Chalcophyllite Locality: Piesky, Špania Dolina (Urvölgy; Herrengrund), Špania Dolina ore belt, Starohorské Mts, Banská Bystrica Region, Slovakia Picture width 1 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Chalcophyllite
A rare secondary copper arsenate forming paper-thin platy crystals in oxidized copper deposits, first described from Germany.
Intro adapted from Wikipedia (CC BY-SA).
Chalcophyllite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₁₈Al₂(AsO₄)₄(SO₄)₃(OH)₂₄·36H₂O.
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Chalcophyllite structural group.
Key properties: Mohs hardness 2; specific gravity 2.67–2.69; Pale green to bluish green streak; Vitreous to subadamantine, pearly on {0001} luster; refractive index 1.595; optically uniaxial.
IMA symbol Chp, grandfathered status — known before the IMA’s founding, named in 1841.
A rare secondary mineral found in the oxidized zone of some arsenic-bearing hydrothermal polymetallic deposits.
It is found associated with Azurite, malachite, brochantite, chrysocolla, spangolite, connellite, cuprite, cyanotrichite, strashimirite, parnauite, lavendulan, cornubite, langite.
Its name comes from the Greek for copper and a leaf, for its prominent micaceous appearance.