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Formula: Cu3Se2
Selenide,
berzelianite-umangite group
Crystal System: Tetragonal
Specific gravity: 6.44 to 6.49 measured, 6.590 calculated
Hardness: 3
Streak: Black
Colour: Red, bluish red-black, iridescent violet-blue (tarnished)
Common impurities: Ag
Environments
Umangite is a selenium-bearing mineral found with other selenides in hydrothermal
veins, formed below 112oC. Associated minerals include clausthalite,
tiemannite, berzelianite,
guanajuatite, eucairite,
klockmannite, hessite,
naumannite, chalcomenite,
chalcopyrite, cobaltite,
pyrite, malachite and
calcite
(HOM).
Localities
There are two co-type localities for umangite, Las Asperezas mine, Sierra de Cacho, Villa Castelli, General Lamadrid department,
La Rioja Province, Argentina, and the Trogtal quarries, Lautenthal, Langelsheim, Goslar District, Lower Saxony, Germany.
At Sierra de Cacheuta, Cacheuta, Luján de Cuyo department, Mendoza Province, Argentina, umangite has been found as a
massive ore specimen cut by veinlets of chalcomenite and
malachite
(AM 35.354-356).
At the Tilkerode Mining District, Mansfeld, Mansfeld-Südharz, Saxony-Anhalt, Germany, umangite has been found as finely
disseminated specks in a vein of calcite filling a fracture in dark siliceous rock
(AM 35.354-356).
At the Tsumeb mine, Tsumeb, Oshikoto Region, Namibia, umangite may be part of the
secondary supergene assemblage rather than
a primary hypogene mineral
(R&M 91.6.550)
At the Skrikerum Mine, Valdemarsvik, Östergötland County, Sweden, umangite has been found as finely disseminated specks in
calcite, with minor chalcomenite and
malachite
(AM 35.354-356).
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