Botallackite, chemical formula Cu₂(OH)₃Cl is a secondary copper

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

, named for its

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

at the Botallack Mine, St Just in Penwith,

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 ...

. It is polymorphous with atacamite,

paratacamite Paratacamite is a mineral in the halide minerals category. Its chemical formula is . Its name is derived from its association with atacamite. It is found in Chile, Botallack Mine in Cornwall, Broken Hill Broken Hill is an inland mining ...

and .Mindat information page for Botallackite
/ref> Botallackite crystallises 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 ...

crystal system In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices. Space groups are classified into crystal systems according to their poi ...

. It is mountain-green to green in colour, with one distinct to good cleavage.

Discovery and occurrence

It was first described in 1865 for an occurrence in the Botallack mine,

, England, and named for the

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

. Botallackite forms in copper deposits exposed to

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs '' in situ'' (on site, with little or no movemen ...

and salt water. It is reported from black smoker deposits due to reaction of primary sulfide minerals with seawater. It also occurs on copper bearing

slag Slag is a by-product of smelting ( pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/ base metals (by ...

exposed to seawater. Minerals associated with botallackite include atacamite,

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 ...

, connellite and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and dr ...

References

Copper(II) minerals Halide minerals Monoclinic minerals Minerals in space group 11 {{Halide-mineral-stub