Leonard James Spencer, 1911 Encyclopædia Britannica, Volume 6… (1911)
“ A mineral known as pitchy copper-ore (Ger. Kupferpecherz) , and of some importance as an ore of copper, is usually classed as a variety of chrysocolla containing much admixed limonite. It is dark brown to black in colour, with a dull to glassy or resinous lustre, and resembles pitch in appearance. In thin sections it is translucent and optically isotropic, and recent examinations seem to prove that it is a homogeneous mineral and not a mechanical mixture of chrysocolla and limonite. ”
