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Formula: YNbO4
Multiple oxide containing the rare earth elements niobium and
yttrium, usually metamict, monoclinic
paramorph of tetragonal fergusonite-(Y),
fergusonite group
Crystal System:
Specific gravity: 5.65
Hardness: 5½ to 6½
Colour: yellow
Common impurities: U,Th
Environments
Plutonic igneous environments
Pegmatites
Clinofergusonite-(Y) occurs in granitic rocks
(Webmin).
Localities
At Mount Cervandone in the Western Alps of Italy, an arsenic-rich variety of clinofergusonite-(Y) occurs in cavities
within pegmatite dikes,
associated with quartz, biotite,
K-feldspar, and synchysite-(Ce).
The fergusonite crystallised under amphibolite facies conditions
(AM 95.487-494).
At the type locality, Asht-Sai, Shaidan Massif, Kuraminskii Range, Sughd, Tajikistan, clinofergusonite-(Y) occurs in
microcline granite rocks
(Dana, Webmin).
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