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Formula: CaMn2+(CO3)2
Anhydrous carbonate, dolomite group, forms a series with
dolomite and with ankerite,
manganese-bearing mineral
Crystal System: Trigonal
Specific gravity: 3.12 measured, 3.15 calculated
Hardness: 3½ to 4
Streak: White
Colour: White, pale rose, pink, light to medium brown
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 kutnohorite 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 the Cuyuna Range, Minnesota, USA, kutnohorite is well-known, forming rounded to botryoidal masses. The
rounded balls are typically less than 1 cm across but a specimen has been found featuring botryoids that measure over 4 cm. Fresh
surfaces are typically a pale beige colour but there is often surface alteration to a darker brown. The most
aesthetic specimens show kutnohorite as rounded balls on goethite
stalactites
(MinRec 56.4.479-481).
Kutnohorite from the Cuyuna Range -
Image
At Franklin, New Jersey, USA, kutnohorite 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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