Description Standards

Product Descriptions (draft 10/12/25)

Gemmological descriptions included in the Product Description pages of this website are generally in line with the procedures of the Gemmological Institute of America (GIA) as set out in the following documents:
•    Colored Stone Grading Lab Manual (12/2018)
•    

Weights
Gemstone weights are reported to the nearest 0.01 cts using balances that are regularly checked against UKAS (United Kingdom Accreditation Service) certified calibration weights.

Dimensions
Dimensions are measured using either a JQA-marked Japanese Mitutoyo vernier caliper conforming to JIS (Japanese Industrial Standards); or a Swiss-made Sylvac digital vernier caliper, with traceability to the Swiss Federal Institute of Metrology.
Measured dimensions are reported to the nearest 0.01mm.
In the case of rounds, the reported diameter is the average of two measurements taken approximately 90 degrees apart. These are not necessarily the minimum or maximum diameters.