Fergusonite-(Y)-β

minerals

synchysite

fergusonite

microcline

Formula: YNbO4
Multiple oxide containing the rare earth elements niobium Nb and yttrium Y, usually metamict, monoclinic paramorph of fergusonite-(Y), which is tetragonal, fergusonite group
Specific gravity: 5.65
Hardness: 5½ to 6½
Colour: yellow
Common impurities: U,Th
Environments

Plutonic igneous environments
Pegmatites

Fergusonite-(Y)-β occurs in granitic rocks (Webmin).

Localities

At Mount Cervandone in the Western Alps of Italy, an arsenic-rich variety of fergusonite-(Y)-β 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, fergusonite-(Y)-β occurs in microcline granite rocks (Dana, Webmin).

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