What Does IGI Certified Mean for a Lab Grown Diamond?
IGI certified means a diamond has been independently graded by the International Gemological Institute, one of the world's largest and most trusted gemological laboratories. An IGI certificate is not a jeweller's opinion. It is a graded report produced by trained gemologists under controlled laboratory conditions, using standardised equipment, with no commercial interest in what grade the stone receives.
The certificate documents everything measurable about your diamond: cut quality, colour, clarity, and carat weight — the four internationally recognised criteria known as the 4Cs. For lab grown diamonds, the certificate also specifies the growth method (CVD or HPHT) and confirms the stone's laboratory origin.
When you buy a Bellari lab grown diamond necklace, your stone comes with its individual IGI certificate. This guide explains what every section of that certificate means, which grades to look for when buying a diamond necklace specifically, and how to verify your certificate is genuine.
(explore IGI certified jewellery)
Who Is IGI?
IGI — the International Gemological Institute — was founded in Antwerp, Belgium in 1975. It is now one of the world's largest gemological laboratories, with more than 30 offices across 18 countries including Australia.
IGI has been grading lab grown diamonds since 2005 — earlier than any other major gemological laboratory. As a result, IGI developed the most specialised grading protocols for lab grown diamonds and became the global industry standard for this category. When you purchase a lab grown diamond from a fine jeweller in Australia, it is almost certainly IGI certified.
IGI grading is performed by trained gemologists who assess each stone independently, with no knowledge of other graders' assessments. Multiple gemologists grade each stone and the final grade is only assigned when there is sufficient agreement among graders. This process removes individual subjectivity from the result.
What an IGI Certificate Documents
An IGI lab grown diamond certificate contains the following sections:
Report Number
A unique number assigned to your specific diamond. This number is also laser-inscribed on the diamond's girdle (the narrow band around the widest circumference of the stone). The girdle inscription is how you match the physical stone to its paper certificate — it is a lifetime identifier for your diamond.
Report Date
The date on which the diamond was assessed at an IGI laboratory.
Shape and Cut Style
Describes the diamond's shape (round brilliant, oval, pear, emerald, etc.) and the style of faceting applied. A round brilliant has 58 facets optimised for maximum light return. Oval, pear, and emerald cuts use different facet arrangements suited to their shape.
Measurements
The precise dimensions of the diamond in millimetres: length × width × depth. For a round stone, this is diameter × depth. These measurements confirm the stone matches the certificate and help establish accurate setting specifications.
The 4Cs — Cut, Colour, Clarity, Carat
These are the four criteria on which every diamond is graded, and they determine both the stone's appearance and its value.
The 4Cs Explained for Diamond Necklace Buyers
Cut — The Most Important Factor
Cut grade ranges from Excellent → Very Good → Good → Fair → Poor. Cut is the most important of the 4Cs because it directly determines how much light the diamond reflects and how brilliant it appears to the eye. A diamond with excellent colour and clarity but a poor cut will look dull. A diamond with a modest colour grade but an Excellent cut will outshine it.
Cut grade assesses three elements:
- Proportions — the angles and ratios between the diamond's facets, which determine how light enters, bounces internally, and exits the stone
- Symmetry — how precisely the facets align and mirror each other
- Polish — the smoothness of each facet surface
For a diamond necklace: always look for Excellent or Very Good cut grade. There is no scenario in which a lower cut grade is worthwhile.
A note on cut for pendant-specific shapes: round brilliant cut grades are straightforward — Excellent is the top grade. For oval, pear, and emerald cuts, there is no universal cut grade on IGI certificates (these fancy shapes are graded on polish and symmetry separately). Instead, look for Excellent polish and Excellent symmetry, and assess the diamond's proportions — depth percentage between 60–70% and a table percentage between 55–65% are the ranges most suited to brilliant light return in pendant settings.
