A grading report is issued by a laboratory with no stake in the sale. It describes the stone; it does not value it. Two stones with identical reports can be worth noticeably different amounts.
Which laboratories
For diamonds, GIA and IGI are the most widely recognised. For coloured stones, GRS, SSEF and Gübelin carry the most weight, particularly on questions of origin and treatment. Grading is a judgement, and standards do vary between laboratories, which is why the issuing lab matters.
What to check
- The report number. verify it on the laboratory's own site. Every stone we list links straight to that check.
- Natural or laboratory-grown. stated plainly, near the top.
- Treatment. for coloured stones this is often the single largest factor in price.
- The plot. where the inclusions sit, not just the grade.
- Measurements. these tell you how large the stone will actually look.
What a certificate does not tell you
It will not tell you whether the stone is beautiful, whether it is fairly priced, or whether it suits the person wearing it. That still requires seeing it.
