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Formula: (Mn2+,Ca)2x(Mn4+)1-xO2.0.7H2O
Hydrated oxide, birnessite group, forms a series with
ranciéite, manganese-bearing mineral
Crystal system: Hexagonal
Specific gravity: 3.41 measured, 3.98 calculated
Hardness: 5
Streak: Dark brown
Colour: Grey, black, grey-brown
Luminescence: Not fluorescent under UV
Solubility: Etch reactions with concentrated hydrochloric acid and with concentrated nitric acid
Environments
Sedimentary environments
Metamorphic environments
Localities
At the type locality, the Nomura mine, Nomura, Seiyo City, Ehime Prefecture, Japan, takanelite occurs in irregularly
shaped nodules 1 to 15 cm across, composed of microscopic intergrowths with
braunite, halloysite,
goethite and quartz, in the oxidation
zone of the braunite -
rhodochrosite -
caryopilite bedded deposit in low-grade metamorphosed
cherts
(AM 56.1487-1489).
At the Janggun mine, Bonghwa County, North Gyeongsang Province, South Korea, takanelite occurs as massive or
colloform (kidney-shaped) bands in nsutite-rich ores of the supergene zone
derived through oxidation of rhodochrosite. It is usually replaced by
nsutite or pyrolusite along the
colloform bands or in a random fashion, showing gradational contacts. The
manganese ore containing this mineral is grey in colour and very hard because
of the presence of abundant nsutite. It is characterized by small, grey shiny or
greasy colloform areas
(AM 76.1426-1430).
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