Identifying gemstones with just RI and SG

Does any have a list of the gemstones which can be definitively identified with just an RI and SG test?


Hi Richard, most gemstones can be identified just doing an RI and SG even though when learning gemmology you are taught to do at least 3 to 4 tests. as long as you can test the RI for single of double refractive index and the birefringence then the SG you should be able to identify most. although using a refractometer is not as easy as is seems to ensure the gem is signal or double refractive and ensuring you get the exact Birefringence

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Hi Richard, also forgot to mention that the RI also should look at if the gem is Uniaxial or Biaxial and optically positive or negative.
This is a necessity if the RIs of 2 gems are very close such as Quartz and Scapolite which have close RI and Birefringence the only way to distinguish by RI is that Quartz is Uniaxial positive and Scapolite is uniaxial negative hope I am not getting too technical thanks

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