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August 1 eNews Mini-Quiz Question


You are examining a transparent, faceted blue gem. You measured the RI as 1.633 to 1.638 and found the optic sign is uniaxial. What should you do next?
a) check specific gravity
b) check UV
c) check pleochroism.


The RI is between Tourmaline and Peridote so I would do (a) SG.


next step is a.: specific gravity


Check for pleochroism because the possibilities are Topaz (blue) or Paraiba Tourmaline or Indicolite.


Option a) check specific gravity


A)check specific gravity is next step.


personally would have used a polariscope first then maybe the refractometer.
I then would have used a spectroscope to see if I could get a spectrum. even may have used this after the polariscope
I would think that with the RI and the Birefringence that you have said, if it were uniaxial negative that the gem would be apatite and I should get a good didymium spectrum.
No need to check specific gravity if that were the case as the spectrum would be diagnostic
please make comment if you wish thanks