Anhydrous normal phosphate, triphylite group, forms a series with purpurite and with triphylite (Dana).
Specific gravity: 3.40
Hardness: 4 to 4½
Streak: Pale purple
Colour: Usually purple-black, also deep rose to reddish purple, especially when treated in a strong acid solution
Solubility: Readily soluble in hydrochloric acid
Common impurities: Mn
Heterosite is a secondary mineral in the oxidised zone of
complex granite pegmatites, formed by oxidation of iron and or manganese
with the simultaneous leaching of lithium from
usually lithiophilite or
triphylite (Webmin, Mindat, HOM).
Associated minerals include muscovite,
ferrisicklerite and many
secondary iron-manganese phosphates (Mindat, HOM).
At the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Nouvelle-Aquitaine, France, heterosite occurs in a granite pegmatite (Mindat).
At the Chickering Mine, Walpole, Cheshire County, New Hampshire, USA, heterosite is a secondary mineral resulting from the oxidation of triphylite, with ferrisicklerite as an intermediate phase. It is most commonly associated with quartz, albite, muscovite, siderite, and ferrisicklerite (R&M 90.5.418).
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