What an IGI Certified Diamond Means | ARKH

What IGI certification actually means — reading the report behind your diamond

In plain terms: An IGI certificate is an independent lab's record of exactly what your diamond is — its cut, colour, clarity, carat and origin. It verifies the stone; it doesn't set the price. Don't buy a diamond, labgrown or natural, without one from IGI or GIA.

A diamond certificate is the one document in the box most people never actually read. They check the carat weight, recognise nothing else, and file it away. That is a missed opportunity, because the certificate is the only objective record of what you bought, and learning to read it takes about five minutes. By the end of this article you will know what IGI is, what its report verifies, how it compares to GIA, and how to read the grades that decide a diamond's price. You will be able to look at any certified stone — ours or anyone else's — and understand what you are holding. If you are still weighing up the stone itself, our companion guide on lab-grown versus mined diamonds covers that decision; this one is about the paperwork that should come with either.

What IGI is

IGI is the International Gemological Institute, founded in Antwerp in 1975 and now one of the largest independent gem-grading laboratories in the world. The word that matters there is independent. IGI does not mine, buy, sell, or set diamonds. Its only job is to examine a stone and report its characteristics. Because it has no stake in whether you buy, its assessment is impartial — which is precisely what makes it worth something. In the 25 years my family has worked with diamonds, the certificate was always the part of the transaction we treated as non-negotiable. A stone without an independent report is a stone you are taking on trust, and trust is not a grading standard. A lab report replaces the seller's word with a measurement.

What an IGI report actually tells you

The report records the measurable facts about one specific stone. Most of it is the four characteristics known as the 4Cs — carat weight, cut, colour, and clarity — each assessed against a defined scale under controlled lighting and magnification. Alongside those, the report notes the stone's exact measurements, its proportions, polish and symmetry, any fluorescence, and a unique report number. For a lab-grown diamond, IGI also states the growth method and confirms, in plain language, that the stone is laboratory-grown rather than mined. The report number is worth dwelling on, because it is what makes the document yours rather than generic. It ties one physical stone to one set of grades, and on larger diamonds it is often laserinscribed onto the girdle so the stone and its paperwork can never be quietly separated. If you ever sell, insure, or revalue the piece, that number is the thread that proves the diamond in front of a valuer is the diamond on the report. Here is the honest limit of what a certificate does: it grades a diamond, it does not value it. It tells you what the stone is, not what you should pay for it. Two diamonds with identical grades on paper can still look slightly different in person, because grading captures most of a stone's quality but not every nuance of how it handles light. The report is the floor of an informed decision, not the whole of it. Seeing the stone still matters.

The grades that move the price

Of the 4Cs, cut has the largest effect on how a diamond actually looks — it governs how the stone returns light, which is what most people mean when they say a diamond has life. Colour is graded from D, which is colourless, down the alphabet as faint warmth appears. Clarity describes the tiny internal characteristics every diamond has, from flawless down to grades where inclusions are visible to the eye. Carat is simply weight, not size, though the two are related. A well-cut stone a fraction smaller will often outshine a larger one that has been cut for weight rather than beauty.

IGI versus GIA

Both IGI and GIA are reputable international laboratories, and a stone certified by either is a stone with credible, independent grading behind it. GIA, the Gemological Institute of America, was founded in 1931 and is the older reference; it is widely regarded as the strictest benchmark for natural diamonds, and it developed the 4Cs framework the whole industry now uses. IGI has become the dominant laboratory for lab-grown diamonds and grades a very large share of the world's certified lab stones. For lab-grown, IGI is the standard most of the trade works to, which is why it is our default at ARKH. You will occasionally hear debate about small differences in how strictly each lab grades a particular colour or clarity band. It is a fair conversation to have with whoever is selling you the stone, but it should not worry you: both labs are credible, and either certificate is one you can rely on.

How ARKH handles certification

Every Radiance diamond over 1 carat ships with its original IGI certificate, with GIA available on request. Diamonds under 1 carat ship with an ARKH specification card that records the same details — cut, colour, clarity, carat and origin — for the stone you have chosen. Whichever you receive, it is presented in the pocket of the Radiance box at delivery, with your piece. The reason small stones come with a spec card rather than a full lab report is plainly economic, and we would rather explain it than dress it up. Individually certifying a sub-1-carat stone can add a meaningful cost relative to the stone itself, and that cost would land on you for a document that mostly restates what the card already tells you. For larger stones, where the certificate genuinely protects the value of the purchase, the original report is included as a matter of course. If you would prefer full certification on a smaller stone, we can arrange it — just ask. None of this is a flourish we invented for marketing. My family worked with mined diamonds for 25 years and treated the certificate as sacred; I carried that habit into ARKH unchanged. The stones are different now. The standard around them is not.

How to use your certificate once you have it

• Check that the report number on the certificate matches any inscription on the stone's girdle, where present, and that the recorded measurements match your diamond.
• Keep it. Your certificate is what an insurer or valuer will ask for, and replacing a lost report is slow and sometimes impossible.
• Use it to compare like with like. When two stones are quoted at different prices, the certificates tell you whether you are comparing equivalent diamonds or being shown a cheaper grade.
• Never accept a diamond — lab-grown or natural — without a certificate from IGI or GIA. If a seller cannot produce one, that is your answer. Walk away.

Where to start

If you would like to see certified stones in person and have someone read the report with you, line by line, the easiest place to begin is a free consultation. It is a 30-minute conversation — in Melbourne, or over WhatsApp or Zoom anywhere in Australia and beyond — where we show you stones at different grades and price points and explain what each certificate is telling you. No commitment, and no pressure to decide on the day.

If you would rather look first, you can browse our current Radiance rings and the wider Radiance collection. Every stone over 1 carat comes with its IGI certificate in the box, so you will always know exactly what you are wearing.