Colour — More Visible in a Necklace Than in a Ring
The IGI colour scale runs from D (colourless) through Z (light yellow). D, E, and F are colourless — the highest grades. G, H, and I are near-colourless, with traces of warmth detectable only by a trained eye under controlled conditions.
The colour scale:
| Grade | Classification | What it looks like |
|---|---|---|
| D | Colourless | Completely icy and bright — the rarest grade |
| E | Colourless | Virtually identical to D; trace colour detectable only in lab conditions |
| F | Colourless | Exceptional; colour difference from D/E invisible to naked eye |
| G | Near-colourless | Very slight warmth, undetectable face-up in most settings |
| H | Near-colourless | Slight warmth visible in side-by-side comparison with D–F |
| I–J | Near-colourless | Slight warmth visible, especially in larger stones |
| K–Z | Faint to light yellow | Visible warmth; generally avoided in fine jewellery |
For a diamond necklace, colour matters more than in a ring setting. In a ring, the stone is surrounded by a mount that provides visual context. In a solitaire necklace, the diamond hangs in isolation against skin — so its colour is more visible. Recommendations by metal:
- 18K white gold or platinum setting: Choose D, E, or F. The cool metal enhances the diamond's colourless appearance and any warmth in a G–H stone becomes more apparent.
- 18K yellow gold setting: G or H colour can be an excellent choice. The warm gold setting masks any trace of warmth in the diamond, allowing you to achieve a bright, brilliant appearance at a more accessible price point than D–F.
Clarity — Eye-Clean Is What Matters for a Necklace
The IGI clarity scale runs from FL (Flawless) through IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, and I3. Clarity assesses the presence of internal inclusions (internal characteristics such as crystals, feathers, or clouds within the stone) and surface blemishes, graded at 10× magnification by trained gemologists.
The clarity scale:
| Grade | Classification | Visible to naked eye? |
|---|---|---|
| FL | Flawless | No inclusions or blemishes under 10× magnification |
| IF | Internally Flawless | No internal inclusions; minor blemishes only |
| VVS1 / VVS2 | Very Very Slightly Included | Inclusions extremely difficult to see at 10× magnification |
| VS1 / VS2 | Very Slightly Included | Inclusions difficult to see at 10×; invisible to naked eye |
| SI1 / SI2 | Slightly Included | Inclusions noticeable at 10×; may or may not be eye-visible |
| I1 / I2 / I3 | Included | Inclusions visible to naked eye; affect transparency |
For a diamond necklace, VS1 or VS2 is the practical sweet spot. Here is why:
A solitaire diamond necklace is worn at chest height. The viewing distance when someone admires your necklace is 30–50 cm or more. At that distance, VS1 and VS2 inclusions — which are difficult to see even under 10× magnification — are completely invisible. A VS1 stone and a FL (Flawless) stone look identical to anyone looking at your necklace.
This means paying significantly more for VVS1, VVS2, or FL clarity in a necklace provides no visible benefit over VS1 or VS2. The budget saved by choosing VS1 over FL is better applied to a higher carat weight, a better cut grade, or a superior colour — all of which produce visible improvements to how your necklace looks.
Avoid SI2 and below for a solitaire necklace. At SI2, inclusions begin to approach eye-visibility, and in a pendant setting — where the stone is the sole focal point — visible inclusions can affect the stone's appearance.
Practical clarity recommendation by necklace type:
| Necklace type | Recommended clarity |
|---|---|
| Round brilliant solitaire | VS1 or VS2 |
| Oval solitaire | VS1 or VS2 |
| Pear solitaire | VS1 (avoid inclusions near the tip) |
| Emerald cut | VVS2 or VS1 (step-cut facets show inclusions more readily) |
Note on emerald cut clarity: The emerald cut's long, parallel step facets create a hall-of-mirrors effect that makes the interior of the diamond more visible than brilliant cuts. Inclusions that are undetectable in a round or oval stone can become more visible in an emerald cut. For this reason, we recommend VS1 or VVS2 clarity for an emerald cut solitaire necklace.
