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Formula: (Mn,Mg)MgSi2O6
Inosilicate, orthopyroxene subgroup,
pyroxene group,
manganese-bearing mineral,
paramorph of kanoite
Crystal System: Orthorhombic
Specific gravity: 3.36 measured, 3.403 calculated
Hardness: 5 to 6
Colour: Pale buff, yellow-orange; faint pink in thin section
Common impurities: Al,Fe,Ca,Na
Environments
Localities
At the type locality, the Empire State No. 4 Mine, Balmat, Fowler, St. Lawrence County, New York, donpeacorite
occurs in manganese-rich siliceous
marbles, which are common throughout the Adirondack Lowlands and were
metamorphosed to the upper amphibolite facies during
the billion-year-old Grenville orogeny.
Donpeacorite occurs as l to 3 mm interlocking grains making up over 50 percent of a massive coarse-grained
yellow-orange rock. The ground mass consists mainly of a fibrous
amphibole, with minor
tourmaline, ferrian braunite,
manganese-bearing dolomite,
hedyphane-like apatite and
anhydrite. The fibrous
amphibole, which
is closely associated with the donpeacorite, is faint orange in hand specimen and colourless in thin-section.
The donpeacorite is pale buff in hand specimen and faintly pink in thin section
(AM 69.472-480).
Donpeacorite from the Empire State No. 4 Mine -
Image
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