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Formula: NaNa2(Mn2+4Fe3+)Si8O22(OH)2
Inosilicate (chain silicate),
eckermannite root name group,
sodium amphibole subgroup,
amphibole supergroup,
manganese-bearing mineral
Specific gravity: 3.3
Hardness: 5
Streak: Light purplish brown
Colour: Reddish-black to black
Common impurities: Cr,Zn,Mg,Ca,K,H2O
Environments
Localities
At the type locality, the Tanohata mine, Tanohata, Shimohei District, Iwate Prefecture, Japan, mangano-ferri-eckermannite occurs
as banded aggregates of short prismatic crystals up to 2 cm long in the manganese deposit,
where sedimentary beds have been metamorphosed by the intrusion of granodiorite.
Associated minerals include braunite, rhodonite,
manganiferous alkali pyroxene and
amphibole, and quartz
(AM 55.1810-1818).
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