Purpurite

purpurite

triphylite

heterosite

sicklerite

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Formula:(Mn3+,Fe3+)(PO4)
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
Environments

Pegmatites

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).

Localities

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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