Abstract
A jet black to brownish pitch-like material rich in copper is frequently encountered among the supergene minerals of copper deposits. It has a conchoidal fracture and when occurring in large enough pieces, closely resembles obsidian or even anthracite coal. It seems to vary in hardness from less than 3 to about 4 and is sometimes very brittle. It often grades into portions that are more or less sooty, thus increasing its resemblance to coal. It is frequently associated with copper oxide (cuprite) with comparatively small amounts or even no other copper minerals closely associated with it. (Analysis No. 1). Such specimens seem to possess the maximum hardness if we except those varieties which contain considerable chalcedony. In other cases, and more characteristically perhaps, it is associated with blue and greenish chryso-colla, malachite and limonitic material. Sometimes the mass appears rather streaked with the black, brown, blue and greenish material intermingled. Specimens of copper pitch are mostly opaque even in thin slivers though one sample from Katanga, Belgian Congo, while black in the hand specimen appeared quite transparent on the thin edges. This specimen seemed to grade into chrysocolla, perhaps with an excess of silica.
