Ekanite
Structure : TetragonalHardness : 6.25
Specific Gravity : 3.3
Refractive index : 1.57
Most Ekanite comes from Sri Lanka, but deposits have also been found in Canada and Russia. Gem quality Ekanite is relatively uncommon. As a rule, Ekanite gemstones are green but there are also yellow and red varieties.
Chemically, it is ThCa2Si8O20 (by weight, approximately 30% thorium). On the Moh's hardness scale it ranks 6 to 6.5.
The rather noticeable radioactivity of the stone is due to its thorium content. Over time, the Ekanite will deteriorate as a result of the damage caused to the crystalline lattice by the alpha emissions.
Activity: ca. 3,000 pCi (100 Bq) of Th-232 with all the members of the decay series in secular equilibrium.