GREENOCKITE, a rare mineral composed of cadmium sul phide, CdS, occurring as small, brilliant, honey-yellow crystals or as a canary-yellow powder. Crystals are hexagonal with hemimor phic development, being differently terminated at the two ends; they are translucent to transparent, and have an adamantine to resinous lustre; hardness 3-3 i ; specific gravity 4.9. Crystals have been found only at one or two places in the neighbourhood of Glasgow, where they occur singly on prehnite in the amygdaloidal cavities of basaltic igneous rocks. At all other localities the min eral is represented only as a powder dusted over the surface of zinc minerals, especially blende and calamine, which contain a small amount of cadmium replacing zinc.