Mcconnellite

mcconnellite

grimaldiite

bracewellite

eskolaite

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Formula: Cu¹⁺CrO₂
Multiple oxide, delafossite group, chromium-bearing mineral
Crystal System: Trigonal
Specific gravity: 5.49 measured, 5.609 calculated
Hardness: 5½
Colour: Deep red
Environments

Sedimentary environments

At the type locality, the Merume river, Kamakusa, Potaro-Siparuni Region, Guyana, mcconnellite occurs in alluvial gravel as well developed tabular deep red rhombohedral crystals up to 1 mm in size and with perfect cleavage, found in vugs as inseparable intergrowths (polycrystals) with grimaldiite. Other associated minerals include bracewellite, eskolaite and guyanaite (U.S. Geological Survey Professional Paper 887: 1–29, Mindat, HOM, Dana).

At unnamed marble quarries, Tulul al Hammam, Siwaga, Lisdan-Siwaga Fault, Hashem region, Daba-Siwaqa complex, Transjordan Plateau, Amman Governorate, Jordan, mcconnellite and ellinaite were found in varicoloured marbles of the pyrometamorphic Hatrurim Complex (MM 85.3.387–397).

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