These are very unusual gray to purple-grey Nd+ laser garnets (Nd:YAG). While the original crystals were supposed to be grown with light-toned violet color, these turned out having a purple-gray, pure gray, or even bluish-gray hue. They look very similar to natural gray spinel!
Because these crystals weren't designed to have these color, there's some variation in tone (as with natural rough). As-grown, the crystals tend to be a pure blueish-grey color at the tip fading into a purple grey at the base, giving a range of colors. Because of that, no two stones are exactly the same, and there will be some differences in color between gems.
Cut stones are bright and very beautiful with a unique look. In addition, the purplish component (from the Nd-doping) will vanish under CFL bulbs, which can make the color of the stones shift to be a purer gray.
With a hardness of 8.5 it is ideal for use in all kinds of jewelry.
