These are lab created 'Space Laser' garnet, or more technically speaking chromium + neodymium YAG (Yttrium Aluminum Garnet) facet rough. Each is labelled with its gram weight and letter in the photo and they can be purchased individually.
This is a hot new material, dual-doped neodymium+chromium YAG. This material allows the creation of self-switched pulsed lasers which are hard to grow but save weight and have fewer points of failure, making them great for use in very demanding applications. In particular these are meant for use in space! They are grown by a top US photonics company and a laser built around one of these will be on the 2028 Mars rover(!!!) in addition to their routine use on satellites. In theory a laser crystal cut from one of these very same crystals could be on mars in a few years! The material we got is from the very tops of the crystals which tends to concentrate any chemical or structural imperfections and as such can't be used, but the main bodies of these crystals have no doubt made it into functioning lasers.
From a gem perspective it is also amazing material. It looks similar to our classic christmas garnet, with a rich green base and strong red fluorescence, but with an even richer and slightly bluer green base. It also has odd pale yellow fluorescence under short wave unlike classic christmas garnet which is red in short and long wave, so it is easy to distinguish from the more common chromium YAG. We have a limited amount of this material and it's one of the best things we've ever gotten.
This is an ideal material for faceting. It cuts and polishes like butter and has excellent optical properties in addition to its amazing color.
