What is "tiemannite"

n. (context mineralogy English) An isometric-hextetrahedral grayish white mineral containing mercury and selenium.

Tiemannite is a mineral, mercury selenide, formula HgSe. It occurs in hydrothermal veins associated with other selenides, or other mercury minerals such as cinnabar, and often with calcite. Discovered in 1855 in Germany, it is named after Johann Carl Wilhelm Tiemann (1848–1899).