Cancrinite


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cancrinite

[′kaŋ·krə‚nīt]
(mineralogy)
Na3CaAl3Si3O12CO3(OH)2 A feldspathoid tectosilicate occurring in hexagonal crystals in nepheline syenites, usually in compact or disseminated masses.

Cancrinite

 

(named after the Russian statesman E. F. Cancrin [Kankrin]), the group name of minerals representing a perfect isomorphic series of mixed crystals with the composition nNa6Ca2[AlSi04]6(C03)2⋅2—3H2O (carbonate cancrinite) + mNa6Ca2[AlSi04]6(S04)2⋅2—3H2O (sulfate cancrinite, or vishnevite). The Na:Ca ratio varies; often an impurity of K2O (up to 5 percent) is detected. Cancrinite belongs to the aluminosilicates, with a framework of hexagonal SiO4 rings and A1O4 tetrahedrons connected in vertical six-membered groups. In the ring cavities lie large ions of [SO4]2− or [CO3]2−, formingmolecular intrusive groups with the Ca or 2Na. The mineralcrystallizes in the hexagonal system (crystals are very rare);granular or fine-grained aggregates are common. Cancrinite iscolorless, gray, or pink; sometimes it is light blue (sulfate cancrinite). The prismatic cleavage is perfect. The mineral has a hardness of 5–5.5 on the mineralogical scale and a density of 2, 420–2, 500 kg/m3. In nature it forms from nepheline under the action of sulfate or carbonate postmagmatic solutions. It is found in nepheline syenites and other basic rocks as well as in alkaline pegmatites as a rock-forming mineral.

References in periodicals archive ?
Remnant sodium hydroxide (NaOH) and sodium carbonate ([Na.sub.2]C[O.sub.3]) from the Bayer process plus the formation of desilication products (DSP), sodalite and cancrinite, result in Na being the dominant ion in unamended residue.
This work included major element mineral chemistry for cancrinite, nepheline, and biotite from these rocks.
Nepheline in a mesocratic syenite at Lac Rouge, Quebec (locality 76) is replaced by cancrinite and sodalite, which are subsequently altered to natrolite and thomsonite (Corriveau, 1984).
Ban Invisible Solids, with kihada extract and silver cancrinite, claim to uses this technology to eliminate these odors.
These minerals (natrite, thermonatrite, trona, shortite, sidorenkite, cancrinite group members, etc.) occur in alkaline pegmatites where C[O.sub.2] is a common constituent of gas-liquid inclusions.
Other open questions, to quote the authors, are about the "guarinites", the zeolites, and the cancrinite group minerals.
Associated minerals are: cancrinite, sodalite and natrite (all of which are intergrown with megakalsilite).
Associated minerals are: K-feldspar, nepheline, sodalite, cancrinite, amphibole, pyroxene and other minerals.
Associated minerals are: potassium feldspar, sodalite, cancrinite, pectolite, aegirine, natrite, vililaumite, lomonosovite, chkalovite, nacaphite, fluorcaphite, vitusite, sphalerite and galena.
Furthermore, the similar species cancrinite, practically unknown heretofore in crystals, is present in one unique specimen as a fairly sharp, 2.5-cm, opaque, gray-green crystal, with surrounding smaller ones, in marble.
Surprisingly, only four members of the cancrinite group are found at Monte Somma/Vesuvius, although many others are known from similar volcanic rocks in Italy.