I had study about lab created Tanzanite and realize that all that I tested never goes over RI 1.64 and the Genuine Tanzanite RI reads 1.68 to 1.72. I use these stones by viewing the double light that shows blue/purple and that of a lab created Tanzanite doesn't show but a single color. I've used every test possible to me and found that there's no imitation or lab created Tanzanite on the market that can fool the Refractomer Scale (RI) because it always read lower on the scale at 1.64 the highest reading on fake Tanzanite toward that of a Genuine Tanzanite that is a lot higher then 1.64 so when someone brings in a Tanzanite that reads 1.68 to 1.72 I'm sure we have a genuine Tanzanite. I took all my raw material Tanzanite and test them with the RI before cutting them and most reads 1.688 to 1.719 so as long as the making of the lab created or imitation on Tanzanite doesn't change we may stay ahead of the game.