Carat Weight — Size and Appearance
Carat is the unit of weight for diamonds. One carat equals 0.2 grams. Carat weight does not directly equal size — two diamonds of the same carat weight can appear different sizes depending on their cut proportions and shape.
For reference, approximate face-up diameter of round diamonds at common carat weights:
| Carat weight | Approximate diameter (round brilliant) |
|---|---|
| 0.25 ct | ~4.1 mm |
| 0.50 ct | ~5.2 mm |
| 0.75 ct | ~5.8 mm |
| 1.00 ct | ~6.5 mm |
| 1.25 ct | ~7.0 mm |
| 1.50 ct | ~7.4 mm |
Fancy shapes — oval, pear, emerald — often appear larger face-up than a round brilliant of the same carat weight because their elongated shape covers more surface area. A 0.75 ct oval can appear similar in visual presence to a 1.00 ct round brilliant, which is part of the appeal of these shapes for necklace buyers.
Additional Certificate Fields
Polish and Symmetry
Graded Excellent, Very Good, Good, Fair, or Poor — these assess the smoothness of each facet surface and the precision of facet alignment. For fancy shapes (oval, pear, emerald) where no overall cut grade is issued, polish and symmetry are the primary precision indicators. Look for Excellent or Very Good in both.
Fluorescence
Fluorescence describes how a diamond reacts under ultraviolet light — emitting a visible glow, usually blue. Fluorescence is graded None, Faint, Medium, Strong, or Very Strong.
For necklace buyers: None to Faint fluorescence is ideal. Strong or Very Strong fluorescence can occasionally cause a stone to appear milky or hazy in bright sunlight, particularly in diamonds with high clarity grades. In lower colour grades (H–I), Medium blue fluorescence can actually make the stone appear whiter — a useful effect in yellow gold settings.
Growth Type (Lab Grown Diamond Specific)
The IGI certificate for a lab grown diamond specifies whether it was produced using CVD (Chemical Vapour Deposition) or HPHT (High Pressure High Temperature). Both methods produce genuine diamonds — the growth type has no practical impact on the finished stone's appearance or wearability, but it is disclosed for transparency.
How to Verify Your IGI Certificate Is Genuine
Every IGI certified diamond can be verified directly on the IGI website. Here is the process:
- Locate the Report Number on your IGI certificate — it appears prominently at the top of the document
- Visit igi.org and navigate to the Report Check tool (direct URL: igi.org/reports/verify-your-report)
- Enter your report number in the verification field
- The IGI database will return the stone's graded details — cut, colour, clarity, carat, measurements, and a clarity diagram
- Compare the returned details to your printed or digital certificate — they must match exactly
- Ask your jeweller to show you the girdle inscription under a loupe — the laser-inscribed number must match the Report Number on the certificate
If any detail does not match, or if the report number does not appear in the IGI database, the certificate is not authentic.
Bellari provides the IGI report number with every order, and the certificate can be verified immediately upon receipt of your piece.
IGI vs GIA — Which Is Better for Lab Grown Diamonds?
Both are independent, reputable gemological laboratories. The differences are:
| IGI | GIA | |
|---|---|---|
| Founded | 1975 (Antwerp) | 1931 (USA) |
| Lab grown diamonds | Since 2005 — global leader | Full 4Cs reports since late 2020 |
| Market position | Dominant for lab grown diamonds globally | Dominant for natural mined diamonds |
| Grading stringency | Slightly less strict than GIA | Most conservative grader in the industry |
| Accepted in Australia | Yes — industry standard | Yes — widely accepted |
| Price | Certificates generally lower cost | Certificates generally higher cost |
Practical guidance for Australia: For lab grown diamonds, IGI certification is the industry standard. The vast majority of lab grown diamonds sold by Australian fine jewellers are IGI certified. GIA certification is equally credible but less common in this category. Either certificate provides reliable, independent assurance of your diamond's quality.
