Kelly Mine Smithsonite Wire Wrap

[Mark]

Almost forgot, Hemimorphite, it has incredible blues too, and has gotten much more popular the last few years.

Mark

[rocks2dust]

I agree that Peruvian opal can also look like that. I'll add that chrysoprase (RI 1.53-1.54, SG 2.58-2.64) can sometimes be that aqua blue color. Smithsonite (RI 1.621-1.849, SG 4-4.65) and hemimorphite (RI 1.614-1.636, SG 3.3-3.5) are both very soft and scratch very easily, but you likely don't want to do a scratch test on a finished stone. If the back is flat and polished and you know anyone with a refractometer, that would narrow things down, as would a specific gravity test.