Andyrobertsite is a rare, complex arsenate mineral with a blue color. It is found in the Tsumeb mine in Namibia and named after Andrew C. Roberts (b. 1950), a mineralogist with the Geological Survey of Canada. A Ca-rich analog (with Ca instead of Cd) is called calcioandyrobertsite and has a more greenish tint.

General Information

  • Category: Arsenate mineral
  • Formula: KCdCu5(AsO4)4(H2AsO4)·2H2O
  • Crystal system: Monoclinic
  • Crystal class: Prismatic (2/m).


It looks electric blue with a pale-blue streak, a vitreous luster, and they do not fluoresce under longwave or shortwave ultraviolet light. The aggregate has a Mohs hardness of 3, is brittle with a conchoidal fracture, and has good cleavage parallel to (100).

  • Color: Blue
  • Crystal habit: Platy
  • Mohs scale hardness: 3
  • Luster: Vitreous
  • Streak: Pale blue
  • Diaphaneity: Transparent
  • Specific gravity: 4.


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