How to find out the diamond appraisal value?

To classify appraisal value of a diamond you need to have information about the origin of the diamond (natural or synthetic), enhanced or untreated diamond, its main estimated (4Cs - carat, color, clarity, cut) and additional (luminescence) characteristics.
Having all the necessary data one should refer to the evaluation sheet of one of the main indicators of the market for cut diamonds (Rapaport, IDEX, The Guide, etc.) and to define the appraisal value of the diamond on the main evaluation sheet then take into account the discount for luminescence, type of gemological conclusion or stone certificate, and trade discounts for your market segment (based on the type of transaction of purchase and sale).
The resulting figure will define the value of your diamond with an accuracy of ± 20% for the region covered by the market indicator.
You can also study the offers and discounts of sales agents (dealers and retailers) in the diamond market in your region yourself but this method although it gives higher accuracy in value estimation of your stone requires much more effort and time. But to proper estimation of the market value without errors you need to contact the relevant qualified specialists.