Tellurium is an element that is a member of the chalcogen family. It has been used as a coloring agent and in the manufacture of electrical equipment. Exposure may cause nausea, vomiting, and CNS depression. Tellurium is sometimes found in its native (elemental) form, but is more often found as the tellurides of gold (calaverite, krennerite, petzite, sylvanite, and others). Tellurium compounds are the only chemical compounds of gold found in nature, but tellurium itself (unlike gold) is also found combined with other elements (in metallic salts). The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. It is a component of dusts from blast furnace refining of lead. Tellurium is produced mainly in the US, Canada, Peru, and Japan. A brittle silver-white metalloid which looks like tin, tellurium is chemically related to selenium and sulfur. This element is primarily used in alloys and as a semiconductor. Tellurium is a relatively rare element, in the same chemical family as oxygen, sulfur, selenium, and polonium (the chalcogens). When crystalline, tellurium is silvery-white and when it is in its pure state it has a metallic luster. This is a brittle and easily pulverized metalloid. Amorphous tellurium is found by precipitating it from a solution of tellurous or telluric acid (Te(OH)6). Tellurium appears to have no biological role. All tellurium compounds are highly toxic. Inclusion of 1.1% elemental tellurium in the diet of postweanling rats produces a peripheral neuropathy due to a highly synchronous primary demyelination of sciatic nerve. This is caused by Tellurium blocking cholesterol synthesis by inhibiting squalene metabolism. The ingestion of tellurium compounds has been known to be associated with a garlic-like odor of the breath, thus indicating that tellurium is absorbed by the gut, metabolized by tissues, and excreted through routes other than the feces.