Rittmannite

rittmannite

kryzhanovskite

frondelite

hureaulite

Images

Formula: (Mn2+,Ca)Mn2+(Fe2+,Mn2+,Mg)2(Al,Fe3+)2(PO4)4(OH)2.8H2O
Hydrated phosphate, whiteite subgroup, jahnsite group, manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.81 measured, 2.83 calculated
Hardness: 3½
Streak: White
Colour: Very pale yellow to lemon-yellow, brownish yellow
Common impurities: Mg
Environments

Pegmatites

Localities

At the type locality, the Cubos-Mesquitela-Mangualde area, Mangualde, Viseu, Portugal, granites were emplaced in mica schist and gneiss. A complex of zoned veins of pegmatite cuts the granites. Starting from the granite, their zoning is as follows:
an aplitic periphery 2 cm thick,
a fine-grained pegmatite with abundant mica, quartz and feldspar 20 cm thick,
a coarse-grained pegmatite with smoky quartz, pink orthoclase and white plagioclase 300 to 350 cm thick,
a coarse-grained pegmatite like the previous one, bearing uraniferous micas, lithium - manganese - iron bearing phosphates (nodules) and manganese oxides, 800 cm thick
The samples came from phosphatic nodules of one of the thicker veins within a two-mica granite.
Rittmannite was found on two small (1 x 1 x 1 cm3) phosphate specimens, consisting of crystallised red-brown, skeletal kryzhanovskite, black needle-like frondelite, pink vitreous hureaulite and white massive adularia. It is likely that rittmannite was the last to form in this sequence. The average crystal dimensions are 0.3 x 0.3 x 0.04 mm3 (CM 27.3.447-449).
Rittmannite from the Cubos-Mesquitela-Mangualde area - Image

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