Tetrahydrate minerals

Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.

Hydromagnesite is a hydrated magnesium carbonate mineral with the formula .

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.

Phosphophyllite is a rare phosphate mineral with the chemical formula . It is prized among mineral collectors for its delicate bluish green colour, but rarely cut due to its difficult properties.

Blödite or bloedite is a hydrated sodium magnesium sulfate mineral with the formula Na2Mg(SO4)2·4H2O. The mineral is clear to yellow in color often darkened by inclusions and forms monoclinic crystals.

Anapaite is a calcium–iron phosphate mineral with formula: Ca2Fe2+(PO4)2·4H2O. It is a mineral that typically occurs in cavities in fossil bearing sedimentary rocks. It is also found in phosphate bearing iron ores and rarely in pegmatites. It is commonly found with goethite, siderite and vivianite.

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.

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.

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.

Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals.

Ludlamite is a rare phosphate mineral with chemical formula . It was first described in 1877 for an occurrence in Wheal Jane mine in Cornwall, England and named for English mineralogist Henry Ludlam (1824–1880).

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.

Hopeite is a hydrated zinc phosphate with formula: Zn3(PO4)2·4H2O. It is a rare mineral used mainly as a collectors specimen.

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.

Leonite is a hydrated double sulfate of magnesium and potassium. It has the formula K2SO4·MgSO4·4H2O. The mineral was named after Leo Strippelmann, who was director of the salt works at Westeregeln in Germany. The mineral is part of the blodite group of hydrated double sulfate minerals.

Arthurite is a mineral composed of divalent copper and iron ions in combination with trivalent arsenate, phosphate and sulfate ions with hydrogen and oxygen. Initially discovered by Sir Arthur Russell in 1954 at Hingston Down Consols mine in Calstock, Cornwall, England, arthurite is formed as a resultant mineral in the oxidation region of some copper deposits by the variation of enargite or arsenopyrite. The chemical formula of Arthurite is CuFe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O.

Hureaulite is a manganese phosphate with the formula . It was discovered in 1825 and named in 1826 for the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. It is sometimes written as huréaulite, but the IMA does not recommend this for English language text.

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.

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.

Sauconite is a complex phyllosilicate mineral of the smectite clay group, formula Na0.3Zn3(SiAl)4O10(OH)2·4H2O. It forms soft earthy bluish white to red-brown monoclinic crystals typically massive to micaceous in habit. It has a Mohs hardness of 1 to 2 and a specific gravity of 2.45. Optically it is biaxial positive with refractive index values of nα = 1.550 – 1.580, nβ = 1.590 – 1.620 and nγ = 1.590 – 1.620. It is found in vugs and seams in the oxidized zones of zinc and copper deposits. It occurs in association with hemimorphite, smithsonite, chrysocolla, coronadite and various iron oxides.

Santite (KB5O8·4H2O) is a hydrated borate mineral of potassium found in Tuscany, Italy. It is named for Georgi Santi (1746–1823), a former director of the Museum of Natural History, Italy.

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).

Aplowite is a very rare mineral with the formula CoSO4•4H2O, a naturally occurring cobalt(II) sulfate tetrahydrate. It is the lower hydrate when compared to bieberite (heptahydrate) and moorhouseite (hexahydrate), and a higher hydrate when compared to cobaltkieserite (monohydrate). It occurs together with moorhouseite within efflorescences.

Rapidcreekite is a rare mineral with formula Ca2(SO4)(CO3)·4H2O. The mineral is white to colorless and occurs as groupings of acicular (needle-shaped) crystals. It was discovered in 1983 in northern Yukon, Canada, and described in 1986. Rapidcreekite is structurally and compositionally similar to gypsum.

Juansilvaite is a very rare, complex arsenate-sulfate mineral with formula Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O. It is both hydroxyarsenate and dihydroxyarsenate. It is among few relatively new minerals from the Torrecillas mine in Chile, the other being torrecillasite, canutite, chongite, gajardoite, leverettite, and magnesiokoritnigite. Although having quite common among minerals space group C2/c, juansilvaite has a new type of structure.

Changoite is a rare zinc sulfate mineral with the formula Na2Zn(SO4)2·4H2O. Chagoite was discovered in the San Francisco Mine near Sierra Gorda, Antofagasta, Chile. The mineral is a zinc-analogue of blödite, cobaltoblödite, manganoblödite and nickelblödite - other representatives of the blödite group. In terms of chemistry changoite is somewhat similar to gordaite. The mineral's name comes from the Chango people, a group of early inhabitants of northern Chile.

Campigliaite is a copper and manganese sulfate mineral with a chemical formula of Cu4Mn(SO4)2(OH)6·4H2O. It has a chemical formula and also a crystal structure similar to niedermayrite, with Cd(II) cation replacing by Mn(II). The formation of campigliaite is related to the oxidation of sulfide minerals to form sulfate solutions with ilvaite associated with the presence of manganese. Campigliaite is a rare secondary mineral formed when metallic sulfide skarn deposits are oxidized. While there are several related associations, there is no abundant source for this mineral due to its rare process

Malhmoodite is a phosphate mineral first discovered at a mine called Union Carbide in Wilson Springs, Arkansas, United States. This mine is 10 km west of Magnet Cove, an alkaline igneous complex, and Union Carbide is in a contact region of alkalic igneous rocks and surrounding sedimentary rocks. The mineral has been approved by the Commission on New Minerals and Mineral Names, IMA, to be named for the late Bertha K. Malhmood, the Administrative Assistant of the Branch of Analytical Laboratories, U.S. Geological Survey.

Castellaroite is a rare arsenate mineral with formula Mn3(AsO4)2•4H2O. It is related to the phosphate mineral metaswitzerite. Castellaroite is monoclinic, with space group P21/n. The other natural manganese arsenate hydrate is manganohörnesite, which is an octahydrate.

Nickelblödite is a rare nickel sulfate mineral with the formula Na2Ni(SO4)2·4H2O. Nickelblödite was discovered in nickel mines in Carr Boyd Rocks and Kambalda, Western Australia. The mineral is a nickel-analogue of blödite, changoite, cobaltoblödite and manganoblödite - other representatives of the blödite group.

Chaidamuite is a rare zinc – iron sulfate mineral with chemical formula: ZnFe3+(SO4)2(OH)·4H2O.