Aurichalcite

Basic carbonate of zinc and copper
(Zn,Cu)5[(OH)3|CO3]2IMA symbolAch[1]Strunz classification5.BA.15Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP21/mUnit cella = 13.82, b = 6.419
c = 5.29 [Å]
β = 101.04°; Z = 2IdentificationColorPale green, greenish blue, light blue; colorless to pale blue, pale green in transmitted lightCrystal habitTypically in tufted divergent sprays or spherical aggregates, may be in thick crusts; rarely columnar, laminated or granularTwinningObserved in X-ray patternsCleavage{010} and {100} PerfectFractureUnevenMohs scale hardness2LusterPearly, silkyStreakLight blueDiaphaneityTransparentSpecific gravity3.96Optical propertiesBiaxial (−)Refractive indexnα = 1.655 nβ = 1.740 nγ = 1.744Birefringence0.0890PleochroismWeak colorless to pale green2V 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]

Occurrence

Aurichalcite typically occurs in the oxidized zone of copper and zinc deposits. Associated minerals include: rosasite, smithsonite, hemimorphite, hydrozincite, malachite and azurite.[2]

It was first described in 1839 by Bottger who named the mineral for its zinc and copper content after the Greek όρειχαλκος, for "mountain brass" or "mountain copper", the name of orichalcum, a fabulous metal, mentioned in the legend of the mythic lost continent Atlantis. The type locality is the Loktevskoye Mine, Upper Loktevka River, Rudny Altai [ru], Altai Krai, Western Siberia, Russia.[3]

Crystallography

Aurichalcite displays prismatic crystals often in the form of encrustations and sometimes columnar structures.[6] The crystal system is monoclinic.

References

  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 Handbook of Mineralogy
  3. ^ a b c Mindat
  4. ^ Webmineral data
  5. ^ "Minerals Colored by Metal Ions". minerals.gps.caltech.edu. Retrieved 2023-03-01.
  6. ^ "Aurichalcite Mineral Data." https://www.mindat.org/min-422.html Accessed 18 February 2019.
Wikimedia Commons has media related to Aurichalcite.