Step 3: Practical Gemology
Testing for optic figure and sign is an important technique for gemstone identification. You’ll need a polariscope and a condensing sphere. If your polariscope doesn’t have built-in magnification, you’ll also need a hand held or head mounted magnifier.
Finding Interference Colors
Begin by setting the polariscope filters to their darkest position. Rotate the gem between the filters and look for interference colors. These are colors that aren’t normal for the …
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