Catapleiite - Encyclopedia

    Class : Silicates
    Subclass : Cyclosilicates
    Crystal system : Monoclinic
    Chemistry : Na2ZrSi3O9 2H2O
    Rarity : Uncommon


Catapleiite is a hydrated silicate of nepheline syenites and their pegmatites. It is a secondary mineral resulting from the alteration of eudialyte. Its name comes from the Greek kata (with) and pleios (many), because it is often accompanied by other rare minerals. Catapleiite occurs in thin pseudohexagonal tabular crystals, grouped in rosettes, and frequently twinned. Its color varies : yellow to brown, bluish gray, purplish, sometimes salmon pink. It can exceptionally be used as a gemstone.

Main photo : Catapleiite from Poudrette quarry, Mont Saint-Hilaire, Canada © Kelly Nash

Catapleiite from Poudrette quarry, Mont Saint-Hilaire, Canada © Rock Currier
Catapleiite from Håkestad Quarry, Larvik, Norway © OT. Ljøstad
Catapleiite from Håkestad Quarry, Larvik, Norway © OT. Ljøstad
Catapleiite from Poudrette quarry, Mont Saint-Hilaire, Canada © Modris Baum

Catapleiite in the World

Catapleiite is found in most alkaline syenite massifs. Mont Saint-Hilaire yielded the most extraordinary crystals known: specimens measuring 15 cm by 2.5 cm. Still in Quebec, catapleiite is also known in two quarries opened in small massifs of alkaline syenites in the Montreal metropolitan area (Varennes and Miron). Most of the planet's alkaline massifs, notably those of the Kola Peninsula in Russia (Lovozero, Khibiny), the Los Islands (Guinea), Ilimaussaq (Narssaq, Greenland) and southern Norway (Langesundsfjord ) also provided samples of varying quality.

Catapleiite in France

In France, catapleiite is reported anecdotally in the Velay volcanic area (Haute-Loire) as well as in an intrusive nepheline syenite at Fitou, near Narbonne (Aude).

Twinning and special crystallizations

Polysynthetic twins at 30°, 60° and 90° are known.

Fakes and treatments

No fake identified for this mineral species.



Hardness : 5.5 to 6
Density : 2.65 to 2.9
Fracture : Irregular
Streak : White to yellow



TP : Translucent to transparent
RI : 1.591 to 1.627
Birefringence : 0.036
Optical character : Biaxial +
Pleochroism : Low
Fluorescence : None


Solubility : Nitric acid and hydrochloric acid


Magnetism : None
Radioactivity : None

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