Discovered by Baron Franz Joseph Muller von Reichenstein at Subiu, Romania.
Remarks
Silvery white, metallic looking in bulk but usually obtained as dark gray powder. Semi-metal. Burns in air or oxygen. Unaffected by water or HCl but dissolves in HNO3. Used in alloys to improve
machine ability; chemicals, catalysts, electronics.
Diagnostic tests:
Tellurium and tellurides are detected by heating the powdered mineral in a
test tube with 5cc of concentrated H2SO4 acid. The
presence of a reddish-violet color suggests Te. After cooling, addition of
water will cause the color to disappear and a grayish black precipitate of
tellurium will appear.
Open tube test of the powdered mineral oxidizes
tellurium to TeO2 which passes up the tube as a white smoke and
condenses near the heated part as a white coating. The coating can be
fused into a globule which is yellow when hot and white when cold.
Closed tube test of the powdered mineral causes
tellurium to volatize and condense on the hot glass as fused globules
having a metallic luster. Minor amounts of white oxide may be produced
along with the metallic globules.
On charcoal, the blowpipe produces a white sublimate
near the assay somewhat resembling the test for antimony. The sublimate
can be blasted with the blowpipe flame and imparts a pale greenish color
to the flame test.
References
Emsley, J., 1991; THE ELEMENTS : Sec. Ed.,
Clarendon Press, Oxford, 251 p.
(* - Mineral Name Is Not IMA Approved)
(! - New Dana classification added or changed from Danas New Mineralogy)
(? - IMA Discredited Mineral Species Name)
There are 154 minerals with Te in the Mineralogy Database.