Why don't you get your own and have it set. You can find tanzanite all over the place and in many calibrated sizes. I personally wouldn't trust LOGR when it comes to treatments, synthetics, etc. . .
Because that would have been the smarter thing to do but I had already ordered it! And you know what happens when you're sitting around waiting for the mail . . . you obsess. Or at least I do.
But, I got my ring and I don't know if it's coated or maybe even secretly fosterite but I do know that I am SMITTEN! I can't stop looking at it and moving it around in the light to see the different shades of purple and blue.