Kutnohorite

dolomite

rhodochrosite

Formula: CaMn2+(CO3)2
Anhydrous normal carbonate, dolomite group, forms a series with dolomite and with ankerite, manganese mineral
Specific gravity: 3.12
Hardness: 3½ to 4
Streak: White
Colour: White, pale rose, pink, light to medium brown
Environments

Hydrothermal environments

Kutnohorite occurs typically in hydrothermal deposits associated with manganese-rich sediments, associated with rhodochrosite, aragonite and calcite (HOM).

At the Wutong mine, Guangxi, China, kutnohorite has been found partially coating or completely covering rhodochrosite (Minrec 42.6.540-541).

The type locality is Poličany, Kutná Hora District, Central Bohemian Region, Czech Republic.

At the Ryirjima mine, Nagano Prefecture, Japan, magnesian kutnahorite was formed principally as fissure fillings. The major vein minerals were deposited during a single period of mineralisation in three stages: quartz, rhodochrosite and finally magnesian kutnahorite (AM 52.1751-1761).

At the Harlech Dome area, Gwynedd, Wales, UK, kutnohorite occurs in an uplifted area of Cambrian rocks associated with spessartine, hematite, magnetite, pyrophanite, quartz and aluminosilicates. The ore-bed is thought to be a sedimentary-exhalative hydrothermal deposit, precipitated on the sea-bed at a considerable distance from the fluid source (MW)

At the the Eldorado Mine, Yankee Boy Basin, Ouray county, Colorado, USA, kutnohorite has been found as tiny crystals and microscopic crystallised tuffs that partially encrust quartz and dolomite (R&M 84.5.423).

At Franklin, New Jersey, USA, kutnahorite has been found in a small veinlet cutting the normal franklinite ore and bordered by a thin layer of rhodochrosite (AM 40.748-760).

Bald Knob, North Carolina, USA, was the source of a sample of kutnohorite from a fine-grained metamorphic rock that equilibrated under middle amphibolite facies conditions at temperatures of 550 to 600oC (AM 72.319-328).

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