Item# Crocoite

Scientific Name: Lead chromate

Group: Chromates

Chemical composition: PbCrO4

Colors: Orange, red

Hardness: 2.5 to 3

Formation: Monoclinic crystal; prismatic form; cleavage distinct in one direction; conchoidal to uneven, brittle fracture; vitreous luster; transparent to translucent

Principal Sources: Tasmania; Russia; Germany; California, USA

Special Notes: Crocoite is sometimes used as a paint, being identical in composition with the artificial product chrome yellow. It takes its name from the Greek for "saffron" after its color. The relative rarity of crocoite is connected with specific conditions required for its formation: an oxidation zone of lead ore bed and presence of ultramafic rocks serving as the source of chromium (in chromite). Oxidation of Cr3+ into CrO42- (from chromite) and decomposition of galena (or other primary lead minerals) are required for crocoite formation.