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Formula: (Ca,Na)2(Nb,Ti)2O6F
Oxide, pyrochlore group,
pyrochlore supergroup,
niobium- and titanium-
bearing mineral
Crystal system: Isometric
Specific gravity: 4.34 calculated
Hardness: 5
Streak: Light yellow
Colour: Brownish yellow to reddish orange
Solubility: Insoluble in hydrochloric or nitric acid
Environments
Fluorcalciopyrochlore is a relatively new mineral, approved in 2013.
Localities
The type locality is the Bayan Obo deposit, Bayan Obo, Bayan Obo mining district, Baotou City, Inner Mongolia, China.
The deposit is the world’s largest known rare earth
element ore deposit and a major iron and
niobium producer as well. Fluorcalciopyrochlore occurs in
carbonatites, disseminated as fine grains and veinlets or
scattered between dolomite crystals. The mineral is often euhedral or
subhedral, associated with dolomite and
calcite, with all three minerals crystallising at the same time. Other
associated minerals are aegirine,
riebeckite, diopside,
fluorite, baryte,
phlogopite,
britholite-(Ce),
bastnäsite-(Ce), zircon,
magnetite, pyrite,
fersmite, columbite-(Fe),
monazite-(Ce) and rutile.
While most often fluorcalciopyrochlore occurs as subhedral or allotriomorphic grains, it sometimes forms as
octahedra, dodecahedra and cubes, or combinations thereof. Crystals generally range in size from 0.01 to 0.3 mm. It
is brownish yellow to reddish orange in colour with a light yellow streak, translucent to transparent with an
adamantine to greasy lustre on fractured surfaces and a conchoidal fracture
(CM 54.5.1285-1291).
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