Cinnabar

Cinnabar, sometimes written cinnabarite, is a name applied to red mercury(II) sulfide (HgS), or native vermilion, the common ore of mercury. The name comes from the Greek - "kinnabari" - used by Theophrastus, and was probably applied to several distinct substances. Other sources say the word comes from the Persian zinjifrah, a word of uncertain origin. In Latin it was known as minium, meaning also "red lead" - a word probably borrowed from Iberian (cf. Basque armineá "cinnabar").

Medicinal use
Although cinnabar is known to be highly toxic, it is nevertheless used (as is arsenic) in powdered form mixed with water in traditional Chinese medicine (TCM). Although cinnabar is no longer used in Western medicine, it (along with mercury) historically was used extensively in the West, and TCM practitioners sometimes prescribe it as part of a medicinal mixture, often on the basis of the concept of "using poison to cure poison."