Andyrobertsite, (Holotype Specimen)

Andyrobertsite


Composition: KCdCu5(AsO4)4[As(OH)2O2].2H2O
Crystal System : Monoclinic
Colours: Electric-blue
Lustre : Vitreous
Hardness (H) : 3
Specific Gravity (S.G) : 4.01
Year of Discovery: 1996
IMA Number: 1997-022
IMA Status: Approved
Discovered By: W.W. (Bill) Pinch (American collector)
Named for: Andrew Roberts (Canadian mineralogist)
References: Cooper et al. (1999)

Tsumeb is the Type Locality

Distribution

Extremely rare. The specimen from which andyrobertsite was eventually described (in 1999) is believed to have been recovered from the first oxidation zone in the 1950s. Andyrobertsite has subsequently been reported from 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 andyrobertsite and stranskiite have been found filling fractures in tennantite-rich massive sulphide ores from the third oxidation zone.

Paragenetic and General Notes

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