Mineral Type - Purpurite
Formula: (Mn3+,Fe3+)PO4
Purpurite forms by leaching of Li out of its site leaving a vacancy and by oxidation of divalent Mn.
Colour: Dark purple to purplish red.
Lustre: Dull, Earthy
Hardness: 4 - 4½
Specific Gravity: 3.2 - 3.4
Crystal System: Orthorhombic
Name: Named in 1905 by Louis C. Graton and Waldemar T. Schaller from the Latin "purpura" in allusion to its colour.
Type Locality: ⓘFaires Mine, Kings Mountain, Gaston Co., North Carolina, USA
Purpurite is the trivalent Mn-dominant, Li-deficient oxidation product of lithiophilite. The species of the Heterosite-Purpurite Series are secondary minerals formed by oxidation of iron and or manganese with the simultaneous leaching of lithium, primarily from their respective parent species, lithiophilite and triphylite. Intermediate alteration products are part of a continuous process of alteration: Ferrisicklerite and Sicklerite, are intermediate between unoxidized and unleached end-members and the completely leached and appropriately oxidized end-products, but may not be valid species. The Mn:Fe value has not been observed to vary much from the primary lithiophilite to the secondary purpurite.
