Weloganite Locality: Francon quarry, Montréal , Québec , Canada ( Locality at mindat.org ) Size: miniature, 5 x 3.8 x 1.8 cm Weloganite An exceedingly well-developed, translucent, and deeply colored 7.5mm weloganite crystal of small size but VERY high quality for the species. This is an extremely rare mineral and good crystals are found only at this locality, near Mont St Hilaire in Quebec (though often they are mislabelled as coming from MSH itself) — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Weloganite
A rare sodium-strontium-zirconium carbonate discovered in 1967, named for Canadian geologist Sir William Logan.
Intro adapted from Wikipedia (CC BY-SA).
Weloganite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Na₂Sr₃Zr(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 3.5; specific gravity 3.2–3.22; White streak; Vitreous luster; refractive index 1.615; optically biaxial.
IMA symbol Wlg, IMA status: approved, named in 1967.
Found in an alkalic sill (Francon quarry, Canada); in association with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada).
It is found associated with Calcite, quartz, dawsonite (Francon quarry, Canada).
The mineral was named to honor William Edmond Logan (1798–1875), first Director of the Canadian Geological Survey.