These are cores and wafers of colorless optical sapphire grown by Rubicon, one of the top US growers of sapphire, and purchased from a factory closing auction. These are a mixture of rejected material (likely for surface chips or maybe minor optical misalignments) and cores/wafers that just didn't get used before the factory closed. These were grown for use in high end optics and as a substrate to grow bespoke computer chips on. These can of course be faceted as gems and are just extremely cool! A few have chips and/or cracks and range in size from small pucks to large rods and cores.