black earth (pigment) en

A class of pigments where a variety of both inorganic and organic compounds may be present. Historically, comparatively little is known about which materials were used as black pigments, and in treatises on painting technique, the terms black earth, black chalk and black stone were used interchangeably, whether discussing black pigments or drawing materials. In current technical literature, black earth is generally assumed to be a black shale or chalk, but other bituminous materials and minerals have been identified.