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Formula: (Na,Pb,Ca,REE,U)2Nb2O6F
Oxide, pyrochlore group,
uranium-
and niobium- bearing mineral
Crystal System: Isometric
Specific gravity: 5.275 calculated
Hardness: 4 to 4½
Streak: Light yellow
Colour: Brownish yellow to reddish orange
Luminescence: Non-fluorescent under UV
Environments
Localities
At the type locality, the Boziguoer intrusion, Baicheng county, Aksu Prefecture, Xinjiang, China,
fluornatropyrochlore was found in the alkaline intrusive
granitic rocks. The igneous intrusion played an important role in
niobium-tantalum mineralisation and
contributed to the high content of rubidium,
uranium, thorium,
zirconium and rare earth elements. The Boziguoer rock
is a niobium-,
tantalum- and rare-earth-element-rich plutonic rock.
There are different mineral parageneses in the eastern and western mine areas. As accessory minerals,
xenotime-(Y),
chevkinite-(Ce) and
fergusonite-(Y) are mainly found in
aegirine granite in the
western mining area, and thorite and
columbite-(Fe) are mainly found in a
monzogranite in the eastern mining area. However,
fluornatropyrochlore, together with astrophyllite,
zircon, fluorite,
fluocerite-(Ce) and monazite,
are commonly found in both of the mining areas. Other common minerals are
microcline, albite,
anorthite, quartz,
aegirine, a sodic amphibole,
biotite, rutile,
fluorite and members of the
columbite-(Fe)-columbite-(Mn)
series.
Fluornatropyrochlore mainly occurs in a
niobium-tantalum-rich alkali
syenite deposit
(CM 53.455-460).
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