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Formula: CrO(OH)
Hydroxide, diaspore group,
paramorph of grimaldiite
and guyanaite, chromium-bearing
mineral
Crystal System: Orthorhombic
Specific gravity: 4.45 to 4.48 measured, 4.28 calculated
Hardness: 5½ to 6½
Streak: Dark brown
Colour: Deep red to black
Environments
Sedimentary environments
Hydrothermal environments
Localities
At the type locality, the Merume river, Kamakusa, Potaro-Siparuni Region, Guyana, bracewellite occurs in an
alluvial placer deposit, in fine-grained intergrowth with other chromium
oxide-hydroxide minerals. Associated minerals
include quartz, pyrophyllite,
mcconnellite, guyanaite,
grimaldiite, gold,
gahnite and eskolaite
(Mindat).
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