Thallium minerals are rare, but a few are known, such as crookesirte and lorandite. The element is widely dispersed, mainly in potassium minerals such as sylvite and pollucite. Thallium is not a rare element it is 10 times more abundant than silver. Thallium amalgam is used in thermometers for low temperature, because it freezes at -58 ☌ (pure mercury freezes at -38 ☌).

It is used for sink-float separation of minerals. Since its electrical conductivity changes with exposure to infrared light, it is used in photocells. Thallium sulphate is still sold in developing countries where it is still permitted as a pesticide, although banned in Western countries. Thallium salts are used as reagents in chemical research. Thallium is used for making low-melting point special glass for highly reflective lenses. A heavy oxide builds up on thallium if left in air, and in the presence of water the hydroxide is formed. When freshly exposed to air, thallium exhibits a metallic lustre, but soon develops a blueish-grey tinge, resembling lead in appearance. Thallium - Tl Chemical properties of thalium - Health effects of thallium - Environmental effects of thallium Separation and Concentration Purification Request.