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 HAsO42−) (example: pharmacolite Ca(AsO3OH).2H2O) or (very rarely) [AsO2(OH)2]− (example: andyrobertsite).
Arsenite minerals are much less common.
[1] Both the Dana[2] and the Strunz[3] mineral classifications place the arsenates in with the phosphate minerals.
Example arsenate minerals include: IMA-CNMNC proposes a new hierarchical scheme (Mills et al., 2009).
This list uses it to modify the Classification of Nickel–Strunz (mindat.org, 10 ed, pending publication).