Olivenite is a

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

arsenate mineral Arsenate minerals usually refer to the naturally occurring orthoarsenates, possessing the (AsO4)3− anion group and, more rarely, other arsenates with anions like AsO3(OH)2− (also written HAsO42−) (example: pharmacolite Ca(AsO3OH).2H2O) or (v ...

, formula Cu₂ As O₄O H. It crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

system (pseudo-orthorhombic), and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. More commonly, it occurs as globular aggregates of acicular crystals, these fibrous forms often having a velvety luster; sometimes it is lamellar in structure, or soft and earthy. A characteristic feature, and one to which the name alludes (German, ''Olivenerz'', of

A. G. Werner Abraham Gottlob Werner (; 25 September 174930 June 1817) was a German geologist who set out an early theory about the stratification of the Earth's crust and propounded a history of the Earth that came to be known as Neptunism. While most tene ...

, 1789), is the olive-green color, which varies in shade from blackish-green in the crystals to almost white in the finely fibrous variety known as ''woodcopper''. The hardness is 3, and the

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

is 4.3. The mineral was formerly found in some abundance, associated with

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

, in the upper workings in the

mines of the

St Day St Day ( kw, Sen Day) is a civil parishes in England, civil parish and village in Cornwall, England, United Kingdom. It is situated between the village of Chacewater and the town of Redruth. The electoral ward St Day and Lanner, Cornwall, Lanner ...

district in

Cornwall Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...

; also near

Redruth Redruth ( , kw, Resrudh) is a town and civil parishes in Cornwall, civil parish in Cornwall, England. The population of Redruth was 14,018 at the 2011 census. In the same year the population of the Camborne-Redruth urban area, which also inc ...

, and in the Tintic Mining District in

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

. It is a mineral of secondary origin, a result of the

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

of copper ores and

arsenopyrite Arsenopyrite ( IMA symbol: Apy) is an iron arsenic sulfide (FeAsS). It is a hard ( Mohs 5.5-6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases eleme ...

. The

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...

of olivenite is sometimes partly replaced by a small amount of

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

, and in the species

libethenite Libethenite is a rare copper phosphate hydroxide mineral. It forms striking, dark green orthorhombic crystals. It was discovered in 1823 in Ľubietová, Slovakia and is named after the German name of that locality (''Libethen''). Libethenite has a ...

we have the corresponding copper phosphate Cu₂ PO₄OH. This is found as small dark green crystals resembling olivenite at

Ľubietová Ľubietová (german: Libethen) is a village in central Slovakia. Originally an ancient mining town, it is known for precious minerals. Geography Ľubietová is part of the Banská Bystrica District in the Banská Bystrica Region. It is situated 25 ...

in the

Slovak Republic Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...

, and in small amount also in Cornwall. Other members of this isomorphous group of minerals are

adamite Adamite is a zinc arsenate hydroxide mineral, Zn2 As O4O H. 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 a ...

, Zn₂AsO₄OH, and

eveite Eveite is a manganese arsenate mineral in the olivenite group. Its chemical formula is Mn2AsO4OH. It is found only in Långban, Filipstad, Värmland, Sweden and at the Sterling Mine in New Jersey New Jersey is a state in the Mid-Atlan ...

, Mn₂AsO₄OH.

References

*{{1911, wstitle=Olivenite Copper(II) minerals Arsenate minerals Monoclinic minerals Minerals in space group 14