Weloganite is a rare carbonate mineral. Regarding gem quality crystals, it is a one locality mineral that was found at the famous Francon Quarry near the city of Montreal, Quebec, Canada. The quarry has now been reclaimed as a landfill and is not producing any new specimens, making existing specimens true rarities. The mineral is named for famous geologist, W. E. Logan, the founder of Canada’s Geological Survey.

Weloganite forms as crystals that grow into tapered pseudohexagonal prisms that are often completely tapered to a point. Gems are fairly small and typically moderately included and their color can be a very attractive lemon or honey yellow.

Chemical Formula: Sr3Na2Zr(CO3)6•3(H2O)
  Hydrated Strontium Sodium Zirconium Carbonate
Molecular Weight: 814.16 gm
 Composition: Sodium 5.65 % Na 7.61 % Na2O
  Strontium 32.29 % Sr 38.18 % SrO
  Zirconium 11.20 % Zr 15.13 % ZrO2
  Hydrogen 0.74 % H 6.64 % H2O
  Carbon 8.85 % C 32.43 % CO2
  Oxygen 41.27 % O    
    100.00 %   100.00 % = TOTAL OXIDE


Crystallography: Triclinic – Pinacoidal
Crystal Habit: Crystals, roughly hexagonal, tapering, the prism faces deeply grooved and striated, withrough pyramidal terminations and a flat pedion, to 10 cm; may be massive.
Twinning: About [103] repeated at 120º.


Cleavage: Perfect on pseudo-{0001}
Fracture: Conchoidal
Tenacity: Brittle
Moh’s Hardness: 3.5
Density: 3.20 – 3.22 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive
Other: Pyroelectric. May be Triboluminescent with blue light (http://www.mindat.org/mesg-6-204391.html)


Color: Lemon-Yellow, pale Yellow, Amber, commonly zoned in basal sections; Colorless in thin fragments.
Transparency: Transparent to Translucent
Luster: Vitreous
Refractive Index: 1.558 – 1.646  Biaxial  ( – )
Birefringence: 0.0820 – 0.0900
Dispersion: Weak
Pleochroism: None