of the part of the [[crystal structure of gibbsite]] Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al(OH)3 (but sometimes as α-Al(OH)3). It is also sometimes called hydrargillite (or hydrargyllite).

Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and the luster brilliant and submetallic. The streak is dark reddish brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces. Twinned crystals are not infrequent.

Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described from deposits in the Atacama Desert of Chile in 1802 by Dmitri Alekseyevich Golitsyn. The Atacama Desert is also the namesake of the mineral.

Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites. Brucite is often found in association with serpentine, calcite, aragonite, dolomite, magnesite, hydromagnesite, artinite, talc and chrysotile.

Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite. It is dimorphous with diaspore. It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit. It is white with tints of yellow, green, brown or red due to impurities. It has a vitreous to pearly luster, a Mohs hardness of 3 to 3.5 and a specific gravity of 3.00 to 3.07. It is colorless in thin section, optically biaxial positive with refractive indices of nα = 1.644 – 1.648, nβ = 1.654 – 1.657 and nγ = 1.661 – 1.668.

Diaspore ()also called diasporite, empholite, kayserite, or tanatariteis an aluminium hydroxide oxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect clea

Axinite is a brown to violet-brown, or reddish-brown bladed group of minerals composed of calcium aluminium boro-silicate, . Axinite is pyroelectric and piezoelectric.

Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when iron-containing substances rust underwater. Lepidocrocite is commonly found in the weathering of primary iron minerals and in iron ore deposits. It can be seen as rust scale inside old steel water pipes and water tanks.

Wavellite is an aluminium basic phosphate mineral with formula Al3(PO4)2(OH, F)3·5H2O. Distinct crystals are rare, and it normally occurs as translucent green radial or spherical clusters.

Brazilianite, whose name derives from its country of origin, Brazil, is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites.

The rare mineral adelite, is a calcium, magnesium, arsenate with chemical formula CaMgAsO4OH. It forms a solid solution series with the vanadium-bearing mineral gottlobite. Various transition metals substitute for magnesium and lead replaces calcium leading to a variety of similar minerals in the adelite–duftite group.

Hydromagnesite is a hydrated magnesium carbonate mineral with the formula .

Abhurite is a mineral of tin, oxygen, hydrogen, and chlorine with the formula Sn21O6(OH)14Cl16 or Sn3O(OH)2Cl2. It is named after its type locality, a shipwreck with tin ingots at Sharm Abhur, a cove near Jeddah in the Red Sea. Abhurite forms alongside other tin minerals like romarchite and cassiterite. Abhurite can vary in color, from pale green/yellow to darker brown/green.

Artinite is a hydrated basic magnesium carbonate mineral with formula: . It forms white silky monoclinic prismatic crystals that are often in radial arrays or encrustations. It has a Mohs hardness of 2.5 and a specific gravity of 2.

Hydrotalcite, or formerly also völknerite, is a layered double hydroxide (LDH) of general formula , whose name is derived from its resemblance with talc and its high water content. Multiple structures containing loosely bound carbonate () ions exist. The easily exchangeable carbonates enable applications of the mineral in wastewater treatment and the immobilisation of radioactive waste after nuclear fuel reprocessing.

thumb|Putnisite (animation) Putnisite is a mineral composed of strontium, calcium, chromium, sulfur, carbon, oxygen and hydrogen. It was discovered on the Polar Bear Peninsula in Shire of Dundas, Western Australia in 2007 during mining activity. Following identification and recognition by the IMA in 2012 the mineral was named after mineralogists Andrew and Christine Putnis. The formal description was published in 2014.

Aheylite is a rare phosphate mineral with formula (Fe2+Zn)Al6[(OH)4|(PO4)2]2·4(H2O). It occurs as pale blue to pale green triclinic crystal masses. Aheylite was made the newest member of the turquoise group in 1984 by International Mineralogical Association Commission on New Minerals and Mineral Names.

Portlandite is a hydroxide-bearing mineral typically included in the oxide mineral class. It is the naturally occurring form of calcium hydroxide (Ca(OH)2) and the calcium analogue of brucite (Mg(OH)2).

Serandite is a mineral with formula Na(Mn2+,Ca)2Si3O8(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.

Bentorite is a mineral with the chemical formula . It is colored violet to light violet. Its crystals are hexagonal to dihexagonal dipyramidal. It is transparent and has vitreous luster. It has perfect cleavage. It is not radioactive. Bentorite is rated 2 on the Mohs scale.

Allactite is a rare arsenate mineral of metamorphosed manganese zinc ore deposits. It is found in Sweden and New Jersey, US. Its name originated from the Greek αλλάκτειν (allaktein) meaning "to change", referring to the strong pleochroism of the mineral.

Lindgrenite is an uncommon copper molybdate mineral with formula: Cu3(MoO4)2(OH)2. It occurs as tabular to platey monoclinic green to yellow green crystals.

Beraunite is an iron phosphate mineral. It was first described by August Breithaupt for an occurrence in Beraun currently in the Czech Republic. Beraunite occurs as a secondary mineral in iron ore deposits, and as an alteration product of primary phosphate minerals in granite pegmatites.

