Images
Formula: (Ca,Na,☐)2Ta2O6F
Oxide, microlite group,
pyrochlore supergroup,
tantalum-bearing mineral
Crystal System: Isometric
Specific gravity: 6.160 calculated
Hardness: 4 to 5
Streak: White
Colour: Colourless
Luminescence: No fluorescence under UV
Common impurities: Na,Nb,OH
Environments
Localities
At the type locality, the Volta Grande mine, Nazareno, Minas Gerais, Brazil, fluorcalciomicrolite occurs as
an accessory mineral in the granitic
pegmatite that is exceptionally enriched in
lithium and rubidium. Associated
minerals include microcline,
albite, quartz,
muscovite, spodumene,
lepidolite, cassiterite,
tantalite-(Mn),
monazite-(Ce), fluorite,
apatite, beryl,
garnet, epidote,
magnetite, gahnite,
zircon, tourmaline,
bityite,
hydrokenomicrolite and other
microlite-group minerals.
Fluorcalciomicrolite occurs as euhedral, untwinned, octahedral crystals 0.1 to 1.5 mm in size, occasionally
modified by rhombododecahedral faces. The crystals are colourless and translucent with adamantine to resinous lustre.
(MM 77.2989-2996).
Fluorcalciomicrolite from the Volta Grande
Mine - Image
Back to Minerals