Petarasite Locality: Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry), Mont Saint-Hilaire , Rouville RCM, Montérégie , Québec , Canada ( Locality at mindat.org ) Size: 4.0 x 2.9 x 2.7 cm. An incredibly large, sharp crystal of this very rare species found in only a few small pockets over all the years at Mont Saint-Hilaire. It was in fact self-collected by the incredibly persistent collecting couple, Marcelle and Charles Weber, and remained in their collection since 1980. At approx 1.5 x 1 cm, this is large for the species. Moreover, it displays really nicely atop contrasting matrix. It has a lustrous, red-brown color to it. It is terminated on the left end, contacted on the right. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Petarasite
Petarasite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₅Zr₂Si₆O₁₈(Cl,OH)·2H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/m).
Key properties: Mohs hardness 5–5.5; specific gravity 2.88; White streak; Vitreous luster; optically biaxial.
IMA symbol Pra, IMA status: approved, named in 1979.
Found in a biotite-microcline xenolith and in pegmatitic veins in a nepheline syenite in an intrusive alkalic gabbro-syenite complex.
It is found associated with Biotite, microcline, catapleiite, apatite, zircon, natrolite, nepheline, cancrinite, eudialyte, aegirine, mosandrite, analcime, ancylite, fluorite, sodalite.
In honor of Dr. Peter Tarasoff, amateur mineralogist, Dollard-des-Ormeaux, Quebec, Canada.