PURPURITE

Purpurite de Helen Beryl Mine, Dakota du Sud, USA © Harold Moritz

    Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous phosphates
    Crystal system : Orthorhombic
    Chemistry : MnPO4
    Rarity : Quite common

Purpurite is a manganese phosphate which forms a continuous series with heterosite (ferriferous). It is a secondary phosphate coming from the alteration of primary phosphates (notably triphylite and lithiophyllite) which is found in granitic pegmatites. Its name comes from the Latin purpura (purple) in allusion to its color. It does not form crystals but cleavable masses, sometimes pseudomorph after triphylite, or thin encrustations of carmine red to purple or purplish pink, turning brown-black then black by superficial oxidation. It is sometimes cut into a cabochon and used in jewelry.


Main photo : Purpurite from Helen Beryl Mine, Dakota du Sud, USA © Harold Moritz

Purpurite in the World

Purpurite is a relatively common phosphate but rarer than heterosite. It is found in notable masses in numerous American pegmatites in South Dakota (Custer Mountain), Maine (Newry, Greenwood), California (Pala Chief, Rincon) and Colorado (Crystal Mountain, the latter having provided cleavable masses 20 cm). Among its other deposits are the lepidolite pegmatites of the Karibib region (Namibia) and that of Mangualde (Portugal).

Right photo : 47,00 ct purpurite cabochon from Namibia

Purpurite in France

In France, the lepidolite pegmatites of St-Sylvestre and Chanteloube in the Monts d'Ambazac (Haute-Vienne) gave centimeter-sized cleavable masses of purpurite.

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 4 to 4.5
Density : 3.2 to 3.4
Fracture : Irregular
Streak : Purple

TP : Opaque
RI : 1.852 to 1.922
Birefringence : 0.040
Optical character : Biaxial +
Pleochroism : Strong
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None

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