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Formula: Fe3+2(Se4+O3)3.6H2O
Selenite
Crystal System: Monoclinic
Specific gravity: 2.93 measured, 3.04 calculated
Hardness: 2½
Streak: Very pale green
Colour: Pale yellow green
Environments
Mandarinoite is a secondary mineral found in the
oxidised zones of selenium and iron
bearing deposits
(Mindat).
Localities
At the El Dragón mine, Antonio Quijarro Province, Potosí, Bolivia, mandarinoite occurs with
chalcomenite on krut'aite
(Dana, HOM).
At the type locality, the Virgen de Surumi mine, Pakajake Canyon, Chayanta Province, Potosí, Bolivia, mandarinoite
probably formed by the simultaneous oxidation of penroseite and
pyrite in a selenium-rich ore deposit.
Associated minerals include penroseite,
siderite, goethite and
quartz
(HOM).
At the Skouriotissa Mine, Skouriotissa, Nicosia District, Cyprus, mandarinoite occurs on
quartz
(Dana).
At the El Plomo Mine, Ojojona, Francisco Morazán Department, Honduras, mandarinoite occurs with
poughite
(HOM).
From the cliffs near Ballybunnion, Kerry County, Munster, Ireland, mandarinoite has been identified as minute
white to pale green crystals replacing chalcomenite, on black
shale. The mandarinoite was identified at the Natural History
Museum in London on a hand-sized block of carbon-rich black shale with
sharp fractures and bedding planes. Two fractures host isolated crystals, radiating groups and crude dendrites of
bright blue chalcomenite. A white encrustation of mandarinoite
surrounds most of the chalcomenite and completely replaces some crystals.
There are very few other minerals on the specimen, but the possible presence of
sideronatrite,
metasideronatrite, jarosite,
natrojarosite, atacamite and
gypsum has been noted
(JRS 19.35-39).
At the De Lamar Mine, De Lamar Mining District, Owyhee county, Idaho, USA, the mineralisation of the mine occurs in
siliceous veins in a quartz-feldspar
rhyolite porphyry.
Deposition of the primary minerals occurred at shallow depths
from sodium chloride solutions. Primary minerals, in order of
decreasing abundance, include pyrite,
marcasite, naumannite,
aguilarite, acanthite,
pyrargyrite, miargyrite,
chalcopyrite, sphalerite and
gold.
Secondary minerals include
goethite, chlorargyrite,
mandarinoite, silver, covellite
and copper. The mandarinoite occurs in narrow, open veinlets as pale
lime-green crystals up to 0.5 mm long, and as isolated, radiating rosette-like clusters up to 1.5 mm in diameter, perched
on drusy quartz. The crystals are usually bright, shiny and transparent, but
some have dull, frosted surfaces. Chlorargyrite is found on both the
quartz and the mandarinoite crystals, suggesting that it crystallised
later than either of these
(CM 16.605-609).
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