Three Cut Stones Under CL

CL colours of three colorless cut stones: the blue CL colour is the intrinsic feature of a 13.18 ct brilliant-cut topaz of 16 mm diameter. A brown CL exhibits the 4.12 ct scapolite in the lower left, and the red CL is due to minute amounts of threevalent chromium ions in an old synthetic leucosapphire. Cond.excit.: 7.5 kV; 0.8 mA. Dr. Johann Ponahlo, Vienna.

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