If Opal has a GRC jewelry appraisal certificate, it can basically be judged to be true. Because the identification of opal is relatively perfect, it is GRC. Because opal is one of the most difficult jewels on the market to get a jewelry appraisal certificate. Many appraisal institutions can't reach this appraisal level. GRC passed the full-spectrum color opal trade name recognition on 202 1. It is the first choice for identifying opal.