Simply put, this is an exceptional crystal of grnadidierite, and a killer thumbnail of the species. It is **actually terminated** and not just a thin crystal but rather has some blockiness. The faces of the top are a bit etched, though when a bit of light reflects off the top, you can clearly see the completeness of the crystal. Even the translucency of this crystal is better than most-- this is the material that gets used for cabbing, those are almost exclusively broken shards of gem rough. This is not cheap, nor is it perfect (there is a chip on the top edge) but you would have a very hard time finding a larger, more complete or translucent example of the species... this thing was expensive even in Madagascar.
In 2016 there was a rather spectacular find of this very rare blue-green borosilicate mineral in southern Madagascar. I has seen some available on my previous trip, but the quality was horrible-- they were basically formless shards, and few if any had crystal faces much less a termination.
There was a little bit more available this time around, but once again, the majority were shards. Still, I looked through them and was able to obtain a small number of pieces that had visible crystal faces, and even a few with terminations. This one has both.
It really is *very* good for what it is.....