Purple Nd:GGG Lab Garnets, Magnetic Gem Rough

These are rough purple Nd:GGG, Gadolinium Gallium Garnet, used in high end laser systems.  

This material has a beautiful color that changes under different lighting, varying based on color temperature of LEDs or differently under OLEDs or CFLs.  Due to the strong paramagnetism of gadolinium, they can be picked up with a rare earth magnet.

GGG is an exotic lab-created garnet and an old classic of industry and the gem world. It it was once grown for gem usage, but once CZ hit the scene and got insanely cheap the demand for other gem crystals plummeted.  Today it is primarily grown as a growth substrate, a material whose crystal lattice makes it useful for growing other, harder-to-grow crystals on top of it.  This is old material grown in England, likely for for use in lasers.

In the gem world it is prized for its optical properties, with a dispersion in particular that is very close to that of diamond. Faceted GGGs look very much like a diamond in terms of fire.

GGG has a hardness just over 7, is easy to cut and good for use in jewelry though I wouldn't recommend it for a ring.