Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. 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 C. W. Tiemann (1848-1899). Mercury selenide (HgSe) is a chemical compound of mercury and selenium. It is a grey-black crystalline solid semi-metal with a sphalerite structure. The lattice constant is 0.608 nm. Mercury selenide can also refer to the following chemical compounds: HgSe2 and HgSe8. HgSe is strictly mercury(II) selenide. HgSe occurs naturally as the mineral Tiemannite. Along with other II-VI compounds, colloidal nanocrystals of HgSe can be formed.