Botallackite

{{short description|Halide mineral}}

{{Use dmy dates|date=April 2022}}

{{Infobox mineral

| name = Botallackite

| category = Halide minerals

| boxwidth =

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| image = Botallackite-sea82b.jpg

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| caption = Botallackite from the Levant Mine, Cornwall

| formula = Cu₂(OH)₃Cl

| IMAsymbol=Blk{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| strunz = 3.DA.10b

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = P2₁/m

| unit cell = a = 5.717 Å,
b = 6.126 Å,
c = 5.636 Å; β = 93.07°; Z = 2

| colour = Shades of green

| habit = Platy interlaced crystal crusts

| twinning =

| cleavage = {100} Perfect

| fracture =

| tenacity =

| mohs = Soft

| luster =

| polish =

| refractive = n_α= 1.775, n_β= 1.800, n_γ= 1.846

| opticalprop = Biaxial (+)

| birefringence = δ = 0.071

| dispersion = r > v, strong

| pleochroism = Weak – blue green shades

| fluorescence=

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| gravity = 3.6

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| diaphaneity = Transparent to translucent

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| references = [http://rruff.geo.arizona.edu/doclib/hom/botallackite.pdf Handbook of Mineralogy][http://www.webmineral.com/data/Botallackite.shtml Webmineral data]

}}

Botallackite, chemical formula Cu₂(OH)₃Cl is a secondary copper mineral, named for its type locality at the Botallack Mine in St Just in Penwith, Cornwall. It is polymorphous with atacamite, paratacamite and {{interlanguage link|clinoatacamite|qid=Q3680774}}.[http://www.mindat.org/min-732.html Mindat information page for Botallackite]

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