A diamond certificate is a gemological record. It documents what a stone is, what it weighs, and how it has been graded on the criteria that determine its quality. It is not a warranty, not a valuation, and not a marketing document. Understanding what a certificate contains — and what it does not — is the most useful thing a buyer can do before purchasing a diamond or a cultivated gemstone.
The International Gemological Institute (IGI) is the most widely used certification body for lab-grown diamonds globally. Every diamond and cultivated gemstone in the DHARIN collection is IGI certified. This is what the certificate contains and what each field means.
What IGI is
IGI was founded in Antwerp in 1975. It operates grading laboratories in Antwerp, New York, Mumbai, Hong Kong, Dubai, Tokyo, Bangkok, and other centres. It grades both natural and lab-grown diamonds, as well as coloured gemstones including sapphire, emerald, and ruby.
For lab-grown diamonds specifically, IGI has graded more stones than any other major gemological laboratory. This is partly a function of timing: IGI moved early to establish a rigorous grading framework for lab-grown material when the category was expanding, and the industry converged on IGI as the standard. As of 2025, IGI certification is the most commonly referenced credential in fine jewellery retail for lab-grown diamonds worldwide.
The certificate accompanies the stone. The stone is laser-inscribed with its IGI report number — a sequence of digits visible under 40x to 50x magnification on the girdle of the stone. The inscription allows the physical stone to be matched to the certificate at any point.
The 4Cs: what they measure
The 4Cs framework — cut, colour, clarity, and carat weight — was standardised by GIA in the 1950s and is now the universal language of diamond grading. IGI uses the same framework. Each C measures a different dimension of quality, and together they determine both the appearance and the price of a stone.
Cut
Cut is the most technically complex of the four, and the one that most directly affects how a diamond looks to the eye. It does not refer to the shape of the stone — round, oval, pear, emerald — but to the precision with which the stone has been faceted: the angles, the proportions, and the symmetry of the cut relative to the ideal for that shape.
A well-cut diamond returns light through the table — the flat top facet — in a way that produces brilliance (white light return), fire (dispersion of light into spectral colours), and scintillation (the pattern of light and dark as the stone moves). A poorly cut stone leaks light through the pavilion, the bottom of the stone, and appears dull regardless of its colour or clarity.
IGI grades round brilliant cut diamonds for cut on a five-point scale: Excellent, Very Good, Good, Fair, Poor. For other shapes — ovals, pears, cushions, emerald cuts — IGI grades polish and symmetry separately, since there is no single agreed ideal for fancy shapes. Cut grade is the most important of the 4Cs for the visual performance of a diamond, and Excellent or Very Good cut grades are the minimum worth considering for a stone that will be worn.
Colour
Diamond colour is graded on a scale from D to Z, where D is completely colourless and Z carries a visible yellow or brown tint. The scale was set arbitrarily starting at D to avoid confusion with earlier systems that used A, B, and C. Each grade represents a narrow band of colour; the differences between adjacent grades are subtle and require comparison stones to detect reliably.
Colourless diamonds — D, E, F — allow the most light to pass without modification, which is why they are the most valued in white metal settings. Near-colourless stones — G, H, I, J — represent the practical sweet spot for most buyers: the colour difference from D–F is not detectable to the eye once the stone is set, and the price difference is significant. Stones graded K and below show a visible warmth that becomes more pronounced toward Z.
Lab-grown diamonds skew heavily toward the colourless end of the scale. CVD production yields a high proportion of D–F stones, which is one reason why lab-grown diamonds of fine colour grades are more accessible than their natural equivalents at the same specification.
Clarity
Clarity measures the presence of internal characteristics (inclusions) and surface features (blemishes). Most inclusions form during the crystallisation process — in natural diamonds over millions of years in the earth; in lab-grown diamonds over the weeks of CVD or HPHT growth. The IGI clarity scale runs from Flawless (FL) through Internally Flawless (IF), Very Very Slightly Included (VVS1, VVS2), Very Slightly Included (VS1, VS2), Slightly Included (SI1, SI2), to Included (I1, I2, I3).
Flawless and Internally Flawless stones have no inclusions visible under 10x magnification. VVS inclusions are extremely difficult to locate even under magnification. VS inclusions are minor and not visible to the naked eye. SI stones have inclusions visible under 10x magnification, which may or may not be visible to the naked eye depending on their position and type. Included stones have inclusions that affect transparency or brilliance.
Eye-clean is the practical threshold: a stone in which no inclusions are visible without magnification. For most buyers, VS2 or SI1 represents the rational trade-off between clarity and price. The premium for FL and IF stones is substantial, and the visual difference from VS quality is not perceptible once the stone is set and worn.
Carat weight
One carat is 0.2 grams. Carat weight is measured precisely to the hundredth of a carat — a 1.00ct stone and a 0.98ct stone differ in weight by 0.004 grams, a difference not detectable by eye but significant in price. Price per carat increases non-linearly at certain thresholds: the jump from 0.99ct to 1.00ct, or from 1.99ct to 2.00ct, carries a price premium that is a function of demand, not of any visual difference.
Carat is weight, not size. Two diamonds of the same carat weight can appear different sizes depending on their cut proportions. A well-cut stone will appear larger face-up than a deeply cut stone of the same weight, because the mass is distributed correctly rather than buried in the pavilion. This is another reason cut grade matters: a higher-cut stone of lower carat weight can appear larger and perform better than a heavier stone with a poor cut.
IGI vs GIA for lab-grown diamonds
GIA is the older institution — founded in 1931 — and has long been considered the benchmark for natural diamond certification. For much of the natural diamond market, a GIA certificate carries the strongest brand recognition.
For lab-grown diamonds, the calculus is different. In 2020, GIA began issuing lab-grown diamond reports using the same D–Z colour scale and FL–I3 clarity scale it uses for natural stones, replacing an earlier system of descriptive ranges. In 2025, GIA changed its grading system again, moving away from specific colour and clarity grades toward broader descriptors — categorising colour as "Colourless," "Near Colourless," or "Faint" and clarity as "Internally Flawless to VS" or "SI to I" rather than specific grades.
The consequence is that a GIA certificate for a lab-grown diamond no longer specifies whether a stone is D or F colour, or VS1 or VS2 clarity. For a buyer comparing stones or understanding precisely what they are purchasing, this limits the information available. IGI has maintained full D–Z and FL–I3 grading for lab-grown diamonds, providing the same granularity of information for lab-grown material as for natural stones.
For buyers who want a precise, comparable record of a stone's quality — the information that allows meaningful comparison between stones and between retailers — IGI certification for lab-grown diamonds currently provides more detail than GIA. This is why IGI has become the dominant certification standard in the lab-grown segment, and why DHARIN uses IGI across its full collection.
What the certificate does not tell you
A certificate grades a loose stone at a point in time. It does not assess the setting, the craftsmanship of the finished piece, the metal quality, or the durability of the construction. It does not constitute a valuation for insurance purposes — a separate appraisal from a qualified valuer is required for that. It does not guarantee the stone against loss or damage.
The certificate also does not tell you whether a stone is beautiful. Grading operates within defined ranges; two stones graded VS1 can look quite different depending on the nature, size, and position of their inclusions. Two stones graded G colour can appear different under different lighting conditions. The certificate is the starting point for understanding a stone — the document that establishes its identity and its place within the grading system. It is not a substitute for seeing the stone.
All DHARIN diamonds and cultivated gemstones are IGI certified. The report number is laser-inscribed on the stone. Customers can verify their certificate directly at igireport.com using the report number.
