Aurichalcite

Aurichalcite
General
CategoryCarbonate mineral
Formula
(repeating unit)
(Zn,Cu)5[(OH)3|CO3]2
IMA symbolAch[1]
Strunz classification5.BA.15
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/m
Unit cella = 13.82, b = 6.419
c = 5.29 [Å]
β = 101.04°; Z = 2
Identification
ColorPale green, greenish blue, light blue; colorless to pale blue, pale green in transmitted light
Crystal habitTypically in tufted divergent sprays or spherical aggregates, may be in thick crusts; rarely columnar, laminated or granular
TwinningObserved in X-ray patterns
Cleavage{010} and {100} Perfect
FractureUneven
Mohs scale hardness2
LusterPearly, silky
StreakLight blue
DiaphaneityTransparent
Specific gravity3.96
Optical propertiesBiaxial (−)
Refractive indexnα = 1.655 nβ = 1.740 nγ = 1.744
Birefringence0.0890
PleochroismWeak colorless to pale green
2V angleMeasured: 1° to 4°, Calculated: 22°
References[2][3][4]

Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is (Zn,Cu)5(CO3)2(OH)6. The zinc to copper ratio is about 5:4.[3] Copper (Cu2+) gives aurichalcite its green-blue colors.[5]

  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. ^ Handbook of Mineralogy
  3. ^ a b Mindat
  4. ^ Webmineral data
  5. ^ "Minerals Colored by Metal Ions". minerals.gps.caltech.edu. Retrieved 2023-03-01.