Conichalcite

Conichalcite
A thin crust of conichalcite on a rock.
General
CategoryArsenate minerals
Formula
(repeating unit)
CaCu(AsO4)(OH)
IMA symbolCon[1]
Strunz classification8.BH.35
Dana classification41.5.1.2
Crystal systemOrthorhombic
Crystal classDisphenoidal (222)
(same H-M symbol)
Space groupP212121
Unit cella = 7.39(1) Å,
b = 9.23(1) Å,
c = 5.83(1) Å;
V = 397.66 Å³; Z = 4
Identification
ColorGrass-green to yellowish green, pistachio-green, emerald-green; may be zoned; light green to yellowish green in transmitted light.
Crystal habitCrusts of acicular to almost fibrous crystals. Also as botryoidal masses and compact crusts.
TwinningRare on {001}
CleavageAbsent
FractureUneven
TenacityBrittle
Mohs scale hardness4.5
LusterVitreous, greasy
StreakGreen
DiaphaneityTranslucent
Specific gravity4.3
Optical propertiesBiaxial (+/−)
Refractive indexnα = 1.778 – 1.800 nβ = 1.795 – 1.831 nγ = 1.801 – 1.846
Birefringenceδ = 0.023 – 0.046
PleochroismVisible
DispersionStrong r < v to r < v moderate
References[2][3][4]

Conichalcite, CaCu(AsO4)(OH), is a relatively common arsenate mineral related to duftite (PbCu(AsO4)(OH)). It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudantite, adamite, cuproadamite, olivenite and smithsonite.[3][4]

  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. ^ Mineralienatlas
  3. ^ a b Mindat.org
  4. ^ a b Handbook of Mineralogy