Cinnabar is a mercury sulfide mineral (HgS). It is one of the few sulfide minerals that lacks a metallic luster (other examples are orpiment & realgar). In its crystalline form, cinnabar has an intense adamantine luster. Massive, fine-grained specimens generally have an earthy luster. Cinnabar has a reddish color reddish streak, 3 different cleavage planes, is quite soft (H = 2 to 2.5), and is heavy for its size (high specific gravity).
Cinnabar principally occurs in some young volcanic rocks and hydrothermal spring deposits. It's a fairly volatile chemical - much of it passes out from volcanic vents into the atmosphere as a gas.
Cinnabar is the most important ore mineral for the element mercury and was long used as a red pigment.
Cinnabar (red) on dolomite (whitish) from Hunan Province, South China (Dwyer Mercer County District Library # 217-110, Celina, Ohio, USA).