Sorosilicate (Si2O7 groups), chevkinite group
Specific gravity: 4.4 to 4.9
Hardness: 5 to 6
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
Chevkinite 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).
At the type locality, Pit No. 17, Ilmen Mountains, Chelyabinsk Oblast, Russia, chevkinite 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 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.
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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