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Formula: FeCe(MoO4)3.3H2O
Hydrated molybdate,
cerium-bearing mineral
Crystal system: Trigonal
Specific gravity: 3.834 calculated
Hardness: 4 to 4½
Streak: Yellow
Colour: Red or pale brown
Luminescence: Not fluorescent under UV
Environments
Plutonic igneous environments
Hydrothermal environments
Localities
At the type locality, Punta de Su Seinargiu, Sarroch, Metropolitan City of Cagliari, Sardinia, Italy,
tancaite-(Ce) occurs within cavities in the quartz veins which cut
the granite. It is a
secondary mineral formed in the oxidation zone of a
sulphide ore vein. Associated minerals are quartz,
muscovite, molybdenite,
pyrite and a
mendozavilite-like phase. Tancaite-(Ce) is red or pale
brown in colour, with a vitreous to adamantine lustre
(EJM 32.347–354).
It occurs as small truncated octahedra up to 0.2 mm in size
(Mindat).
Tancaite-(Ce) from Punta de Su Seinargiu -
Image
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