Mesaite

Mesaite is a very rare mineral with formula CaMn²⁺₅(V₂O₇)₃•12H₂O. It is monoclinic (space group P2/n). It is related to fianelite, another manganese-rich divanadate. Examples of other divanadate minerals are volborthite, engelhauptite, karpenkoite, and martyite. ^{[1][2][3][4][5][6]}