Cancrinite Locality: Dennis Hill locality (Litchfield sodalite locality), Litchfield, Kennebec County, Maine, USA Description: Yellow cancrinite in nepheline sy — Photo: Douglas Watts · CC BY 3.0
Cancrinite
A complex sodium-calcium carbonate-silicate of the feldspathoid group — the framework silicates poorer in silica than feldspars.
Intro adapted from Wikipedia (CC BY-SA).
Cancrinite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Na,Ca, )₈(Al₆Si₆)O₂₄(CO₃,SO₄)₂·2H₂O.
It crystallizes in the hexagonal crystal system (space group P6_3). It is a member of the Cancrinite structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.42–2.51; typically yellow or white or gray or blue or green or orange; White streak; Vitreous, pearly, or greasy luster; refractive index 1.508; optically uniaxial.
IMA symbol Ccn, grandfathered status — known before the IMA’s founding, named in 1833.
Found as a primary mineral in some alkalic igneous rocks, including pegmatites in nepheline syenites. It is also found as an alteration product of nepheline.
It is found associated with Nepheline, sodalite, natrolite, orthoclase, monticellite, titanian andradite, zircon.
The name refers to Count Egor Frantsevich Kankrin (Georg Cancrin) (1774–1845), German-Russian Minister of Finance of Russia.
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