Cancrinite - Ca₂Na₆Al₆O₆(CO₃)₂*2H₂O

Found originally in 1839 in the Ural Mountains, it is named after Georg von Cancrin, a Russian minister of finance. Cancrinite is a member of the cancrinite-vishnevite family with the formula Ca₂Na₆Al₆O₆(CO₃)₂*2H₂O. It is classed as a member of the feldspathoid group of minerals. Cancrinite is a rare mineral and occurs in alkaline undersaturated magmatic rocks. it form columnar to needle-shaped crystals but typically granular. In the presence of high CO₂ partial pressures cancrinite con form pseudomorph after Nepheline in alkaline rocks.

Optical properties:
• Form: Columnar or needle-shaped crystals.
• Cleavage: Perpendicular to the long axis.
• Color: Colorless in thin section.
• Extinction: Straight.
• Birefringence: High, from yellow to violet.

Cancrinite pegmatite: Yellow cancrinite with black biotite, nepheline and alkali feldspar. Litchfield, Massachusetts. Photo by W. Cordua, From Wisconsin Geological and Natural History Survey.

Bibliography

• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.

Photo
Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)	Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)	Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)
Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)	Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)	Cancrinite (high interference colors) in a cancrinite-pegmatite from Punkaruaiv, Lovozero, Kola, Russia. XPL image, 10x (Field of view = 2mm)
Cancrinite crystal in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Aegirine crystal rimmed by cancrinite (high interference colros). XPL image, 2x (Field of view = 7mm)	Aegirine crystal rimmed by cancrinite (high interference colros). XPL image, 2x (Field of view = 7mm)
Granular aggregate of Cancrinite crystals in a Nepheline-pegmatite. XPL image, 2x (Field of view = 7mm)	Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Colorless Cancrinite crystals in a Nepheline-pegmatite. PPL image, 10x (Field of view = 2mm)
Granular aggregate of Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)
Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Colorless Cancrinite crystals in a Nepheline-pegmatite. PPL image, 10x (Field of view = 2mm)	Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)
Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Colorless Cancrinite crystals and Aeginrine crystals in a Nepheline-pegmatite. PPL image, 10x (Field of view = 2mm)	Cristalli Cancrinite attorno ad aegirina in una pegmatite a nefelina. Immagine a NX, 10x (lato lungo = 2mm).
Colorless Cancrinite crystals and Aeginrine crystals in a Nepheline-pegmatite. PPL image, 10x (Field of view = 2mm)	Cancrinite crystals on Nepheline. XPL image, 2x (Field of view = 7mm)	Colorless Cancrinite crystals and Aeginrine crystals in a Nepheline-pegmatite. PPL image, 10x (Field of view = 2mm)
Cancrinite crystals in a Nepheline-pegmatite. XPL image, 10x (Field of view = 2mm)	Cancrinite crystals on Nepheline. XPL image, 2x (Field of view = 7mm)	Cancrinite crystals on Nepheline. XPL image, 10x (Field of view = 2mm)
Eudialite (gray) surrounded by sodalite (isotropic) inclusion in a Naujaite. Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)	K-feldspar with sodalite (isotropic) inclusion. Sodalite is surrounded by cancrinite (high interference colors). Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)	K-feldspar with sodalite (isotropic) inclusion. Sodalite is surrounded by cancrinite (high interference colors). Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)
K-feldspar with sodalite (isotropic) inclusion. Sodalite is surrounded by cancrinite (high interference colors). Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)	K-feldspar with sodalite (isotropic) inclusion. Sodalite is surrounded by cancrinite (high interference colors). Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)	K-feldspar with sodalite (isotropic) inclusion. Sodalite is surrounded by cancrinite (high interference colors). Ilímaussaq, Greenland. XPL image, 2x (Field of view = 7mm)
Cancrinite crystals (high interference colors) around sodalite (isotropic). Ilímaussaq, Greenland. XPL image, 10x (Field of view = 2mm)	Cancrinite crystals (high interference colors) around sodalite (isotropic). Ilímaussaq, Greenland. XPL image, 10x (Field of view = 2mm)	Cancrinite crystals (high interference colors). Ilímaussaq, Greenland. XPL image, 10x (Field of view = 2mm)