I found this specimen, of all places, for sale at the Munich show. Things get around, as they say! This extremely rich, large, cabinet specimen is one of the prettier Bristol chalcocites around, for the rich crystallization set starkly upon contrasting quartz crystalline matrix. The crystallized matrix is uncommon, and really offsets the matte black chalcocite nicely. The clusters are very 3-dimensional and dramatic, upon it. Also, small green flecks of malachite or bornite perhaps, seem to be present. Commercial mining began in 1837 and carried on until 1953 (according to Mindat.org) - this mine was a hugely important US resource through the Civil War years and beyond, and collectors lament its closing.