Be aware that IGI grading has historically been considered marginally less conservative than GIA — some industry participants suggest applying a one-grade buffer when comparing IGI grades to GIA grades (e.g., an IGI VS1 may be closer to a GIA VS2). This is worth knowing if you are comparing stones across different certifications, but it does not affect the absolute quality of the stone you are purchasing from Bellari.
Why IGI Certification Matters When You Buy a Diamond Necklace
Without independent certification, you are relying entirely on a jeweller's word about a diamond's quality. A jeweller has a financial interest in the sale. An IGI gemologist does not.
An IGI certificate gives you:
Objective quality documentation. Cut, colour, clarity, and carat weight assessed by independent gemologists using standardised criteria and equipment. Not a sales description — a graded report.
Verified identity. The laser-inscribed girdle number matches your certificate to your specific stone. This is how you confirm the stone in your necklace is the stone described on the certificate.
Comparative standardisation. You can compare diamonds from different jewellers on a level playing field using the same grading scale.
Insurance support. Australian insurers use your IGI certificate when establishing the replacement value of your diamond jewellery. Keep your certificate — you will need it if you ever make a claim.
Lifetime reference. Your IGI certificate permanently documents your stone. Decades from now, if your diamond is reset, resized, or passed down, the certificate travels with it.
Bellari's IGI Certified Diamond Necklace Collection
Every lab grown diamond in Bellari's solitaire necklace collection is independently IGI certified. Each piece is made to order in Sydney in solid 18K gold — not gold plated — with your IGI certificate included with your order.
The collection spans four cuts, each available in 18K yellow gold and 18K white gold.
Round Brilliant Cut
The round brilliant is the most light-efficient diamond cut ever developed. Its 58 precisely calculated facets are engineered for maximum light return — producing the bright, white sparkle that defines the classic diamond look. In a solitaire necklace setting, it catches light from every direction.
- Round Brilliant Diamond Necklace — 18K Yellow Gold
- Round Brilliant Diamond Necklace — 18K White Gold
Oval Cut
The oval cut elongates on the neckline and appears larger face-up than its carat weight suggests. It retains most of the brilliance of a round brilliant while offering a more distinctive, modern silhouette. Recommended clarity for oval: VS1 or VS2.
Pear Cut
The pear — or teardrop — combines the pointed brilliance of a round cut with a tapering tip that hangs naturally at the base of a pendant. When worn as a necklace, the tip orients downward, creating an elegantly elongating line. For pear cuts: choose VS1 clarity and avoid inclusions at or near the tip, where the stone is more vulnerable.
Emerald Cut
The emerald cut is a step-cut design — long, parallel facets rather than brilliant facets — that produces a hall-of-mirrors effect. It is architectural and understated, showing the diamond's clarity and depth rather than maximising sparkle. Emerald cuts reward higher clarity grades (VS1 or VVS2) because the step facets allow deeper visual access to the stone's interior.
For a full comparison of all four cuts including how they wear on the neckline, read our Lab Grown Diamond Solitaire Necklace Guide.
Recommended IGI Grades at a Glance Diamond Necklace Buyers
| Grade | Recommendation for necklace |
|---|---|
| Cut | Excellent (or Very Good minimum) |
| Colour — white gold setting | D, E, or F |
| Colour — yellow gold setting | G or H (excellent value; yellow gold masks warmth) |
| Clarity — round, oval, pear | VS1 or VS2 (eye-clean at all wearing distances) |
| Clarity — emerald cut | VS1 or VVS2 (step facets reward higher clarity) |
| Polish | Excellent |
| Symmetry | Excellent |
| Fluorescence | None to Faint |
This table represents the practical sweet spot — grades that produce a beautiful, visually flawless necklace diamond without unnecessary spending on microscopic differences that are invisible in a pendant setting.
Final thoughts
IGI certification is the independent grading standard for lab grown diamonds in Australia. It means a trained gemologist — not a jeweller with a sales interest — has assessed your specific stone's cut, colour, clarity, and carat weight using standardised equipment and criteria, and documented the results on a certificate you can verify online.
