Cancrinite - Encyclopedia
Class : Silicates
Subclass : Tectosilicates
Crystal system : Hexagonal
Chemistry : Na6Ca2Al6Si6O24(CO3)2
Rarity : Uncommon
Cancrinite is a mineral typical of alkaline rocks (nepheline syenites and their pegmatites, ijolites, etc...), in which it can have a primary or secondary origin, by alteration of nepheline. Formerly designating a group, this name is now restricted to carbonate terms, chlorinated terms being called davyne. It was named in honor of Count Egor Frantsevich Kankrin, Russian Minister of Finance. Usually massive, cancrinite is rarely hexagonal prismatic crystals, ending in a flattened pyramid, which does not exceed 2 cm. Its color is variable: colorless, honey yellow, gray, green, blue to gray-blue, reddish. Easily altered, cancrinite transforms into a mixture of zeolite, carbonate and kaolinite.
Main photo: Cancrinite from Caspar Quarry, Ettringen, Germany © Stephan Wolfsried
Cancrinite in the World
Twinning
Twins are rare and lamellar.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 5-6
Density : 2.4 to 2.5
Fracture : Irregular
Streak : White
TP : Transparent to translucent
RI : 1.495 to 1.528
Birefringence : 0.012 to 0.025
Optical character : Uniaxial +/-
Pleochroism : Low
Fluorescence : None
Solubility : Acids
Magnetism : None
Radioactivity : None