Weloganite: Francon Quarry, Quebec, Canada (0.37). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Truly a collector’s gem, weloganite is very rare and seldom cut. This stone can show pale yellow colors.
Weloganite: Francon Quarry, Quebec, Canada (0.37). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Truly a collector’s gem, weloganite is very rare and seldom cut. This stone can show pale yellow colors.
| Data | Value |
|---|---|
| Name | Weloganite |
| Formula | Na2Sr3Zr(CO3)6 · 3H2O |
| Colors | White, lemon yellow, amber, colorless. Crystals may be zoned. |
| Fracture | Conchoidal |
| Hardness | 3.5 |
| Cleavage | Perfect |
| Crystallography | Triclinic; crystals pseudo-hexagonal, barrel shaped with heavy striations on prism faces, also grooved due to oscillatory growth. Crystals distinctive, terminated by pedion or pyramids. Also massive. |
| Refractive Index | 1.558-1.648 |
| Birefringence | 0.090 |
| Luminescence Present | No |
| Absorption Spectrum | Not diagnostic |
| Pleochroism | None |
| Optics | a = 1.558; β = 1.646; γ = 1.648. Biaxial (-). Some stones may appear uniaxial. 2V about 15º. |
| Optic Sign | Biaxial - |
| Luster | Vitreous |
| Specific Gravity | 3.20 |
| Transparency | Transparent to translucent |
| Phenomena | May show triboluminescence |
| Etymology | For William E. Logan, first director of the Geological Survey of Canada. |
| Occurrence | In alkalic sill intruding in limestone |
Weloganites, 2.5 x 2.5 x 2.3 cm, crystals up to 8 mm, Francon Quarry, Montreal, Quebec, Canada. © Rob Lavinsky, www.iRocks.com. Used with permission.
Discovered in 1966 in the Francon quarry in Montreal, Quebec, weloganite is a very rare strontium zirconium carbonate mineral. To date, the only known gem-quality material has come from this now closed site.
Although this transparent to translucent gemstone can show attractive, pale yellow colors, it has perfect cleavage and a hardness of just 3.5. Any stones worn as jewelry would be very susceptible to cracks and scratches. Protective settings and occasional wear would be advisable.
You’re more likely to find any rare, faceted weloganites in mineral collections or museums than jewelry collections.
Weloganites are pyroelectric. When heated, they generate an electrical charge.
Some weloganites may also have triboluminescence. When rubbed or broken, they may show blue light.
There are no known synthetic weloganites or enhancements for these gems.
Aside from the type locality, weloganites occur in the Lafarge Montreal East quarry, also in Montreal, the Poudrette quarry in Mont Saint-Hilaire, Quebec, the Demix-Varennes quarry in Varennes and St-Amable, Quebec, and the Eden Lake Complex in Manitoba.
Outside of Canada, the only known source of weloganites is the Pilanesberg Alkaline Ring Complex in North West province, South Africa.
Gem cutters have faceted clean, yellowish stones, usually under ½ carat.
National Museums of Canada (Ottawa, Ontario): 4.27 (light greyish yellow); 0.52 (light yellow).
Store weloganites separately from other harder stones to avoid contact scratches. Clean weloganites with a soft brush, mild detergent, and warm water. See our gemstone jewelry care guide for more recommendations.
Weloganites, about 8-9 mm on edge at the top of the largest crystal, Francon Quarry, Montreal, Quebec, Canada. Photo by Modris Baum. Public domain.
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