Formula: Na2Zr(Si3O9).2H2O
Cyclosilicate (ring silicate), benitoite group, the monoclinic paramorph of gaidonnayite, which is orthorhombic. Forms a solid solution with calciocatapleiite. Zirconium-bearing mineral.
Specific gravity: 2.65 to 2.9
Hardness: 5½ to 6
Streak: White to pale yellow
Colour:Dark brown, reddish brown, flesh red, yellowish red,colourless, light grey, beige to tan, light yellow, orange, light blue
Common impurities: Ca,Fe

Plutonic igneous environments

Catapleiite occurs in pegmatites, typically as an alteration product of eudialyte, and in syenite and nepheline syenite (Dana, HOM) associated with zircon, leucophanite, rinkite, eudialyte, epididymite, lavenite, astrophyllite, sodalite, natrolite, analcime and aegirine (HOM).

At Strange Lake, Quebec-Labrador, Canada, catapleiite occurs as pseudomorphs after dalyite and vlasovite (Dana).

At Narsarsuk, Greenland, catapleiite has been found in syenite (AM 8.70-72).

At the type locality, Låven, Vestfold, Norway, catapleiite occurs in a nepheline syenite pegmatite, associated with zircon, tritomite-(Ce), mosandrite-(Ce), leucophanite and aegirine (Mindat). The catapleiite-bearing rock is free of eudialyte-eudialyte variety eucolite, but elsewhere at this locality grains of eudialyte are common showing alteration to eudialyte variety eucolite.

At Magnet Cove, Hot Spring county, Arkansas, USA, catapleiite is found in dike rocks made up of feldspar and aegirine, with accessory titanite and secondary natrolite. The catapleiite specimens are free of eudialyte and eudialyte variety eucolite. It appears that eudialyte alters to eudialyte variety eucolite and then to catapleiite, by hydration, with the catapleiite forming at about the same point as the zeolites (AM 8.70-72).

At Buck Hill, Augusta county, Virginia, USA, catapleiite is asssociated with synchysite-(Ce) (R&M 84.4.355).

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