Introduction
Every diamond above 0.30 ct at Arete Diamond arrives with a grading report from an independent laboratory — and the choice of laboratory is not arbitrary. Which lab graded the stone determines how much you can trust the grades printed on the report, how confidently you can compare one diamond against another, and whether the price you are paying aligns with what you are actually getting. (Melee diamonds — the small accent stones set into jewellery — are graded by Arete Diamond's own gemologists and accompanied by an Arete quality guarantee rather than an external lab report.)
This article explains which grading laboratories Arete Diamond accepts, why we chose them, and what quality thresholds we apply regardless of the name on the report. If you are new to the differences between grading laboratories, start with Laboratory Profiles for an overview of the major labs, and Why Grading Differs Between Labs for a detailed explanation of how and why grades vary from one laboratory to another.
For our broader quality commitments — sourcing, disclosure, and certification requirements — see Arete Diamond Standards.
Key Points
Natural Diamonds Above 0.30 ct: GIA, HRD Antwerp, or IGI
Every natural diamond above 0.30 ct sold by Arete Diamond carries a grading report from one of three laboratories: GIA (Gemological Institute of America), HRD Antwerp (Hoge Raad voor Diamant), or IGI (International Gemological Institute).
Among these, GIA is our primary recommendation — and the reasoning is straightforward: GIA grades are the benchmark the global diamond market prices against.
GIA developed the 4Cs framework and the International Diamond Grading System that every other laboratory now uses. Its grading process involves multiple independent gemologists assessing each stone without knowledge of who submitted it or what grade is expected. When a diamond falls on the boundary between two grades, GIA's protocols resolve toward the more conservative call. The result is that a GIA G colour is reliably a G. A GIA VS2 is reliably a VS2. See GIA Profile for the full methodology.
Why does this conservatism matter for you as a buyer? Because diamond pricing is grade-dependent. The Rapaport Price List — the wholesale pricing reference used across the trade — assumes GIA grading. When you see a diamond priced as G colour, VS2 clarity, the market expectation is that those are GIA-calibrated grades. A stone carrying the same stated grades from a more generous laboratory may actually sit one grade lower by GIA standards, and the price difference between adjacent grades is significant — often 10–20% per grade step on colour, and comparable on clarity.
By accepting only GIA, HRD Antwerp, or IGI reports on natural diamonds above 0.30 ct, we ensure that the grades you see on our product pages come from laboratories with documented, reproducible methodologies. GIA-graded stones offer the closest match between stated grade and market pricing; HRD Antwerp provides similarly rigorous grading with particular strength in European-sourced stones; IGI is widely recognised, though its natural-diamond grades are sometimes perceived as slightly more generous than GIA's.
Each product page identifies which laboratory graded the stone, so you always know the basis for comparison. See Why Grading Differs Between Labs for the specific calibration patterns across laboratories.
Lab-Grown Diamonds: IGI
For laboratory-grown diamonds, Arete Diamond accepts reports from the International Gemological Institute (IGI).
IGI is the dominant grading authority for lab-grown diamonds worldwide. When the lab-grown market began scaling commercially, IGI invested early in grading capacity for these stones. Today, the overwhelming majority of lab-grown diamonds reaching consumers — whether purchased in Prague, New York, or Mumbai — carry IGI reports. See IGI Profile for the laboratory's history and methodology.
This market position matters. Because IGI grades such a large proportion of lab-grown diamonds globally, its grading becomes the practical standard for that category. When you compare lab-grown diamonds across retailers, most will carry IGI reports, giving you a consistent basis for comparison within the lab-grown segment.
IGI applies the same 4Cs framework to lab-grown diamonds as to natural stones: colour, clarity, cut grade, and carat weight. The report clearly identifies the diamond as laboratory-grown, and each report number can be verified through IGI's online database. See Online Report Verification for how to check any report.
One important distinction: IGI's grading calibration on natural diamonds has historically been perceived as slightly more generous than GIA's, particularly on colour and clarity. This calibration difference is one reason we require GIA — not IGI — for natural diamonds. For lab-grown stones, where IGI is the market standard and price comparisons are made within the IGI-graded population, this calibration question is less consequential. You are comparing IGI-graded lab-grown diamonds against other IGI-graded lab-grown diamonds, and the pricing reflects that grading standard.
Quality Thresholds: What Every Report Must Include
Regardless of whether a diamond is natural (GIA, HRD Antwerp, or IGI) or lab-grown (IGI), the grading report must meet a minimum documentation standard before we list the stone. A report that omits key data is not a report — it is incomplete information.
Every report accompanying an Arete Diamond purchase includes:
- Full 4Cs grading — carat weight measured to the hundredth, colour grade on the D-to-Z scale (or fancy colour system where applicable), clarity grade from Flawless to Included, and cut grade for round brilliants
- Proportions data — table percentage, crown angle, pavilion angle, girdle thickness, total depth, and star/lower-half facet lengths where reported
- Clarity plot — a diagram mapping the location, type, and relative size of inclusions and blemishes. This is your visual guide to what is inside the stone. See Clarity Characteristics for how to read inclusion types.
- Fluorescence assessment — graded from None to Very Strong, indicating the diamond's response to ultraviolet light. See Fluorescence for why this matters.
- Laser inscription — the report number inscribed on the diamond's girdle, creating a physical link between the stone and its documentation
- Online verifiability — every report number must be checkable through the issuing laboratory's verification tool
If any of these elements is missing, we do not list the diamond. These are not premium features — they are the minimum information a buyer needs to make an informed decision.
When We Recommend One Lab Over Another
If you are buying a natural diamond above 0.30 ct from Arete Diamond, it will carry a report from GIA, HRD Antwerp, or IGI — each product page identifies which laboratory graded the stone. If you are buying a lab-grown diamond, it will carry an IGI report. Melee diamonds carry Arete Diamond's own quality guarantee.
When comparing natural diamonds across retailers, remember that a G/VS2 from one laboratory is not automatically equivalent to a G/VS2 from another. The Lab Comparison cluster covers calibration differences in detail.
For lab-grown diamonds graded by laboratories other than IGI, the same principle applies, though the practical impact is smaller: the lab-grown market is more price-competitive and less grade-sensitive than the natural market, and IGI's dominance means most comparisons will be IGI-to-IGI regardless.
Summary
Arete Diamond's laboratory preferences reflect a single principle: the grades on the report should mean what the market understands them to mean.
For natural diamonds above 0.30 ct, that means GIA, HRD Antwerp, or IGI — laboratories with rigorous, documented methodologies. GIA remains our primary recommendation as the laboratory whose grades anchor global pricing. HRD Antwerp offers comparable rigour with particular strength in European-sourced stones. For lab-grown diamonds, IGI is the standard — the laboratory that grades the vast majority of lab-grown stones worldwide. Melee diamonds are graded by Arete Diamond's own gemologists and accompanied by an Arete quality guarantee.
Beyond the choice of laboratory, we apply a consistent documentation threshold: full 4Cs, proportions, clarity plot, fluorescence, laser inscription, and online verifiability. These requirements exist so that every diamond on our site gives you the information you need to evaluate it independently — not on trust, but on data.
For the broader context of Arete Diamond's quality commitments, see Arete Diamond Standards. For help interpreting any grading report, see How to Read a Report.