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 FOV ~ 2 cm. Individual xls ~ 3-4 mm diameter. Via Jean-Yves Lamoureux (found Jan 1988 - at minus 28ºC!). MOB coll. This is classic MSH donnayite-(Y). I don't know if it is from an analyzed find so strictly speaking it is "donnayite group". But here is JY's description of the find: "The famous donnayite pocket opened at the end of 1987. We worked that pocket on January 17, 24, and 31st ,1988, under extreme conditions : minus 28 degrees Celsius on the 24th ! Wine froze in a bottle we had brought... We got out of the pocket soaked to the bones as water continually trickled inside. We were... younger, then! :)" — Photo: Modris Baum · CC0
Donnayite-(Y)
Donnayite-(Y) is a rare-earth carbonate mineral containing the rare-earth metal yttrium. It was first discovered in 1978 at Mont Saint-Hilaire, Quebec. Donnayite was subsequently identified and named after Joseph D. H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and crystallographers, and J. D. H. Donnay was awarded the Roebling Award by the Mineralogical Society of America in 1971 for his emphasis on the importance of optical mineralogy and crystal morphology.
Intro adapted from Wikipedia (CC BY-SA).
Donnayite-(Y) is an IMA-recognized mineral species in the carbonate class, with the chemical formula NaSr₃CaY(CO₃)₆·3H₂O.
It crystallizes in the triclinic crystal system (space group P1). It is a member of the Mckelveyite structural group.
Key properties: Mohs hardness 3; specific gravity 3.3; White streak; Vitreous luster; optically biaxial.
IMA symbol Dna-Y, IMA status: approved, named in 1978.
Found in pegmatite dikes, miarolitic cavities, and interstices in nepheline syenite in an alkaline complex (Mont Saint-Hilaire, Canada).
It is found associated with Ewaldite, mckelveyite-(Y), synchysite, gaidonnayite, arfvedsonite, aegirine, calcite, sphalerite, catapleiite, microcline, analcime, natrolite.
The mineral was named to honor Dr. Joseph Désiré Hubert Donnay (1902–1994), Belgian–American–Canadian crystallographer and his wife Dr. Gabrielle Donnay (1920–1987), American–Canadian mineralogist.