I bought a sapphire off an EBay auction in the hopes that it would be a dark, yet visibly translucent blue (this is why you never trust studio lighting). I got one of those things, and very close to the other.
That said, I'm pretty sure this was heat treated to begin with. Does anyone know of a procedure to de-heat-treat it (or in other words, lighten the color just enough to be visibly blue and translucent again)? I have access to a 1100 oC electric furnace and more than a few chemicals depending on what's needed.
(Alternatively, if someone could direct me to a place that sells similar size/quality but slightly less dark sapphire roughs, I'd appreciate it.)
One thing to check out: that surface looks super glossy. Check for any glass attached to the surface, as many glass-filled sapphires will get that appearance. The only particular, sometimes-reliable method of breaking down that iron-titanium intervalence charge transfer I know of is beryllium diffusion, but you should absolutely never handle powdered beryllium at home (or anywhere) so this is not an option for the home-heater.
I can build higher-temperature furnaces (up to 2000 oC) relatively easily, but I'll have to work something out for decent temperature control (I've heard Pt-Re thermocouples work well for this?) I was going to build a big one to make my own synthetic sapphire from melt, so this might be a nice exercise towards that if I need something in that range.
I took a closer look at the stone and found it has several small (~0.5mm) raised bumps on every surface - are these glass? Not entirely sure what I'm looking for, very new to the world of faked gemstones. It was fairly cheap for its apparent quality, so that is pretty suspect. Are there any chemical tests I can do?
I've worked with beryllium before (did home chemistry when I was younger to isolate periodic elements), so I'm no stranger to its hazards, but I'd prefer not to work with it if I don't have to. Plus, I only have the one stone, so I'm loathe to try it without knowing it'll work.
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