Friday, May 6, 2011


I once purchased a specimen labeled as “chalcotrichite, Campbell Shaft, 1800’-2300’ level, Bisbee, AZ”.  In doing some research on this partially-polished specimen, I found some interesting aspects concerning the mineral.  Chalcotrichite is “a variety of cuprite consisting of fibrous sprays or mats of hair-like crystals” (MinDat, 2011).  However, my specimen seems a composition of blood red cuprite (copper oxide, Cu2O), white calcite (CaCO3), and perhaps some native copper (Cu)—no hair like crystals are present. This specimen, collected from the Campbell Shaft or mine near Bisbee, Arizona, is known locally as "campbellite". The mixture is valued as polished specimens or cabochons.  The mine seems a prolific producer of minerals and MinDat has listed 110 different minerals.  Mineralization at the Campbell Mine ore body is largely oxidized copper in Cambrian, Devonian and Mississippian limestones (MinDat, 2011).  At one time the underground mine was a major producer of copper and collectable specimens of azurite, cerussite and malachite.