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Formula: NaMn2+4Si5O14(OH)
Inosilicate (chain silicate), forms a series with nambulite,
rhodonite group,
manganese-bearing mineral
Crystal System: Triclinic
Specific gravity: 3.51 measured, 3.50 calculated
Hardness: 5½ to 6
Streak: White
Colour: Pinkish orange
Common impurities: Fe,Mg,Ca,H2O
Environments:
Pegmatites
Metamorphic environments
Localities
At the Gozaisho mine, Iwaki City, Fukushima Prefecture, Japan, isomorphic
nambulite, natronambulite,
marsturite and
lithiomarsturite have been found. They belong to the
pectolite-pyroxene series of
minerals, with five-periodic single chains of tetrahedra
(AM 99.1462-1470).
At the type locality, the Tanohata mine, Tanohata-mura, Shimohei District, Iwate Prefecture, Japan,
natronambulite occurs in
contact metamorphosed low-grade banded
manganese ore (Mindat, MJ 12.332-340), associated with
manganoan aegirine,
manganoan arfvedsonite,
quartz and rhodonite. It also
occurs as an accessory
mineral in an
albite-microcline-quartz
pegmatite cutting the ore (MJ 12.332-340, HOM), associated with
aegirine,
manganoan arfvedsonite,
rhodonite, mangano-ferri-eckermannite,
marsturite, serandite,
quartz, albite and
microcline
(HOM).
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