Anhydrous normal phosphate, triphylite group, forms a series with heterosite
Specific gravity: 3.2 to 3.4
Hardness: 4 to 4½
Streak: Light to medium purple, lighter than the colour of the massive mineral
Colour: Dark purple to purplish red
Solubility: Soluble in hydrochloric acid
Common impurities: Fe
Purpurite is a secondary mineral derived from oxidation and
leaching of primary manganese-iron phosphates, particularly
lithiophilite, in complex
granite pegmatites; the purpurite leaches
lithium out of its
site, leaving a vacancy, and oxidises divalent manganese Mn2+ to trivalent manganese Mn3+
(HOM, Mindat, Dana).
Rarely, purpurite is formed by reaction between bat guano and iron-manganese deposits resulting from seawater ingress (HOM).
Associated minerals include lithiophilite, sicklerite and many secondary iron-manganese phosphates (HOM).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, purpurite forms in some pods as the major replacement of lithiophilite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.513-514).
At the type locality, the Faires Mine, Kings Mountain, Gaston county, North Carolina, USA, purpurite occurs in oxidised and leached primary lithiophilite pods from a granite pegmatite (Mindat).
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