It is a hygroscopic purple solid that absorbs moisture to form the pale-green monohydrate,[1] though the anhydrous and monohydrate forms are typically each synthesized by separate methods.

Manganese phosphate monohydrate is produced by the reaction of an Mn(II) salt, such as manganese(II) sulfate, and phosphoric acid, followed by oxidation by nitric acid.

Another method of producing the monohydrate is by the comproportionation of permanganate and Mn(II) in phosphoric acid:[2][3][4] The diphosphomanganate(III) ion slowly converts to the monohydrate.

Heating of the monohydrate does not yield the anhydrous form, instead, it decomposes to manganese(II) pyrophosphate (Mn2P2O7) at 420 °C:[3] To produce the anhydrous form, lithium manganese(II) phosphate is oxidized with nitronium tetrafluoroborate under inert conditions.

[1] The anhydrous form has an olivine structure and naturally occurs as the mineral purpurite.