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Formula: CaMn2+(SiO4)
Nesosilicate (insular SiO4 groups), olivine group,
manganese-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 3.407 measured, 3.465 calculated
Hardness: 6
Streak: White
Colour: Bluish-grey, pink, brown or white; may show the alexandrite effect
Luminescence: Not fluorescent under UV
Solubility: The powdered mineral dissolves easily in hydrochloric acid, and the solution produces a gelatinous silica
upon evaporation
Common impurities: Fe,Zn,Pb,Mg
Environments:
Glaucochroite is found in metamorphosed limestone containing
manganese minerals.
Localities
At Anakit Creek, Nizhnyaya Tunguska River Basin, Evenkiysky District, Krasnoyarsk Krai, Russia, glaucochroite occurs in
skarn at the contact between dolerite
and marble
(HOM).
At the Wessels Mine, Joe Morolong Local Municipality, John Taolo Gaetsewe District Municipality, Northern Cape, South Africa,
glaucochroite occurs in calc-silicate rocks with
manganese ores
(HOM).
The type locality, the Franklin Mine, Franklin, Sussex County, New Jersey, USA, is a metamorphosed stratiform
zinc deposit. Euhedral crystals of glaucochroite occur here in a number of
assemblages with nasonite, willemite,
clinohedrite, hardystonite,
diopside and cuspidine. Massive,
coarse-grained, blue glaucochroite occurs with willemite,
franklinite, calcite,
hardystonite, leucophoenicite and
andradite. Massive, fine-grained brown glaucochroite occurs with
esperite, hodgkinsonite,
calcite, willemite,
zincite and franklinite.
Glaucochroite was not observed in association with
tephroite, rhodonite or
wollastonite, all of which occur at Franklin.
At Franklin, glaucochroite is interpreted as forming instead of the commoner assemblage
rhodonite + calcite in local areas with high
activity of water and low activity of carbon dioxide, but under the same temperature and pressure conditions as the deposit as a
whole
(AM 72.423-428).
Glaucochroite from the Franklin Mine - Image
Alteration
bustamite, tephroite and
calcite to glaucochroite and CO2
CaMn2+Si2O6 + Mn2+2(SiO4) + 2CaCO3
⇌ 3CaMn2+(SiO4) + 2CO2
(DHZ 1A p348)
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