What are arsenates in mineralogy ?
Arsenates : definition
Arsenates form a subclass belonging to the mineralogical class of "phosphates, arsenates, vanadates"; they are built from tetrahedral anionic groups (AsO4)3- and different cations.
They are relatively rare, frequently hydrated minerals, the most common of which seem to be scorodite and olivenite. Equivalent (PO4)3- and (VO4)3- tetrahedral units are the basis of phosphates and vanadates. P5+, As5+, V5+ are easily replaced in the anionic groups, there are many transition terms between phosphates, arsenates and vanadates : pyromorphite Pb5(PO4)3Cl, mimetite Pb5(AsO4)3Cl and vanadinite Pb5(VO4)3Cl, for example between them form extended (but not complete) series.
They are relatively rare, frequently hydrated minerals, the most common of which seem to be scorodite and olivenite. Equivalent (PO4)3- and (VO4)3- tetrahedral units are the basis of phosphates and vanadates. P5+, As5+, V5+ are easily replaced in the anionic groups, there are many transition terms between phosphates, arsenates and vanadates : pyromorphite Pb5(PO4)3Cl, mimetite Pb5(AsO4)3Cl and vanadinite Pb5(VO4)3Cl, for example between them form extended (but not complete) series.
Adamite from Mapimi, Mexico
Mimetite from Pingtouling, China
Roselite from Bou Azzer, Morocco