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Formula: Ba4(V3+,Ti)4(O,OH)2[B2Si8O27]Cl
Cyclosilicate (ring silicate), barium-,
vanadium-, titanium- and
boron- bearing mineral
Crystal System: Orthorhombic
Specific gravity: 4.08 measured, 4.14 calculated
Hardness: 6
Streak: Green
Colour: Greenish black
Common impurities: Mn,H2O
Environments
Sedimentary environments
Hydrothermal environments
Localities
At the type locality, the Mogurazawa mine, Kiryu City, Gunma Prefecture, Japan, nagashimalite occurs as
crystals up to 15 mm long in fissures cutting massive rhodonite ore in
bedded chert. Associated minerals include
rhodochrosite, rhodonite,
suzukiite, baryte,
barium-bearing roscoelite,
alabandite, digenite,
bornite, and tetrahedrite
(HOM, Mindat).
Nagashimalite from the Mogurazawa mine -
Image
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