Carletonite: Gemstone Information

Pale blue transparent carletonite has been found at Mt Saint Hilaire,Quebec, Canada. The composition is KNa4Ca4Si8O18(CO3)4 (OH,F)H2O and it crystallizes in the tetragonal system. The hardness is 4.5 on Mohs’scale with perfect cleavage. The SG is 2.44 and the RIs are 1.517 and 1.521 with a birefringence of 0.004. Carletonite is found in nepheline syenite.Some Mt Saint Hilaire material has been found in opaque to translucent pink, white and grey with colour zoning common. Some of the blue specimens may show blue to pinkish brown pleochroism.