Cinnabar, with the formula HgS, is the principal ore of mercury.
Cinnabar is a mercury sulfide mineral recognized by its vivid scarlet to brick-red color. It forms mainly in hydrothermal deposits, where hot, mineral-rich fluids move through fractures in rocks at relatively shallow depths. Because cinnabar contains mercury and is often sufficiently concentrated for extraction, it has been the most important natural source of the metal.
The mineral has a long history. Ancient cultures used cinnabar as a red pigment, including in artwork and ceremonial objects. However, mercury compounds and mercury vapor are toxic, so historical pigment use and modern handling require care. Cinnabar should not be treated as a harmless decorative powder.
Cinnabar can be confused with other red minerals, especially red lead or realgar. Its defining chemical identity is mercury sulfide, not merely its color. Mining and processing it can release mercury into the environment.