Chevkinite-(Ce)

chevkinite-(Ce)

aegirine

titanite

allanite

Formula: Ce4(Ti,Fe2+,Fe3+)5O8(Si2O7)2
Sorosilicate (Si2O7 groups), chevkinite group
Crystal System: Monoclinic
Specific gravity: 4.53 to 4.67 measured, 4.99 calculated
Hardness: 5 to 6
Streak: Grey-brown
Colour: Black, dark brown, dark reddish brown
Solubility: Soluble in hydrochloric and nitric acids, HF and AR, but not in bases
Common impurities: Ca,Nb,Mg,Th,Sr,Zr
Weakly RADIOACTIVE
Environments

Igneous environments
Pegmatites
Carbonatites

Chevkinite-(Ce) occurs as a minor accessory mineral in volcanic ash beds and rhyolite, but more commonly as an accessory mineral in alkaline or peralkaline granite, granite pegmatites, nepheline syenite, syenite and syenite pegmatites; rarely in fenite and carbonatites (Dana, HOM, Webmin).

Localities

At the type locality, Pit No. 17, Ilmen Mountains, Chelyabinsk Oblast, Russia, chevkinite-(Ce) occurs as crystals up to 5 cm in aegirine - quartz - feldspar pegmatites associated with titanite, amphiboles, allanite-(Ce) and aegirine (Mindat).

In the Aquarius Mountains, Mohave county, Arizona, USA, chevkinite-(Ce) is associated with titanite, monazite, apatite, cronstedtite and quartz (HOM).

At the Wausau Intrusive Complex, Marathon county, Wisconsin, USA, there have been three finds of chevkinite-(Ce).
The first, near the contact with a large quartzite xenolith, occurred in small pegmatoidal veins and clots largely composed of feldspar, quartz, amphiboles, zircon and grains of an altered chevkinite-group mineral. Accessory minerals include apatite, monazite, and allanite-(Ce).
The second find was in a quarry where the syenite was cut by small pegmatites containing small crystals of a chevkinite-group mineral associated with quartz, microcline, albite, biotite, aegirine, ilmenite, probable rhabdophane-(Ce), xenotime-(Y), amphiboles, fayalite, a euxenite-like oxide and magnetite.
The third find was in heavy mineral separates prepared from a fine-grained mafic dike cutting granite. Associated minerals include amphiboles, biotite, chlorite, fluorapatite and very rare columbite-group and monazite-group species (R&M 87.2.172-173).

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