Hexahydrate minerals

Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.

Picromerite (synonyms: schoenite, schönite) is a mineral from the class of hydrous sulfates lacking additional anions, and containing medium to large cations according to the Nickel–Strunz classification.

Ikaite is the mineral name for the hexahydrate of calcium carbonate, . Ikaite tends to form very steep or spiky pyramidal crystals, often radially arranged, of varied sizes from thumbnail size aggregates to gigantic salient spurs. It is only found in a metastable state and decomposes rapidly by losing most of its water content once removed from near-freezing water. This "melting mineral" is more commonly known through its pseudomorphs.

Andersonite, Na2Ca(UO2)(CO3)3·6H2O, or hydrated sodium calcium uranyl carbonate is a rare uranium carbonate mineral that was first described in 1948. Named after Charles Alfred Anderson (1902–1990) of the United States Geological Survey, who first described the mineral species, it is found in sandstone-hosted uranium deposits. It has a high vitreous to pearly luster and is fluorescent. Andersonite specimens will usually glow a bright lemon yellow (or green with blue hints depending on the deposit) in ultraviolet light. It is commonly found as translucent small rhombohedral crystals that have a

thumb | right | alt=boussingaultite | boussingaultite Boussingaultite is a rare ammonium magnesium hydrated sulfate mineral of the chemical formula: (NH4)2Mg(SO4)2 · 6 H2O. The formula of boussingaultite is that of Tutton's salts type. It was originally described from geothermal fields in Tuscany, Italy, where it occurs together with its iron analogue mohrite, but is more commonly found on burning coal dumps. The mineral possess monoclinic symmetry and forms clear, often rounded crystals.

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.

Yingjiangite is a mineral named after its type locality in the Yingjiang county in 1990. It is a member of the phosphuranylite group.

Atencioite is a calcium iron phosphate mineral with the chemical formula CaFeMgBe(PO)(OH)·6HO. Its type locality is Divino das Laranjeiras, Minas Gerais, Brazil. It was named after Daniel Atencio, a mineralogy professor at the University of São Paulo.

Zincoberaunite is an iron and zinc phosphate mineral, the Zn analogue of beraunite. It was first described by Chukanov et al. for an occurrence in Hagendorf Sud pegmatite in Germany. Zincoberaunite occurs as a secondary mineral as an alteration product of primary phosphate minerals in granite pegmatites.

Metavivianite () is a hydrated iron phosphate mineral found in a number of geological environments. As a secondary mineral it is typically formed from oxidizing vivianite. Metavivianite is typically found as dark blue or dark green prismatic to flattened crystals.