This is lab created lithium niobate facet rough. Pieces can be purchased by their weight range as shown in the photos.
This is lithium niobate, a crystal which plays a larger role in your life than you might think. In addition to more exotic uses like frequency doubling in lasers and use in fiber networks lithium niobate is an essential component of cell phones, where its piezoelectricity allows it to act as a resonator for filtering radio signals. It is also pyroelectric, triboelectric and photoelastic among other properties that make it indispensible for all kinds of scientific and industrial applications.
Lithium niobate was also briefly used as a gemstone back in the 60s, though it is vanishingly rare today. It was mostly used as a diamond simulant but it really doesn't work well for that simply because it's much brighter and more dispersive than a diamond. That means cut stones give of brilliant rainbows of color, and it makes for an amazing gem in its own right for those reasons. Note its hardness is 5.5 so it is not a good stone for rings but makes incredible pendants
