This mineral forms as thick tabular, rhombohedral, and prismatic crystals, which are commonly twinned. It also occurs in massive, encrusting, or granular habits. The color is typically brownish red or scarlet.
The streak is scarlet. Cinnabar is transparent to opaque and has an adamantine, submetallic, or dull luster.
FORMATION Forms cinnabar with realgar and pyrite around volcanic vents and hot springs.
Other associated minerals include native mercury, marcasite, opal, quartz, stibnite, and calcite. It may also occur in mineral veins and in sedimentary rocks associated with recent volcanic activity.
TESTS Does not alter when exposed to the atmosphere.
Group: SULFIDES
Composition: HgS
Hardness: 2½
SG: 8.08
Cleavage: Perfect prismatic
Fracture: Conchoidal to uneven
