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Formula: Fe3+3Bi5O9(Te4+O3)(Te6+O4)2.9H2O
Tellurite, bismuth-bearing
mineral
Crystal System: Tetragonal or Hexagonal
Specific gravity: 5.59 measured
Hardness: 3
Streak: Yellow
Colour: Yellow, orange to brown, yellow-brown
Solubility: Fuses easily to a red glass and begins to evolve TeO2 shortly after the loss of water. It
is readily soluble in cold 16% hydrochloric acid or 10% nitric acid
Environments
Yecoraite occurs in fractures in a quartz vein emplaced in
quartz monzonite, an
oxidation product of tetradymite and
pyrite. Associated minerals include
tetradymite, pyrite,
chalcopyrite, quartz and
iron oxides
(HOM).
Localities
At the type locality, the San Martín de Porres Mine, Yécora, Yécora Municipality, Sonora, Mexico, yecoraite
is found in quartz veins that cut
granite, as pitchy or resinous masses intimately associated with
tetradymite, often penetrating along cleavage. Other associated
phases include goethite,
chalcopyrite, pyrite, and
two unidentified tellurites-tellurates of bismuth and
iron. No crystals were found (AM 71.1547). Yecoraite is an
oxidation product of tetradymite and
pyrite
(Mindat).
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