This is a truncated D20 lab ruby weighing in at 36ct set as a pendant in 14k yellow gold wire. I cut this one myself and I call it 'D21' because it ended up with an extra face by accident. I faceted this stone on our CutKit™1 faceting setup.
Note that the 2 came out a bit wrong during the sandblasting but it is still readable.
This ruby was grown by the Czochralski method, an advanced growth technique that produces more perfect crystals with purer chemistry than the typical stones used in jewelry. This one is likely codoped with a little bit of iron to give it a more pure red-red color vs the slightly magenta-red of a pure chromium ruby. I don't know for sure what this was grown for but it was likely a technical application like high end watch cases.
