Arsenoclasite (originally arsenoklasite) is a red or dark orange brown mineral with formula Mn₅(AsO₄)₂(OH)₄. The name comes from the Greek words ''αρσενικόν'' (for arsenic) and ''κλάσις'' (for cleavage), as arsenoclasite contains arsenic and has perfect cleavage. The mineral was discovered in 1931 in Långban, Sweden.

Description

Arsenoclasite is red or dark orange brown in color. The mineral rarely occurs as crystals; rather it has either a massive or granular habit. When crystals are present, they are no larger than . Arsenoclasite has been found in association with adelite,

allactite 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 Greek αλλάκτειν (allaktein) meaning "to change", referring to the strong pleochroism ...

barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

, dolomite,

gatehouseite Gatehouseite is a manganese hydroxy phosphate mineral with formula Mn5(PO4)2(OH)4. First discovered in 1987, it was identified as a new mineral species in 1992 and named for Bryan M. K. C. Gatehouse (born 1932). , it is known from only one mine i ...

, hausmannite,

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

, manganoan ferroan calcite,

sarkinite Sarkinite, synonymous with chondrarsenite and polyarsenite, is a mineral with formula Mn2(AsO4)(OH). The mineral is named for the Greek word ''σάρκιυος'', meaning made of flesh, for its red color and greasy luster. The mineral was first no ...

, and shigaite. The mineral occurs in fissures of metamorphosed Fe- Mn ore bodies and sedimentary Fe-Mn deposits.

Structure

A 1971 study identified the mineral's structure as an array of oxygen atoms in a double hexagonal close packed pattern. However, a 1977 study discovered that all the manganese ions in arsenoclasite are six-coordinated, a constraint this structure cannot permit without severe distortion. The 1977 study identified arsenoclasite as isostructural to Co₅(PO₄)₂(OH)₄ and Mn₅(PO₄)₂(OH)₄.

History

Arsenoclasite was noted from specimens at Långban, Värmland, Sweden, by Gust Flink in 1924 as a mineral that appeared similar to

, but with one perfect cleavage. Arsenoclasite was discovered in Långban and officially identified by G. Aminoff in 1931 under the name arsenoklasite. The samples observed by Aminoff did not occur as crystals.

Distribution

, arsenoclasite is known from Långban, Sweden, the Valgraveglia Mine in Liguria, Italy, and the Iron Monarch open cut in South Australia. The type material is held at the

Swedish Museum of Natural History The Swedish Museum of Natural History ( sv, Naturhistoriska riksmuseet, literally, the National Museum of Natural History), in Stockholm, is one of two major museums of natural history in Sweden, the other one being located in Gothenburg. The ...

in Stockholm and the Natural History Museum, London.

References

Bibliography

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External links

Photos of arsenoclasite
from mindat.org Manganese(II) minerals Arsenate minerals Orthorhombic minerals Minerals in space group 19