Zaratite is a bright emerald green nickel carbonate mineral with formula Ni3CO3(OH)4·4H2O. Zaratite crystallizes in the isometric crystal system as massive to mammillary encrustations and vein fillings. It has a specific gravity of 2.6 and a Mohs hardness of 3 to 3.5. It has no cleavage and is brittle to conchoidal fracture. The luster is vitreous to greasy.

Edenite or edenitic hornblende is a double chain silicate mineral of the amphibole group with the general chemical composition NaCa2Mg5(Si7Al)O22(OH)2. Edenite is named for the locality of Edenville, Orange County, New York, where it was first described.

Akrochordite is a rare hydrated arsenate mineral with the chemical formula and represents a small group of rare manganese (Mn) arsenates and, similarly to most other Mn-bearing arsenates, possess pinkish colour. It is typically associated with metamorphic Mn deposits.

Clarkeite is a uranium oxide mineral with the chemical formula or .

Diaboleite is a blue-colored mineral with formula Pb2CuCl2(OH)4. It was discovered in England in 1923 and named diaboleite, from the Greek word διά and boleite, meaning "distinct from boleite". The mineral has since been found in a number of countries.

Inyoite, named after Inyo County, California, where it was discovered in 1914, is a colourless monoclinic mineral. It turns white on dehydration. Its chemical formula is Ca(HBO)(OH)·4HO or CaB3O3(OH)5·4H2O. Associated minerals include priceite, meyerhofferite, colemanite, hydroboracite, ulexite and gypsum.

Asbolane, previously cobalt ochre is a manganese (IV) oxy-hydroxide mineral containing also cobalt, nickel, magnesium, and calcium ions. It crystallizes in the hexagonal crystal system. Its chemical formula is .

Birnessite (nominally MnO2·nH2O), also known as δ-, is a hydrous manganese dioxide mineral with a chemical formula of Na0.7Ca0.3Mn7O14·2.8H2O. It is the main manganese mineral species at the Earth's surface, and commonly occurs as fine-grained, poorly crystallized aggregates in soils, sediments, grain and rock coatings (e.g., desert varnish), and marine ferromanganese nodules and crusts. It was discovered at Birness, Aberdeenshire, Scotland.

Alleghanyite is a moderately rare humite mineral with formula Mn5(SiO4)2(OH)2, belonging to the nesosilicates class. In general its occurrences are related with metamorphic (metamorphosed) manganese deposits. The mineral is named after Alleghany County, North Carolina, US.

Tokyoite is a rare barium manganese vanadate mineral with the chemical formula: Ba2(Mn3+,Fe3+)OH(VO4)2. It is the manganese analogue of the iron rich gamagarite and the barium analogue of the lead vanadate, brackebuschite.

Diadochite is a phospho-sulfate mineral. It is a secondary mineral formed by the weathering and hydration of other minerals. Its formula is Fe2(PO4)(SO4)OH·5H2O. Well crystallized forms are referred to as destinezite, which has been given official recognition by the International Mineralogical Association with diadochite being the poorly formed to amorphous variety.

Strashimirite (IMA symbol: Ssh) is a rare monoclinic mineral containing arsenic, copper, hydrogen, and oxygen. It has the chemical formula .

Xocomecatlite is a rare tellurate mineral with formula: Cu3(TeO4)(OH)4. It is an orthorhombic mineral which occurs as aggregates or spherules of green needlelike crystals.

thumb|alt=X-ray diffraction patterns for six-line and two-line ferrihydrite.|X-ray diffraction patterns for six-line (top) and two-line (bottom) ferrihydrite. Cu Kα radiation.

Feroxyhyte is an oxide/hydroxide of iron, δ-Fe3+O(OH). Feroxyhyte crystallizes in the hexagonal system. Feroxyhyte forms as brown, rounded to concretionary masses. Feroxyhyte is an opaque, magnetic mineral with a yellow streak and a relative density of 4.2.

Manganvesuvianite is a rare mineral with formula . The mineral is red to nearly black in color. Discovered in South Africa and described in 2002, it was so named for the prevalence of manganese in its composition and its relation to vesuvianite.

Stichtite is a mineral, a carbonate of chromium and magnesium; formula Mg6Cr2CO3(OH)16·4H2O. Its colour ranges from pink through lilac to a rich purple colour. It is formed as an alteration product of chromite-containing serpentine. It occurs in association with barbertonite (the hexagonal polymorph of Mg6Cr2CO3(OH)16·4H2O), chromite and antigorite.

Tarbuttite is a rare phosphate mineral with formula Zn2(PO4)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Coventry Tarbutt.

porous secondary manganese oxides, mainly

Arhbarite (IMA symbol: Arh) is a copper magnesium arsenate mineral with the chemical formula CuMg(AsO)(OH). It is named after its type locality, the Arhbar mine in Ouarzazate Province in Drâa-Tafilalet, Morocco.

