Plancheite

{{Short description|Hydrated copper silicate mineral}} {{Infobox mineral | name = Plancheite | category = Inosilicate | image = Plancheite and Malachite.jpg | caption = Plancheite and Malachite, Milpillas mine, Sonora, Mexico | imagesize = 300px | formula = Cu₈Si₈O₂₂(OH)₄•(H₂O) | IMAsymbol = Pch<ref>{{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}}</ref> | molweight = 1,171 g/mol | strunz = 9.DB.35 (10 ed) <br /><small>8/F.05-10 (8 ed)</small> | dana = 66.2.1.1 | system = Orthorhombic | class = Dipyramidal (mmm) <br/>H-M symbol: (2/m 2/m 2/m) | symmetry = Orthorhombic <br/>Space group: ''Pcnb'' | color = Pale blue, light blue, dark green | habit = Acicular, Fibrous, or Radial | twinning = | cleavage = None observed | fracture = | mohs = 5.5 to 6 | luster = Vitreous to silky | refractive = Nx = 1.645, Ny = 1.660 Nz = 1.715<ref name=mindat/><ref name=webmin/><ref name=Dana/><br/> Nx = 1.697, Ny = 1.718, Nz = 1.741<ref name=HOM/><ref name=AM62>Evans and Mrose (1977) American Mineralogist 62:491-502</ref> | birefringence = | pleochroism = X colorless or pale blue, Y colorless or blue, Z blue or dark blue | streak = Light blue | gravity = 3.6 to 3.8 | melt = | fusibility = | diagnostic = | opticalprop = Biaxial (+) | solubility = | diaphaneity = Translucent to opaque | other = Nonfluorescent, nonmagnetic, not radioactive | references =<ref name=Dana>Gaines et al (1997) Dana's New Mineralaogy, Wiley</ref><ref name=webmin>[http://www.webmineral.com/data/Plancheite.shtml Webmineral]</ref><ref name=mindat>[http://www.mindat.org/min-3233.html Mindat]</ref><ref name=HOM>[http://www.handbookofmineralogy.org/pdfs/plancheite.pdf Handbook of Mineralogy]</ref>}}

'''Plancheite''' is a hydrated copper silicate mineral with the formula Cu₈Si₈O₂₂(OH)₄•(H₂O). It is closely related to shattuckite in structure and appearance, and the two minerals are often confused.

==Structure== Plancheite is a chain silicate (inosilicate), with double chains of silica tetrahedra parallel to the c crystal axis.<ref name=AM62/> It occurs as sprays of acicular or fibrous radial clusters, with fibers extended parallel to the chains, i.e. along the c crystal axis;<ref name=HOM/> it can also form tiny tabular or platy crystals. It is a member of the orthorhombic crystal class m m m (2/m 2/m 2/m), which is the most symmetrical class in the orthorhombic system.

==Properties== Usually a pale turquoise-blue, with a pale blue streak and an adamantine to silky luster. It is quite hard, with hardness 5.5 to 6, close to that of feldspar, and specific gravity 3.6 to 3.8. Optically it is biaxial (+), with refractive indices between 1.64 and 1.74, and pleochroic.<ref name="mindat"/><ref name="webmin"/><ref name="Dana"/><ref name="HOM"/>

==Environment== Plancheite is a secondary mineral formed in the oxidized zone of copper deposits, associated with other copper minerals chrysocolla, dioptase, malachite, conichalcite and tenorite.<ref name=HOM/> It occurs with primary malachite at the Milpillas Mine in Mexico.<ref name=MinRec39>Moore and Origlieri (2008) Mineralogical Record 39-6:25-34</ref> The type locality is the Sanda Mine, Mindouli, Pool Region, Republic of Congo.<ref name=mindat/> [[File:Plancheite-35235.jpg|thumb|left|Plancheite, Kolwezi, Katanga (Shaba), Democratic Republic of Congo. 5.9 x 3.2 x 2.6 cm.]]

{{clear}} ==References== {{Reflist}}

==External links== JMol: http://rruff.geo.arizona.edu/AMS/viewJmol.php?id=00578

{{Commons category}}

Category:Copper(II) minerals Category:Inosilicates