These are loose calibrated faceted stones of LYSO (Lutetium Yttrium Oxyorthosilicate). All show bright blue fluorescence strong enough to give them a full color change to light blue in direct sunlight. Some also have a mild afterglow, showing a blue glow after exposure to UV which can be seen in cupped hands.
LYSO is a very unusual crystal grown for use in science and industry. It has a clear base and very strong blue fluorescence. It glows incredibly bright under UV light as well as higher energy radiation, and because of this it can be used to detect invisible gamma rays, xrays and even alpha rays. This type of LYSO has been optimized for ultra strong fluorescence with no afterglow (it does not glow in the dark, only with UV exposure). Its fluorescence is so strong it has a striking blue glow in sunlight--this effectively gives it a color change effect, since it looks colorless under room lighting and light purple-blue outdoors. It has a very interesting and unique look which you can't find anywhere else.
Asianometry on youtube recently made a cool video about this material which you can watch here https://www.youtube.com/watch?v=XpYYGiUX0x0
LYSO is not very hard at around 5.8, just under tanzanite, and as such is not a good choice for a ring, though it would be great in a pendant or earrings.
