Chrome dioptase ?

[wilsonintexas]

I have some green material, perfect cleave, double refractive.

Bit the ri is 1.65and the listed ri i find is 1.66


Is there a range of acceptable ri for this?

I can mail a piece to someone to help id it. they cn keep the piece.

[Barbra Voltaire, FGG]

Dioptase is colored green with copper, not chromium.

[Stephen Challener]

Probably a bit low for diopside (which I assume you mean, I mix them up too sometimes).
Where dis you come across it? Diopside will have perfect cleavage in two directions at 90 degrees, which would eliminate a lot of other possibilities.

[wilsonintexas]

I bought a large lot at an estate sale. I have about a kilo. I would be glad to send a sample for you to test and keep.