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Formula: ☐Nb2(O,OH)6Cs1-x
Oxide, pyrochlore group,
niobium- and cesium- bearing
mineral
Crystal System: Isometric
Specific gravity: 5.984 calculated
Hardness: 5
Colour: Light brown
Luminescence: Non-fluorescent in UV
Environments
Cesiokenopyrochlore is a rare mineral; it was approved in 2016 and to date (July 2022) has been reported only
from the type locality.
Localities
At the type locality, the Tetezantsio pegmatites, Tetezantsio-Andoabatokely Pegmatite Field, Andrembesoa, Betafo,
Vakinankaratra, Madagascar, cesiokenopyrochlore was discovered in a sample from a rare-element
granitic
pegmatite.
Central Madagascar is characterised by a tectonic structure with a lower unit of
gneiss and an upper unit of
quartzites, schists,
and marbles. Both units are locally intruded by
granitic
pegmatites, which probably formed via fractional
crystallisation of granitic plutons emplaced at relatively shallow
depths. The pegmatites consist of grey
K-feldspar, white to smoky quartz,
white albite, multicoloured
tourmaline, colourless to pink or green
spodumene, and a variety of accessory minerals.
The cesiokenopyrochlore-bearing sample represents a well formed tetrahedral bipyramidal greyish brown
béhierite crystal 7 mm across in a cavity of
quartz-orthoclase aggregate.
Associated minerals include elbaite as pink transparent crystals up to 1 mm,
rynersonite as darkred crystals up to 0.1 mm,
muscovite, xenotime-(Y),
pollucite, zircon, and a
clay mineral, presumably
kaolinite, in a cavity.
Cesiokenopyrochlore is a late-stage mineral forming rough equant crystals up to 0.05 mm overgrowing
béhierite and rynersonite,
which occurs on the surface of the béhierite crystal
(CM 59.1.149–157).
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