Tellurium

tellurium

gold

empressite

emmonsite

Images

Formula: Te
Native element, selenium group
Selen-tellurium is a selenium-bearing variety of tellurium.
Specific gravity: 6.1 to 6.3
Hardness: 2 to 2½
Streak: Grey
Colour: Tin-white
Melting point: 449.51°C
Boiling point: 988°C
Abundance in the earth’s crust: 1 part per billion by weight, 0.2 parts per billion by moles, which makes it one of the rarest stable solid elements (Wiki). Only iridium is rarer.
Common impurities: Se,Fe,Bi,S
Environments

Volcanic fumeroles
Hydrothermal environments

Tellurium is a hydrothermal vein mineral, which may be of both primary and secondary origin, and also a sublimate in volcanic fumaroles. Associated minerals include native gold, sylvanite, empressite, altaite, pyrite, galena, alabandite, baryte, quartz and carbonates (HOM).

Localities

At the Emperor mine, Vatukoula, Viti Levu, Fiji, tellurium occurs as a component of massive ore intimately mixed with sulphides, tellurides and gold, and also as fine crystals up to 4 cm long in quartz cavities (Minrec 39.4.300-301).

At Moctezuma, Moctezuma Municipality, Sonora, Mexico, silver-white native tellurium has been found throughout the Moctezuma orebody in fine-grained masses in veins and as prismatic crystals to several millimeters, usually intimately intergrown with porous networks of minute quartz crystals. Some specimens are partially altered to blackish paratellurite, possibly coloured by submicroscopic inclusions of tellurium. Some of the masses found reached several kilograms in mass (Minrec 55.6.851-852).
Tellurium from Moctezuma - Image

The type locality is the Mariahilf Mine, Faţa Băii, Zlatna, Alba, Romania.
Tellurium from the Mariahilf Mine - Image

At mines in the Cripple Creek mining district, Colorado, USA, tellurite in the oxidised zone with emmonsite and native gold (Minrec 36.2.181).

At the Tintic Mineral District, Utah, USA, although the district is well-known for its rich variety of tellurium minerals, native tellurium is quite rare. A specimen from the Trixie mine has been confirmed by alalysis and a sungle unanalysed specimen showing crystals of what is likely native tellurium has been collected from the North Star mine; it shows perfect cleavage and is directly associated with tellurite. The crystals are very crudely formed, and occur on matrix of quartz (MinRec 55.2.225).
Tellurium from Tintic - Image

Tellurium-bearing minerals include:

Alloys - an alloy is a substance that combines more than one metal or mixes a metal with other non-metallic elements
Sulphides - the sulphide anion is S^2-
Selenides - the selenide anion is Se^2-
Tellurides - the telluride anion is Te^2-
Sulphosalt - A_mB_nX_p: where A is a metal , B usually a semi-metal and X is sulphur, selenium or tellurium
Bismuthides - the bismuthide anion is Bi^3-
Tellurobismuthides - bismuthides where tellurium replaces some bismuth
Oxides - the oxide anion is O^2-
Chlorides - the chloride anion is Cl^-
Sulphates - the sulphate anion is (SO₄)^2-
Thiosulphates - the thiosulphate anion is (S⁶⁺O₃S^2-)^2-, ie a sulphate anion with one O replaced by S
Tellurates - salts of telluric acid H₆Te⁶⁺O₆
Selenites - the selenite anion is (Se⁴⁺O₃)^2-
Tellurites - the tellurite anion is (Te⁴⁺O₃)^2-
Chromates - the chromate anion is (CrO₄)^2-
Phosphates - the phosphate anion is (P⁵⁺O₄)^3-
Arsenates - the arsenate anion is (As⁵⁺O₄)^3-
Vanadates - the vanadate anion is (V⁵⁺O₄)^3-
Phyllosilicates - (Si⁴⁺₂O₅)^2- groups

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