Melanotekite

sorosilicate

Långban

Formula: Pb2Fe3+2O2(Si2O7) sorosilicate (Si2O7 groups)
Specific gravity: 5.73 to 6.19
Hardness: 6½
Streak: Greenish
Colour: Grey, black
Solubility: Decomposed by nitric acid
Environments:

Pegmatites
Metamorphic environments

Melanotekite occurs with native lead at the type locality, Långban, Sweden, in a pre-Cambrian metamorphosed Fe-Mn deposit. At Artillery Peaks, Arizona, USA it is found in oxidised Pb-Cu ores, and at Dara-i-Pioz, Tajikistan, it occurs in an aluminium-poor, sodium and potassium-rich pegmatite.
At 650oC, melanotekite can coexist with quartz, hematite, magnetoplumbite and plumboferrite.
Common impurities: Ti,Al,Mn,Mg

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