The 4C framework was built to describe colorless round brilliants. Almost nothing we cut is one. This page covers the standard language, then covers what to look at once that language runs out- proportion, culet, spread, and the way a stone was actually made.
GIA built the 4Cs to describe one thing accurately: a colorless modern round brilliant. IGI grades our stones on the same scale and we publish it on every one. It is a real, useful language and we are not interested in arguing with it. It also runs out early on the goods we make, and what it stops measuring is the part we compete on.
A report grades what a stone is. It does not grade how it was cut, or why it was cut that way.
Cut grade measures proportion, symmetry, and polish against a reference model. Excellent means the stone matches that model closely. The grade exists for the round brilliant and, in a limited form, for a few other modern shapes.
At the bench No cut grade exists for a rose cut, an old mine, an old European, or a hexagon step cut. The report gives you shape and cutting style, then stops. Read crown height, pavilion depth, culet size, facet junctions, and outline symmetry instead. Most historic cuts in lab material are cut to hold weight, and the proportions go wrong in the same place every time.D through Z, colorless to light. Lab-grown stones are graded on the same scale by the same method. Below Z the stone is graded as fancy color on a separate scale.
At the bench Nearly all lab production is grown toward colorless, because colorless is what gets ordered. Rough that comes out warm is usually treated back toward white. We buy that rough untreated and cut it as champagne. It is the same carbon, left alone.FL through I3, measured by what is visible under 10x magnification. The scale assumes a single direction of travel: fewer inclusions, higher grade, higher price.
At the bench On a salt and pepper stone that assumption inverts. The inclusions are the stone. Carbon does not grow that way by accident and it does not grow that way to order unless someone asks for it. We asked for it. What matters then is pattern, density, and where the inclusions sit relative to the table.A unit of weight. One carat is 200 milligrams. Weight is not size: two stones of identical weight can differ by more than a millimeter across the face depending on how deep they are cut.
At the bench Lab goods get accused of facing up small, and on a deep modern cut that is fair. Old mine and rose proportions spread instead. Every stone here is listed with face-up millimeter dimensions next to the weight, so you are buying a size rather than a number.We cut historic proportions in new carbon, in our own factory in Surat, in small batches. We did not invent most of these shapes and we do not say we did. What is unusual is that almost nobody runs them in lab material, and the few who do cut them to save weight rather than to get the proportion right. Each card below states what is ours and what is not.
Cushion outline, high crown, small table, open culet. The ancestor of the modern cushion. An old mine wastes weight on purpose- that is the whole point, and it is why almost nobody cuts one in lab carbon.
Round outline, high crown, deep pavilion, a culet you can see straight down into. Chunky facets, slower movement, more shadow. Modern factories skip it because the yield is poor.
Flat back, domed crown, three to twenty-four triangular facets, no pavilion at all. The dome has to be built correctly or the stone reads flat and glassy. Most lab rose cuts are too shallow.
Long parallel facets, cut corners, no crushed ice. Emerald, asscher, baguette, and the hexagon, octagon, and kite outlines we run. A step cut hides nothing- the make and the clarity are both fully on show.
Hexagons, kites, shields, lozenges, trapezoids. Outlines developed here rather than inherited, then faceted as step or rose. Cut because nobody was cutting them, and now cut in carbon for the same reason.
Not a cut but a material. Black and white inclusions running through the stone, read as pattern rather than as fault. Originated as a category in natural stones and then made for the first time in lab carbon.
In a mined stone, color is a fact of geology. In lab carbon it is a choice made in the growth run and then, usually, a second choice made afterward in treatment. Almost the entire category is aimed at D to F because that is the order book. We buy against it. What follows is the range we cut, from colorless through to material most factories would reject.
Nobody grows carbon like this on purpose. We asked for it.
The top of the standard scale and the default target of the whole lab category. We cut it, and it is the correct choice when the design calls for a white stone and nothing else.
