arsenate mineral

Arsenate minerals usually refer to the naturally occurring orthoarsenates, possessing the (AsO₄)^3- anion group and, more rarely, other arsenates with anions like AsO₃(OH)^2- (also written HAsO₄^2-) (example: pharmacolite Ca(AsO₃OH)^.2H₂O) or (very rarely) [AsO₂(OH)₂]^- (example: andyrobertsite). Arsenite minerals are much less common. Both the Dana and the Strunz mineral classifications place the arsenates in with the phosphate minerals.