This is one of those stones that is just really hard to photograph, so please forgive the variations in images, the stone changes a lot with perspective and light.
This is a natural ??? (here’s where I need help). I know it is natural for a few reasons (source, provenance, etc), so I can say with certainty it’s not synthetic, but I’m not sure what it is. It has no flat surfaces, all edges are rounded such that I can’t get an RI reading, but it’s SG is easily measured and it’s about 4 (total weight 10ct, displaces 2.5ct). It’s super hard, even without a sharp edge it easily scratches glass, and although I don’t want to take a ruby to it, I am quite sure it’s hardness is over Mohs 7-7.5, it may be closer to 8 or higher, just given how easily it left a sliver of a deep cut in glass. The stone looks black (to my eyes) in most light, it takes a lot of light or changes in photo settings to bring out its actual color, which is a sort of forest green (see pic with light). If ala exhibits am interesting chatoyance, the effect is confined to one side, and is quite pronounced when the light hits it the right way, it has the sort of silver silky colored chatoyance like some rubies. I don’t know where it was first mined/found, but to save you all me rambling about its unique history, suffice it to say it’s been around the block, so to speak, it’s centuries old (ie, it’s been that long since it was last worked), yet it’s hard enough to have survived that long with virtually no surface blemishes (none really visible).
I’m guessing it’s a type of sapphire,
but I’m anxious to get opinions. Any suggestions would be much appreciated!