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 substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

, named for its type locality at the Botallack Mine in

St Just in Penwith St Just (), also known as St Just in Penwith, is a town and civil parishes in England, civil parish in the Penwith district of Cornwall, England, United Kingdom. It lies along the B3306 road which connects St Ives, Cornwall, St Ives to the A3 ...

, Cornwall. It is polymorphous with atacamite, paratacamite 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 Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

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 (an infinite array of discrete points). Space groups (symmetry groups ...

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

cleavage Cleavage may refer to: Science * Cleavage (crystal), the way in which a crystal or mineral tends to split * Cleavage (embryo), the division of cells in an early embryo * Cleavage (geology), foliation of rock perpendicular to stress, a result of ...

Discovery and occurrence

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

Cornwall Cornwall (; or ) is a Ceremonial counties of England, ceremonial county in South West England. It is also one of the Celtic nations and the homeland of the Cornish people. The county is bordered by the Atlantic Ocean to the north and west, ...

, England, and named for the type locality. 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, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

and salt water. It is reported from

black smoker Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hots ...

deposits due to reaction of primary sulfide minerals with seawater. It also occurs on copper bearing

slag The general term slag may be a by-product or co-product of smelting (pyrometallurgical) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be c ...

exposed to seawater. Minerals associated with botallackite include atacamite, paratacamite, brochantite, connellite and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, 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, drywall and blackboard or sidewalk ...

References

Copper(II) minerals Chloride minerals Monoclinic minerals Minerals in space group 11 Minerals described in 1865 {{Halide-mineral-stub