Abstract

Aluminum-rich chromium-dravite is found in association with bright green tremolite (0.40 wt.% Cr2O3), quartz, phlogopite, and fluorapatite in talc – tremolite – cummingtonite schist at the #1 mine at Balmat in the Adirondack Lowlands, St. Lawrence County, New York. The mineral occurs as small (up to 0.5 mm) dark green crystals in quartz, tremolite or along tremolite cleavages and contacts. The assemblage Al-rich chromium-dravite + tremolite + quartz ± phlogopite ± talc ± fluorapatite probably formed during regional metamorphism at peak metamorphic conditions of 6.5 ± 1 kbar and 650 ± 30°C. The assemblage most likely resulted through the interaction of hydrothermal-metamorphic fluids with a metasomatically altered mafic-ultramafic protolith from within the Upper Marble Formation.

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