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Formula: PbSe4+O3
Selenite of lead
Crystal System: Monoclinic
Specific gravity: 7.07 measured, 7.12 calculated
Hardness: 3½
Streak: White
Colour: Colourless to white, yellowish white
Environments
Sedimentary environments
Hydrothermal environments
Molybdomenite is a rare species that occurs in the oxidised zone of
selenium-bearing hydrothermal base metal deposits
(HOM).
Localities
At the type locality, the Cacheuta mine, Cerro de Cacheuta, Sierra de Cacheuta, Cacheuta District, Luján de Cuyo
department, Mendoza Province, Argentina, molybdomenite occurs in the oxidised zone of
selenium-bearing hydrothermal base metal deposits, associated with
chalcomenite
(Mindat). It is an alteration product of clausthalite
(Webmin).
Molybdomenite from Cacheuta - Image
At El Dragón mine, Porco Municipality, Antonio Quijarro Province, Potosí, Bolivia, molybdomenite is
associated with chalcomenite,
cobaltomenite, schmiederite,
krut'aite and
alfredopetrovite
(HOM, EJM 28.2.479–484).
This mine is an epithermal deposit consisting of a single selenide vein
with multiple mineralisation stages that is hosted by organic-rich
sandstone and shale.
The major ore mineral is krut'aite, varying in composition to
penroseite. Later solutions rich in
bismuth, lead and
mercury resulted in the crystallisation of minerals such as
clausthalite, petrovicite,
watkinsonite, eldragónite,
grundmannite, hansblockite,
cerromojonite and
nickeltyrrellite. Oxidation produced a wide range of
secondary
selenium-bearing minerals, such as
favreauite,
alfredopetrovite,
franksousaite,
petermegawite,
bernardevansite,
guangyuanite and molybdomenite-P21/c, a
polytype of molybdomenite
(CM 62.4.643-652).
Molybdomenite from El Dragón Mine -
Image
At the Ranwick Mine, Peever Township, Algoma District, Ontario, Canada, molybdomenite occurs as small white to
colourless blades closely associated with clausthalite. Other minerals
reported from this mine include pitchblende,
calcite, hematite,
klockmannite, native selenium,
and malachite
(CM 8.149-158).
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