Locality: Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry; Carrière Mont Saint-Hilaire), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada Dimensions: 2.5 cm x 1.7 cm x 1.2 cm 2.5 x 1.7 x 1.2 cm. This is a surprisingly fine and large crystal of remondite from the famous alkaline massif of Mont Saint-Hilaire, Quebec, Canada. Mont Saint-Hilaire is well known for its abundant suite of rare minerals, and some (like this) are very seldom found there. Usually occurring as a micromineral, this remondite thumbnail is one of the few really impressive crystals I have seen, personally, and I think it has a fairly high level of significance. This hexagonal crystal is translucent to gemmy near the termination, where you can see how bright and colorful and superb it is for the species. Formerly in the noted Gilles Haineault Collection, it was last acquired in the mid 1990s by the previous owner. Ex. Hoppel Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Rémondite-(La)
Rémondite-(La) is an IMA-recognized mineral species in the carbonate class, with the chemical formula Na₃(La,Ca,Na)₃(CO₃)₅.
It crystallizes in the monoclinic crystal system (space group P2). It is a member of the Burbankite structural group.
Key properties: Mohs hardness 3; specific gravity 3.5; White streak; Vitreous luster; optically biaxial.
IMA symbol Rém-La, IMA status: approved, named in 1999.
Of late hydrothermal origin, very rare in a small pegmatite in a differentiated alkalic massif.
It is found associated with Cancrisilite, microcline, sodalite, villiaumite, natrolite, pectolite, lomonosovite, barytolamprophyllite, catapleiite, natron, thermonatrite, sazykinaite-(Y).
The name refers to its relation to rémondite-(Ce), and the predominance of lanthanum over other rare-earth elements in the composition.