Crookesite Crookesite Crookesite is a selenide mineral composed of copper and selenium with variable thallium and silver. Its chemical formula is reported either as Cu(Tl,Ag)Se or (Cu,Tl,Ag)Se. It is formed by precipitation from hydrothermal fluids, and contains by mass: 16.3% Tl, 47.3% Cu, 2.9% Ag, and 33.6% Se. Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the tetragonal system. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 6.9. It was discovered in 1866 in Skrikerum, Sweden and named for Sir William Crookes (1832–1919), the discoverer of the element thallium.
Naming of chemical elements names can refer to: Chemical elements are sometimes named after people, especially the synthetic elements discovered (created) after ca. 1940. However, very few are named after their discoverers, and even fewer are named after living people. The element seaborgium is named after Glenn Seaborg, who was alive at the time; and oganesson is named after Yuri Oganessian (still living ). Many of the transuranic elements are named after recipients of the Nobel Prize, including: Transuranic elements named in honour of scientists who did not receive the prize include: The transuranic element americium is indirectly named (via the continents The Americas)