For a diamond necklace, the practical priorities are: Excellent cut, D–F colour in white gold or G–H in yellow gold, VS1 or VS2 clarity (or VS1/VVS2 for emerald cut), and Excellent polish and symmetry. These grades produce a diamond that is visually exceptional in a pendant setting while representing genuine value.
Every Bellari lab grown diamond necklace is independently IGI certified. Your certificate is included with your order, the report number is laser-inscribed on your stone's girdle, and it can be verified directly at igi.org at any time.
If you are new to lab grown diamonds and want to understand the broader landscape — what they are, how they compare to mined diamonds, and whether they are worth buying — read our guide: Are Lab Grown Diamonds Real? Everything Australians Are Asking in 2026.
Frequently Asked Questions
What does IGI certified mean? IGI certified means a diamond has been independently graded by the International Gemological Institute — one of the world's largest gemological laboratories. The IGI certificate documents the diamond's cut, colour, clarity, and carat weight using standardised criteria, assessed by trained gemologists with no commercial interest in the outcome.
Is IGI certification trustworthy? Yes. IGI has been grading diamonds since 1975 and has specialised in lab grown diamond certification since 2005 — longer than any other major laboratory. It is the most widely used certification body for lab grown diamonds in Australia and globally.
What is the difference between IGI and GIA certification? Both are reputable. GIA is considered the most conservative grader and historically dominant for mined diamonds. IGI is the global leader for lab grown diamond certification. For lab grown diamonds sold in Australia, IGI is the industry standard. GIA grades are generally slightly stricter than IGI grades on the same stone.
What IGI colour grade should I choose for a diamond necklace? In a white gold setting, D, E, or F colour. In a yellow gold setting, G or H colour — the warm metal masks any trace of warmth in the stone and provides excellent value. For a solitaire necklace worn against skin, colour is more visible than in a ring, so staying D–H is recommended.
What IGI clarity grade should I choose for a diamond necklace? VS1 or VS2 for round brilliant, oval, and pear cuts. VS1 or VVS2 for emerald cuts, which reveal the interior of the stone more clearly due to their step-cut facets. FL and IF are unnecessary for a necklace — the visual difference from VS1/VS2 is imperceptible at wearing distance.
What does the IGI cut grade mean? Cut grade assesses the diamond's proportions, symmetry, and polish — the factors that determine how much light the diamond reflects. It ranges from Excellent to Poor. Cut is the most important of the 4Cs for brilliance. Always choose Excellent or Very Good cut.
How do I verify my IGI certificate is genuine? Visit igi.org, use the Report Check tool, and enter your certificate's Report Number. The IGI database will return your stone's graded details. Match these to your certificate and to the laser-inscribed number on the diamond's girdle.
What does a lab grown diamond IGI certificate include? Report number, date, stone shape, measurements, cut grade, colour grade, clarity grade, carat weight, polish grade, symmetry grade, fluorescence, growth type (CVD or HPHT), clarity diagram, and laser inscription number.
Does IGI certify lab grown diamonds the same way as mined diamonds? Yes — using the same 4Cs scale. IGI lab grown diamond certificates additionally specify the growth method (CVD or HPHT) and confirm laboratory origin.
Why does IGI certification matter when buying a diamond necklace? It provides objective, independent documentation of your diamond's quality — not a jeweller's sales description. It enables verified quality comparison across different jewellers, supports insurance valuation, and permanently identifies your specific stone via the girdle laser inscription.
Can I insure a lab grown diamond necklace in Australia? Yes. Australian insurers cover lab grown diamond jewellery. Your IGI certificate is a key document for establishing replacement value. Keep it alongside a current jewellery valuation from a licensed Australian valuer.
Does Bellari provide IGI certificates with diamond necklace purchases? Yes. Every Bellari lab grown diamond solitaire necklace is independently IGI certified. Your certificate is included with your order and can be verified at igi.org using the report number laser-inscribed on your stone.
