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Formula: Cu(Se4+O3).2H2O
Selenite, orthorhombic paramorph
of monoclinic clinochalcomenite
Crystal System: Orthorhombic
Specific gravity: 3.35 measured, 3.4 calculated
Hardness: 2 to 2½
Streak: Light blue
Colour: Intense blue, pale blue in transmitted light
Solubility: Soluble in acids
Environments
Chalcomenite is a rare secondary mineral in oxidised
copper-selenium bearing deposits
(Mindat, HOM).
Localities
At the type locality, Cerro de Cacheuta, Sierra de Cacheuta, Cacheuta, Luján de Cuyo department, Mendoza Province,
Argentina, chalcomenite
is associated with umangite,
clausthalite,
molybdomenite and
schmiederite
(HOM).
At the El Dragón mine, Antonio Quijarro Province, Potosí, Bolivia, chalcomenite is associated with
allophane, felsőbányaite,
malachite and clinochalcomenite
(HOM).
At the Hiaco mine, Pakajake Canyon, Chayanta Province, Potosí, Bolivia, chalcomenite is associated with
penroseite, cobaltomenite and
molybdomenite
(HOM).
At the Musonoi Mine, Kolwezi, Kolwezi mining district, Lualaba, DR Congo (Zaire), chalcomenite is associated with
guilleminite, derriksite and other selenites
(Dana).
At cliffs near Ballybunnion, Kerry County, Munster, Ireland, a hand-sized specimen of carbon-rich black shale
has been found with two fractures
hosting isolated crystals, radiating groups and crude dendrites of bright blue chalcomenite. A white to pale green encrustation of
mandarinoite surrounds most of the chalcomenite, completely replacing some crystals.
There are a few other minerals on the specimen, tiny crystalline aggregates of a sodium
iron sulphate, possibly sideronatrite,
metasideronatrite, jarosite or
natrojarosite, and extremely small pale green spheroidal aggregates of a
copper chloride, most likely atacamite, and efflorescences of
what is probably gypsum
(JRS 19.35-39).
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