Sturmanite is a rare sulfate mineral with the chemical formula Ca6Fe3+2(SO4)2.5(B(OH)4)(OH)12 · 25 H2O. It crystallises in the tetragonal system and it has a Moh's hardness of 2.5. Sturmanite has a bright yellow to amber colour and falls in the ettringite group. It was named after Bozidar Darko Sturman (born 1937), Croatian-Canadian mineralogist and Curator Emeritus of Mineralogy, Royal Ontario Museum.

Derriksite is a very rare uranium mineral with the chemical formula Cu4(UO2)(SeO3)2(OH)6•H2O. It is a secondary mineral that contains copper, uranium and the rarer selenium. It is a bright green to duller bottle green colour. Its crystal habit is acicular, it is most likely to be found along with the uranyl selenium mineral demesmaekerite, but derriksite is much rarer than demesmaekerite. It is named after Jean Marie Francois Joseph Derriks (1912–1992), geologist and administrator of the Union Minière du Haut Katanga (UMHK). It has a Mohs hardness of about 2.

Marthozite is an orthorhombic mineral that has a general formula of Cu(UO2)3(SeO3)3(OH)2·7H2O. It was named after Belgian mineralogist Aimé Marthoz (1894–1962), former Director-general of the Union Minière du Haut Katanga (UMHK).

Niedermayrite is a rare hydrated copper cadmium sulfate hydroxide mineral with formula: Cu4Cd(SO4)2(OH)6·4H2O. It crystallizes in the monoclinic system and occurs as encrustations and well formed vitreous blue-green prismatic crystals. It has a specific gravity of 3.36.

Fougèrite is a relatively recently described naturally occurring green rust mineral. It is the archetype of the fougèrite group in the larger hydrotalcite supergroup of naturally occurring layered double hydroxides. The structure is based on brucite-like layers containing Fe2+ and Fe3+ cations, O2− and OH− anions, with loosely bound [CO3]2− groups and H2O molecules between the layers. Fougèrite crystallizes in trigonal system. The ideal formula for fougèrite is [Fe2+4Fe3+2(OH)12][CO3]·3H2O. Higher degrees of oxidation produce the other members of the fougèrite group, namely trébeurdenite, [Fe2

Cumengeite, also known as cumengite, is a secondary mineral that was named after mining engineer Bernard Louis Philippe Édouard Cumenge, who found the first specimens. It is easily confused with diaboleite. It is a valid species that was first described prior to 1959, and is grandfathered now, but it has been a valid species since 1893, since pre-IMA. It is the hydroxychloride of lead and copper.

Herbertsmithite is a rhombohedral green-coloured mineral with chemical formula ZnCu3(OH)6Cl2. It is named after the mineralogist Herbert Smith (1872–1953) and was first found in 1972 in Chile. It is polymorphous with kapellasite and closely related to paratacamite. Herbertsmithite has also been found near Anarak, Iran, hence its other name, anarakite.

Sonolite is a mineral with formula Mn9(SiO4)4(OH,F)2. The mineral was discovered in 1960 in the Sono mine in Kyoto Prefecture, Japan. In 1963, it was identified as a new mineral and named after the Sono mine.

Joaquinite-(Ce) is a rare silicate mineral with the chemical formula NaBa2Ce2Fe2+Ti2Si8O26(OH)·2H2O. It crystallizes in the monoclinic system with orthorhombic pseudomorphism and exhibits tabular crystals.

Atelestite is an arsenate mineral with the chemical formula Bi(AsO)O(OH). Its type locality is Erzgebirgskreis, Saxony, Germany.

Cadwaladerite is a rare aluminium halide mineral with formula: AlCl(OH)2·4(H2O). It was reported for an amorphous substance associated with sulfate minerals and embedded in a halite crystal cluster. Its status is uncertain due to inadequate data. It was first described in 1941 for an occurrence in mine dumps of the Victoria Segunda mine Cerros Pintados, Iquique province, Tarapacá Region, Chile. It was named for Charles Meigs Biddle Cadwalader, president of the Academy of Natural Sciences. Lesukite was discredited (IMA2018-H).

Gottlobite, ), is a mineral in the adelite group found as isolated crystals or isometric grains of orange or orange-brown color. The size of the crystals are a half millimeter in diameter and are part of the orthorhombic crystal system. Gottlobite is the vanadate end member in a solid solution formed with adelite (). Gottlobite is also part of the vanadates and arsenates group. With these characteristics, it is similar to the minerals tangeite and austinite by X-ray diffraction methods.

Felsőbányaite or basaluminite is a hydrated aluminium sulfate mineral with formula: Al4(SO4)(OH)10·4H2O. It is a rare white to pale yellow mineral which typically occurs as globular masses and incrustations or as minute rhombic crystals. It crystallizes in the monoclinic crystal system.

Astrocyanite-(Ce) is a bright blue mineral with the chemical formula . Its type locality is Kamoto East Open Cut, Kamoto, Kolwezi, Lualaba, Congo