Botallackite

Halide mineral

(repeating unit)Cu2(OH)3ClIMA symbolBlk[1]Strunz classification3.DA.10bCrystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP21/mUnit cella = 5.717 Å,
b = 6.126 Å,
c = 5.636 Å; β = 93.07°; Z = 2IdentificationColourShades of greenCrystal habitPlaty interlaced crystal crustsCleavage{100} PerfectMohs scale hardnessSoftDiaphaneityTransparent to translucentSpecific gravity3.6Optical propertiesBiaxial (+)Refractive indexnα= 1.775, nβ= 1.800, nγ= 1.846Birefringenceδ = 0.071PleochroismWeak – blue green shadesDispersionr > v, strongReferences[2][3][4]

Botallackite, chemical formula Cu2(OH)3Cl is a secondary copper mineral, named for its type locality at the Botallack Mine, St Just in Penwith, Cornwall. It is polymorphous with atacamite, paratacamite and clinoatacamite [Wikidata].[2]

Botallackite crystallises in the monoclinic crystal system. It is mountain-green to green in colour, with one distinct to good cleavage.[2]

Discovery and occurrence

It was first described in 1865 for an occurrence in the Botallack mine, Cornwall, England, and named for the type locality.[2]

Botallackite forms in copper deposits exposed to weathering and salt water.[2] It is reported from black smoker 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 atacamite, paratacamite, brochantite, connellite and gypsum.[3]

References

  • Minerals portal
  • flagCornwall portal
  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c d e Mindat information page for Botallackite
  3. ^ a b Handbook of Mineralogy
  4. ^ Webmineral data
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