GDCS
What is GDCS?
A price list for lab-grown diamonds and a sustainability record for 500 jewellery brands, built on the AIDI Trust Index. It is published by AIDI, the Association for Intelligent Diamond International, a not-for-profit incorporated in Canada. About →
Is a GDCS value an appraisal, a grade or an offer?
None of these. It is a calculation from public figures. It is not an appraisal of any one stone, not a grade, not an offer and not advice. This site grades no stone and issues no certificate.
Does any brand pay to be here, or to change its result?
No. We read public documents. No brand asked to be included and none paid, and no brand can pay to change a result.
Prices
Where do the prices come from?
From the GDCS formula. Price per carat is a price level, times carat to a power, times colour and clarity coefficients; cut, shape and growth method then multiply the stone's value. The level is refitted each month over the lab-grown rows of one public data set, the Diamond Price Index (CC BY 4.0); today the 1 ct reference is US$ 715 per carat and the power is 0.158. Every coefficient is set by GDCS. Price list →
Are these the prices shops charge?
No. None is a seller's price. The list is a benchmark in US$ per carat for loose stones on a round basis, so that any price can be compared against it.
Why is a brand's price above the benchmark?
Its AIDI tier adds a premium: Diamond 9.7%, Gold 7.3%, Silver 4.9%, Bronze 2.4%, Under review 0%. A brand carries the premium only once at least one of its product facts has been confirmed by someone independent; otherwise it carries the benchmark. 9.7% is what consumers told PwC in 2024 they would pay extra for goods made sustainably.
How are fancy colours priced?
From the white benchmark of the same carat and clarity at colour F, times the hue and the intensity, with cut taken as Excellent.
How often does it change, and can I see earlier versions?
The price level is refitted every month; the coefficients are reviewed once a year. Every change carries its date, and earlier rules stay published beside the current ones. Method →
Brands and tiers
What does a brand's tier say?
It is the brand's grade in the AIDI Trust Index, which reads what each brand publishes about sustainability across seven areas and records which statements someone independent has checked. It says what a brand has published and who has checked it, not how the brand behaves. AIDI Trust Index →
A brand's record is wrong. How is it corrected?
Send the public document to [email protected]. If it changes the record, the change appears in the next monthly issue, with its date.
Grey List
What is the Grey List?
Jewellery and lab-grown diamond companies for which a fixed check of four public places (the company's website where it has one, stock-exchange filings, three public registers and a fixed set of searches) found no statement, published by the company, on the environment, its workers, where its materials come from, or how it governs any of that. It says this and no more. Grey List →
Does a name on the list mean the company has done something wrong?
No. The list does not say that a company breaks any law or standard, or that its products or prices are worse. It records what the company has published, which here is nothing.
How does a company leave the list?
By publishing something on any of these subjects: a report, a policy, a paragraph on its website. The list is checked again every month and a company that has published is taken off without having to ask; it can also send the page to [email protected]. Leaving costs nothing, and nothing paid takes a name off or keeps one off.
Why are so many companies on the list in India, and many without a website?
Issue 2026-11 checked 533 companies, 466 of them in India, taken from Indian trade lists. Since rules grey-v2 every candidate is checked, with or without a website; a company without one is checked in the remaining places and marked “no website”.
Why is no company in mainland China on the list?
In issue 2026-11, 67 companies in mainland China were checked and 64 could not be completed. For a company with no website, a search of WeChat official-account articles stands in for the website. The search services a program may use cannot see those articles, and the one that can, Sogou WeChat search, refuses programs, so that check is done by a person. Until it is, those companies are not completed, and any doubt keeps a company off.
Who decides, and how can a decision be checked?
The rules are sealed before the list of companies to check is drawn up, and that list is sealed before any company is checked. Two readers walk every place independently and a named reviewer signs. Every page read is archived with its hash, and the sealed rules and each issue are published as data.
Standards
What are the GDCS standards?
Three published texts: laboratory-grown diamond, whose grades the valuation console uses; synthetic ruby, sapphire and emerald (testing and grading); and enamel (identification and classification, citing DZ/T 0413—2022 without reproducing it). The synthetic-gemstone and enamel standards are trial editions in Chinese and English; the Chinese text governs. Standard →