Crookesite is a selenide mineral composed of copper and selenium with thallium or silver. It is a mixture of Cu₇TlSe₄ and Cu₇AgSe₄. It is formed by precipitation from hydrothermal fluids. The selenide ion is Se2-. A selenide is a chemical compound in which selenium serves as a anion with oxidation number of -2, much as sulfur does in a sulfide. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11 , 4, d Density, Hardness 8920 kg/m3, 3. ... General Name, Symbol, Number selenium, Se, 34 Series nonmetals Group, Period, Block 16 (VIA), 4, p Density, Hardness 4790 kg/m3(300K), 2 Appearance grey, metallic lustre Atomic properties Atomic weight 78. ... General Name, Symbol, Number Thallium, Tl, 81 Chemical series Poor metals Group, Period, Block 13 (IIIA), 6, p Density, Hardness 11. ... General Name, Symbol, Number silver, Ag, 47 Chemical series Transition metals Group, Period, Block 11, 5, d Density, Hardness 10490 kg/m3, 2. ... Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ...

It is named after Sir William Crookes, the discoverer of the element thallium. Sir William Crookes (June 17, 1832 – April 4, 1919) was an English chemist and physicist. ...

External links

• web mineral site
• mindat mineral data