Color detectable by a trained eye against a master set, not across a table. Reads white in most settings and stays white in yellow gold.
A visible ivory cast. On a deep historic cut the warmth pools in the pavilion and becomes part of how the stone reads rather than a compromise on the grade.
Carbon that formed warm and was left untreated. Rare in lab production because the standard response is to treat it back toward white. We buy the rough as it comes out and cut it as it is.
Cool, smoky, sitting outside the D to Z ladder entirely. Reads silver in daylight and closes down to graphite in shadow. Works where a white stone would be too loud.
Black and white inclusion through the body of the stone. No two runs produce the same pattern, so no two stones repeat. Judged on distribution, not on absence.
In a mined diamond an inclusion is a geological accident, a record of pressure and time. In lab carbon it is a record of a growth run: how fast, how hot, what the seed did, what was in the chamber. Same optical result, different cause, and worth being straight about rather than dressing up.
A trained grader can read the difference under magnification, which is one of the reasons lab material is identifiable in the first place. We would rather explain that than avoid the subject.
The first lab-grown salt and pepper diamond was ours. The same hands cut our natural goods.
For salt and pepper, grey, and heavily included material, the clarity scale does not describe anything useful. Read the stone on pattern, density, distribution, and whether the inclusion sits under the table where you will look at it or off in the pavilion where you will not.
An inclusion that arrived by accident and one that arrived because somebody asked for it look identical in the stone. Only one of them can be repeated on request.
Nothing visible at 10x. Relevant for large colorless goods where the premium is real, and largely irrelevant to everything else on this page.
Extremely difficult to see at 10x. Invisible to the eye in every case. The grade most of our colorless step cuts sit in.
Visible under magnification, not to the eye. On a step cut this is where placement starts to matter more than the grade itself.
Noticeable under magnification and sometimes to the eye, depending on type and position. Check placement before the grade.
The ladder above stops working here. A stone with a hundred inclusions is not a failed stone, it is a different product. Graded by eye, by pattern, and by us.
The International Gemological Institute grades the majority of the world's lab-grown diamonds and is the standard reference for the material. Our cut goods are IGI certified and laser inscribed with the report number on the girdle, so the paper and the stone stay attached to each other.
The report gives you shape and cutting style, measurements, carat weight, color, clarity, polish, symmetry, fluorescence, and growth method. That is a complete description of the material. It is not a description of the make.
Read the report for what it is good at- verifying that the stone is what we say it is- and read the millimeter dimensions, the culet, and the photographs for everything else.
Browse certified stones →There is no cut grade for a rose cut, an old mine, an old European, a hexagon, or a kite. There is no measure of how well a historic proportion has been executed. There is no useful clarity grade for a salt and pepper stone. Everything that separates one cutter from another sits in that gap.
Every IGI lab-grown report states how the stone was grown and identifies it as laboratory-grown on the face of the document. Nothing about the origin of the material is left to be discovered later.
The report number is inscribed on the girdle and readable under magnification. It is how you confirm that the stone in front of you is the stone on the certificate, which matters most on unusual shapes that cannot be matched by outline alone.
Depth and table percentages on an old mine or old European will look wrong measured against round brilliant norms. High crown, deep pavilion, small table, open culet. That is the cut performing correctly, not a fault in the make.
We do not source and resell, so there is no back catalogue to search through. Either the stone has been cut, in which case it is on the site, or it has not been cut, in which case it can be.
Small runs, cut and listed as they finish. When a stone goes it does not come back, because the next run is different rough and a different pattern. You are looking at the actual stone, photographed and measured, not a category.
Shape, outline, proportion, culet, faceting style, color, inclusion density. All of it is open, and all of it happens in our own factory rather than at a broker's. Longer lead time, and the only route to a shape nobody stocks.
If you are sourcing for a client, building a line, or working out whether a proportion will do what you need it to do, talk to the people who made the stone. Trade accounts and trade pricing are open.
Every stone has a story. This one hasn't started.
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