Stillwellite-(Ce)

stillwellite-(Ce)

tienshanite

uraninite

sogdianite

Images

Formula: CeBSiO5
Nesosilicate (insular SiO4 groups), borosilicate, cerium-bearing mineral
Specific gravity: 4.57 to 4.60
Hardness: 6½
Streak: White
Colour: Pale violet-grey, light pink, brownish yellow, orange
Solubility: No reaction in acids
Common impurities: Th,Ca,Al
Weakly RADIOACTIVE
Environments

Volcanic igneous environments
Pegmatites
Metamorphic environments
Hydrothermal environments

Stillwellite-(Ce) occurs in garnet-diopside skarn formed between granodiorite and granulite, also in magnetite ore, in pegmatites and hydrothermal veins associated with alkalic rocks and in volcanic ejecta (Dana).

Localities

At the type locality, the Mary Kathleen Mine, Mary Kathleen district, Rosebud Station, Cloncurry Shire, Queensland, Australia, stillwellite-(Ce) occurs in quantity in crystals up to 5 mm in diameter as a major constituent of radioactive ore. It is associated with much allanite and with garnet as a metasomatic replacement of metamorphosed calcareous sediments. Uraninite is dispersed in allanite and stillwellite-(Ce) (AM 41.370-371).

At the Desmont Mine, Monmouth Township, Haliburton County, Ontario, Canada, stillwellite-(Ce) is associated with calcite, monazite-(Ce), bastnäsite, thorite, uranothorite and thorianite (HOM).

At the Dara-i-Pioz Glacier, Districts of Republican Subordination, Tajikistan, stillwellite-(Ce) occurs in alkalic pegmatites in syenite in an alkalic massif. Associated minerals include pyrochlore, tienshanite, sogdianite, thorite, kupletskite-(Cs), reedmergnerite, steacyite, pectolite and quartz (HOM).

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