The commonest mercury mineral, HgS; sp. gr. 8.0–8.2; hardness 2.0–2.5; trigonal; scarlet-red to brownish-red; vermilion streak; adamantine lustre; crystals rhombohedral or thick, tabular plates, but can occur massive or granular; cleavage perfect prismatic {1011⁻} sedimentary rocks, in fractures in areas of volcanic activity, and around hot springs, associated with pyrite, stibnite, and realgar. It is the only major ore of mercury.