Images
Formula: ThO2
Oxide, uraninite group, forms a series with
uraninite
Crystal System:
Specific gravity: 9.7 to 9.8
Hardness: 6½ to 7
Streak: Grey, grey-green to black
Colour: Black, brownish black, dark grey, dark reddish brown
Magnetism: Diamagnetic
Common impurities: U,Ce,La,Pb,TR
RADIOACTIVE
Environments
Pegmatites
Carbonatites
Metamorphic environments
Thorianite is an accessory mineral in granite
pegmatites, and more rarely in
carbonatites or
serpentinite; it is commonly detrital in heavy mineral concentrates
(HOM).
Localities
At the Andoloabo thorianite deposit, Belafa area, Maromby, Amboasary Sud, Anosy, Madagascar, thorianite is
associated with phlogopite, diopside
and spinel
(HOM).
At the Turja peninsula, White Sea, Russia, thorianite occurs with
pyrochlore as an accessory in the original
calcite-diopside-hornblende
and
calcite-garnet-vesuvianite
rocks.
As a rule, the
calcite-diopside-hornblende
rocks are medium to fine-grained aggregates of zeolites,
calcite and apatite, including short
prismatic and xenomorphic grains of diopside.
Perovskite occurs as an accessory mineral. Evenly scattered in this
polymineralic aggregate are rounded grains of magnetite and large (1-3 cm)
poikilitic crystals of hornblende.
The calcite-garnet-vesuvianite
rocks are composed of a fine-grained
garnet-vesuvianite-phlogopite-calcite
aggegate in which megacrysts( l-2 cm) of garnet and
magnetite are uniformly distributed.
Calcite also occurs in separate pockets.
Perovskite is an accessory mineral
(AM 59.378-380).
At the type locality, Balangoda, Ratnapura District, Sabaragamuwa Province, Sri Lanka, thorianite is an accessory
mineral in granite
pegmatites
(Mindat).
Associated minerals include thorite,
zircon, ilmenite,
cassiterite and allanite
(HOM).
At Rose Road, Pitcairn, St. Lawrence county, New York, USA, thorianite mineralisation fluoresces brilliant
green both from pieces of the original pod and from patchy coatings on the surfaces of other minerals that were down
slope from the pod in fractured areas or as loose pieces in the scree
(R&M 97.5.442).
Back to Minerals