Cornwallite is an uncommon

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 pinkish ...

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 ( ...

with formula Cu₅(AsO₄)₂(OH)₄. It forms a series with the

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

pseudomalachite and is a

dimorph In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism ...

of the

triclinic 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...

cornubite Cornubite is a rare secondary copper arsenate mineral with formula: Cu5(AsO4)2(OH)4. It was first described for its discovery in 1958 in Wheal Carpenter, Gwinear, Cornwall, England, UK.Claringbull, Hey and Davis, ''American Mineralogist'' (195 ...

. It is a green

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 ...

mineral which forms as radial to fibrous encrustations. Cornwallite-Baryte-54193

Discovery and occurrence

It was first described in 1846, for an occurrence in Wheal Gorland, St Day United Mines of the St Day District,

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 Atlan ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

. It occurs as secondary mineral in the

oxidized 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 de ...

zone of copper sulfide deposits. Associated minerals include

olivenite Olivenite is a copper arsenate mineral, formula Cu2 As O4O H. It crystallizes in the monoclinic system (pseudo-orthorhombic), and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. More commonly ...

arthurite Arthurite is a mineral composed of divalent copper and iron ions in combination with trivalent arsenate, phosphate and sulfate ions with hydrogen and oxygen.Frost R. L., Duong L., Martens W. (2003) Molecular assembly in secondary minerals ...

clinoclase Clinoclase is a hydrous copper arsenate mineral, Cu3AsO4(OH)3. Clinoclase is a rare secondary copper mineral and forms acicular crystals in the fractured weathered zone above copper sulfide deposits. It occurs in vitreous, translucent dark blue to ...

, chalcophyllite, strashimirite, lavendulan,

tyrolite Tyrolite is a hydrated calcium copper arsenate carbonate mineral with formula: Ca Cu5( As O4)2 CO3(O H)4·6 H2O. Tyrolite forms glassy blue to green orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal sys ...

, spangolite, austinite,

conichalcite Conichalcite, Ca Cu( As O4)(O H), is a relatively common arsenate mineral related to duftite ( PbCu(AsO4)(OH)). It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudanti ...

brochantite Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is Cu4SO4(OH)6. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it was named by Armand Lévy for his fellow Frenchman, geologi ...

azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic car ...

and

malachite Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fracture ...

References

{{Reflist Arsenate minerals Monoclinic minerals Minerals in space group 14

Discovery and occurrence

See also

References