Each piece of jewellery is thoroughly scrutinized for diamond quality, as well as overall manufacturing and craftsmanship. Costco’s team of Gemologists, all of whom have graduated from a Gemological Institute of America (GIA) program, inspect for diamond color, clarity, cut, and carat weight. When purchasing diamond jewellery from Costco, you can be assured you will receive quality jewellery at an unparalleled value.

We guarantee that all diamonds supplied by Costco Wholesale have a clarity to be "VS2" or better and color to be "I" or better as outlined by the industry standard in the Gemological Institute of America (GIA) grading guide. Costco only sells diamond cut grades that range from Very Good to Excellent.

Although treating diamonds is an accepted practice among many jewellers, Costco sells only untreated diamonds

All diamond jewellery items from Costco come with some type of certification or documentation. Depending on the characteristics of the item, it may come with one or more of the following reports:

Costco Article of Description

When you purchase an article of jewellery with a diamond of less than 1.00ct, you will receive an Article of Description written by one of our Gemologists, with a degree from GIA, detailing your jewellery piece.

GIA Diamond Grading Report

When you purchase an article of jewellery with a 1.2ct center diamond or larger, you will receive a Diamond Grading Report from the Gemological Institute of America (GIA) detailing and mapping the diamond. Also provided on center stones with higher colour and clarity than standard I colour/VS2 clarity.

Jewellery Grading Report

When you purchase an article of jewellery with a 1.00ct center diamond or larger, it will also include a Jewellery Grading Report describing the Jewellery piece. This report will not have a monetary value listed, however, you can contact the company that issued the report and request an insurance appraisal.