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Formula: Pb2(UO2)TeO6
Tellurate, uranyl mineral,
lead-bearing mineral
Crystal System: Monoclinic
Specific gravity: 8.496 calculated for the empirical formula
Hardness: 3
Streak: Light orange
Colour: Orange
Luminescence: Not fluorescent under UV
Solubility: In dilute hydrochloric acid, markcooperite immediately decomposes, turning white and opaque, and
then dissolves slowly
Environments
Localities
At the type locality, the Aga Mine, Otto Mountain, Baker, Soda Mountains, Silver Lake Mining District, San Bernardino
County, California, USA, markcooperite is very rare and occurs on fracture surfaces and in small vugs in
quartz veins. Species observed in direct association with markcooperite
include bromine-rich chlorargyrite,
iodargyrite, khinite-4O,
wulfenite and four tellurates,
housleyite, ottoite,
thorneite and timroseite. Other
species identified in the assemblages include acanthite,
anglesite, atacamite,
boleite, brochantite,
burckhardtite, calcite,
caledonite, celestine,
cerussite, chalcopyrite,
chrysocolla, devilline,
diaboleite, eztlite,
fluorite, fornacite,
galena, goethite,
gold, hessite,
jarosite, kuranakhite,
linarite, malachite,
mimetite, mottramite,
munakataite, murdochite,
muscovite, perite,
phosphohedyphane,
plumbojarosite, pyrite,
schieffelinite, vanadinite,
vauquelinite, and two other new minerals,
paratimroseite and
telluroperite.
Markcooperite and most of the other secondary minerals of
the quartz veins are interpreted as having formed from the partial oxidation of
primary sulphides, such as
galena, and tellurides, such as
hessite, during or following
brecciation of the quartz veins.
The uranium may have originated from one or more
primary uranium-bearing
phases (possibly uraninite in the form of inclusions).
Markcooperite crystals are pseudotetragonal prisms ranging from tiny, thin, tapering prisms, less than 5 µm in
length to larger squat prisms to 0.2 mm in length. Most commonly, the mineral occurs as botryoidal aggregates to 0.3 mm
across, which consist of tightly intergrown crystals. Markcooperite is orange and transparent, with a light
orange streak and adamantine lustre
(AM 95.10.1554-1559).
Markcooperite from the Aga Mine - Image
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