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. (2 ...

, named for its type locality at the

Botallack Mine The Botallack Mine ( kw, Bostalek) is a former mine in Botallack in the west of Cornwall, UK. Since 2006 it has been part of the UNESCO World Heritage Site – Cornwall and West Devon Mining Landscape. The mine is within the Aire Point to Ca ...

St Just in Penwith St Just ( kw, Lan(n)ust), known as St Just in Penwith, is a town and civil parish in the Penwith district of Cornwall, England, United Kingdom. It lies along the B3306 road which connects St Ives to the A30 road. The parish encompasses th ...

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 ...

. It is

polymorphous Polymorphism, polymorphic, polymorph, polymorphous, or polymorphy may refer to: Computing * Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms * Ad hoc polymorphis ...

with

atacamite Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described for deposits in the Atacama Desert of Chile in 1801 by D. de Fallizen. The Atacama Desert is also the namesake of the mineral. ...

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, Australia, and in Italy in Capo Calamita ...

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 s ...

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 poin ...

. 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. 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 movement) ...

and salt water. It is reported from

black smoker A hydrothermal vent is a fissure 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 hotspot ...

deposits due to reaction of primary sulfide minerals with seawater. It also occurs on copper bearing slag exposed to seawater. Minerals associated with botallackite include

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, geologist ...

, 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 drywal ...

References

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