Diamonds are often graded by the retailer from experience and via merchant agreements. We insist that our merchants supply at least the minimum standard that we state and then we check every stone ourselves. We warrant the grading in writing on our valuations, each of which is personally signed by a director of this company.
Some diamonds are independently graded by a gemological laboratory. There are only a handful of truly independent and accredited laboratories around the world, the main ones being AnchorCert, EGL, HRD, IGI and GIA. Certification costs both time and money so it's uneconomic to have such certification on every piece. We reduce the cost by sending multiple stones for certification in large batches to keep our certified items at the low prices that you expect from Ampalian.