Host-rocks : Black fetid Namurian bituminous limestones (700 meters thick).
Complex mineralization with three successive primary stages and an important later supergene stage:
1) Pyrite-marcasite-bravoite: Co/Ni sulfarsenides and arsenides in dolomite; associated with acanthite. Cobaltite, Safflorite, gersdorffite.
2) Intermediate stage: Tennantite and sphalerite in quartz/dolomite.
Renierite. Chalcopyrite (with briartite inclusions) and talnakite replacing early assemblage. Tennantite and sphalerite replace cobaltite and safflorite.
3) Cu/Fe sulphides: Chalcopyrite, talnakite and bornite. Chalcocite, djurleite, digenite, covellite.
4) Oxidation sequence: Cementation copper sulfides, native elements and oxidation minerals.
Production and reserves: 200,000 tons extracted.
400,000 tons ore reserves @ 1-3% Ni and 1-3% Co, 1-20% Cu.
Paniagua, A. et al (1988) Bull. Minéral: 111: 383-391.
30 entries listed. 28 valid minerals.
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Locality Updated: Forsythe Mine, Cooksville, Howard Co., Maryland, USAFrom Bill Cordua, 9th Dec 2013 04:44:50