Andyrobertsite, (Holotype Specimen)

Calcioandyrobertsite


Composition: KCaCu5(AsO4)4[As(OH)2O2].2H2O
Crystal System : Orthorhombic; Monoclinic
Colours: Electric-blue; greenish-blue
Lustre : Vitreous
Hardness (H) : 3
Specific Gravity (S.G) : 4.01
Year of Discovery: 1996
IMA Number: 1997-023
IMA Status: Approved
Discovered By: W.W. (Bill) Pinch (American collector)
Named for: Composition/relationship (to andyrobertsite)
References: Cooper et al. (1999)

Tsumeb is the Type Locality

Distribution

Extremely rare. The specimen from which calcioandyrobertsite was eventually described (in 1999) is believed to have been recovered from the first oxidation zone in the 1950s. Also in the third oxidation zone.

Occurrence

  • Supergene
  • 1st Oxidation Zone
  • 3rd Oxidation Zone

Notable Finds

The type-specimen (W.Pinch collection, probably from the first oxidation zone) has attained iconic status. Subsequently, microcrystalline mixtures of calcioandyrobertsite and stranskiite have been found filling fractures in tennantite-rich massive sulphide ores fro the third oxidation zone.

Paragenetic and General Notes

The type assemblage comprises calcioandyrobertsite (with andyrobertsite) on tennantite, with adamite (cuprian), and olivenite. Note that calcioandyrobertsite and andyrobertsite occur as an intimate lamellar intergrowth and are not visually distinguishable.