These are faceted Czochralski pulled cobalt spinel grown for use in lasers. Each is labelled with its weight and letter in the photo and they can be purchased individually.
This is cobalt spinel, and it's the bluest gem there is! Maybe the bluest thing there is--just pure, vivid electric blue--the camera is confused by it and adds magenta flashes because it's so overwhelmed. While it is sometimes found in nature as a very rare and prized gemstone, cobalt spinel is also valuable in industry. It can act as a q switch in lasers, transforming a continuous firing laser into a powerful pulsed laser which releases its energy in discrete bursts. It has the most vivid blue color you are likely to ever see in a gem--normally materials in this color range are soft like hauyne or water soluble like copper sulfate, but cobalt spinel has a hardness of 8 and is ideal for use in all times of jewelry. We only managed to get a limited amount but we're going to do everything we can to secure a steady supply.
Note that a few of the stones were from a piece with lower concentration of cobalt, so their color is still pure but less vivid. These are still very beautiful but priced lower to reflect that.
Synthetic spinel is a pretty familiar material, but the typical, common stuff is grown by the flame fusion method. While this method is cheap and fast it has some limitations--it can only produce relatively small pieces and the material produced is not precisely the same as natural spinel, with an excess of alumina. As such is not suitable for high end optical applications, where the more advanced and expensive Czochralski pulling method has to be used. Czochralski pulling also produces crystals of higher purity with a more vivid and electric color--the best flame fusion spinel is quite good but doesn't stand up to the best czochralski-pulled.
