Oxalate minerals

Whewellite is a mineral, hydrated calcium oxalate, formula Ca C2O4·H2O. Because of its organic content it is thought to have an indirect biological origin; this hypothesis is supported by its presence in coal and sedimentary nodules. However, it has also been found in hydrothermal deposits where a biological source appears improbable. For this reason, it may be classed as a true mineral.

thumb|Raphides in Epipremnum ''Devil's ivy (600× magnification) Raphides ( ; singular raphide or raphis'') are needle-shaped crystals of calcium oxalate monohydrate (prismatic monoclinic crystals) or calcium carbonate as aragonite (dipyramidal orthorhombic crystals), found in more than 200 families of plants. Both ends appear needle-like, but raphides tend to be blunt at one end and sharp at the other.

Zhemchuzhnikovite is an oxalate mineral of organic origin; formula NaMg(FeAl)C2O4·8H2O. It forms smoky green crystals with a vitreous lustre and is found in Russian coal mines. It is named after Yury Zhemchuzhnikov (1885–1957), a Russian clay mineralogist.

Weddellite (CaC2O4·2H2O) is a mineral form of calcium oxalate named for occurrences of millimeter-sized crystals found in bottom sediments of the Weddell Sea, off Antarctica. Occasionally, weddellite partially dehydrates to whewellite, forming excellent pseudomorphs of grainy whewellite after weddellite's short tetragonal dipyramids. It was first described in 1936 but only named in 1942.

Moolooite is a rare blue-green mineral with the formula Cu(C2O4)·n(H2O) (n<1) (copper(II) oxalate hydrate). It was discovered in Bunbury Well, Mooloo Downs station, Murchison, Western Australia in 1986. It has an orthorhombic crystalline structure, and is formed by the interaction of bird guano with weathering copper sulfides.

Humboldtine is a rarely occurring mineral from the mineral class of "organic compounds" with the chemical composition FeC2O4•2H2O and is therefore a water-containing iron(II) oxalate or the iron salt of oxalic acid.

Alterite (IMA symbol: Atr) is a yellow-green mineral with the chemical formula ZnFe(SO)(CO)(OH)·17HO. Its type locality is Coconino County, Arizona. It is found exclusively in logs that have mineralized.

Antipinite (IMA symbol: Atp) is a rare alkali Copper oxalate mineral with the chemical formula . Its type locality is the Tarapacá Region in Chile.

Uroxite is an oxalate mineral first discovered as part of the Carbon Mineral Challenge. It is the first discovered uranium-containing organic mineral.

Glushinskite is an oxalate mineral and the mineral form of magnesium oxalate. Occurrences of glushinskite are commonly associated with the growth of lichen on serpentinite.