How to Read an IGI or GIA Diamond Certificate as a Non Expert

Published 9 August 2026 by Rajesh Londe, 3rd generation jeweller | About the author

Every field on a diamond report, and what it means for you

This table works for any IGI or GIA report anywhere in the world. Read it once and you will never hand a certificate back and nod politely again.

Why the certificate exists at all

A grading report exists because the person selling you a diamond should not also be the person grading it. An independent gemological laboratory receives the loose stone, grades it under controlled lighting and magnification, and issues a report tied to a unique number. The Gemological Institute of America was founded in 1931 and the International Gemological Institute in 1975, and both grade to the same D to Z colour scale and the same FL to I3 clarity scale that the trade has used for decades. Neither lab is paid on the outcome of the grade, which is the whole point.

This is the part most buyers get backwards. The report is not a warranty, not a valuation and not a guarantee of beauty. It is a standardised description of one specific stone, written by someone with no stake in whether you buy it. Everything else, including the price, sits on top of that description and is set by the seller. At our four Nagpur showrooms we deal in natural diamonds. Every solitaire we sell carries its own IGI or GIA report, and we hand you the report before we quote a number, not after.

Step 1: prove the report belongs to this stone

Match three things and the paperwork question is closed: the report number printed on the certificate, the laser inscription on the diamond girdle, and the record that appears when you type that number into the lab verification tool on gia.edu or igi.org. The inscription is etched into the narrow band around the widest part of the stone and is far too small for the naked eye. You need 10x magnification, which is what a standard jeweller loupe gives you.

Do this before you discuss price, not after. It takes under two minutes and it removes the only fraud that actually matters at retail, which is a genuine report from a genuine lab paired with a different and lesser stone. If the diamond carries no inscription, that is not automatically a problem, older and smaller stones are often uninscribed. In that case ask for the stone to be weighed on a calibrated scale in front of you and check the carat weight and the millimetre measurements against the report. If either is off, stop.

Walk in and try it: at any Londe Jewellers Gold & Diamonds showroom in Nagpur we will hand you the loupe rather than looking for you. Reading your own inscription is the moment most customers stop feeling talked at.

Step 2: carat weight is mass, and it is written to two decimals

Carat weight is a measure of mass, not of how big the stone looks, and every report states it to two decimal places such as 0.72 ct or 1.03 ct. One carat is 0.2 grams. Two stones of identical carat weight can look meaningfully different across a counter, because a deep cut buries weight underneath the setting where nobody sees it, while a well proportioned stone spreads that same weight across the face.

The practical trick sits at the round numbers. Trade pricing steps up at 0.30, 0.50, 0.70, 0.90 and 1.00 carat, so a 0.96 ct stone and a 1.01 ct stone are a visual dead heat and a real gap in rupees. If your budget is fixed, ask to be shown the weights just below the next step. This is the single easiest saving available to a first time diamond buyer and no salesperson volunteers it.

Step 3: colour runs D to Z, and you cannot see most of the difference

The colour scale has 23 grades from D to Z, where D is completely colourless and Z is a light yellow you can see without training. Labs grade the stone face down against a white tray under controlled light, which is the exact opposite of how you will ever wear it. Face up, set in metal, under normal room light, the gap between neighbouring grades effectively disappears.

D to F is the colourless band and carries a premium you pay for the certificate line rather than for anything visible. G to J is the near colourless band and looks white once set, particularly in yellow gold, where the metal warms the stone anyway. K and below start showing warmth that most buyers notice. If you are buying a diamond that will sit in a gold mangalsutra or a gold ring, spending the difference between an F and a G on carat weight or cut instead is usually the better trade.

Step 4: clarity has 11 grades and the useful line is at VS2

Clarity is graded at 10x magnification on an 11 step scale: FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2 and I3. The critical thing to understand is that the grade is assigned under magnification, and you will wear the stone without magnification. Most stones graded VS2 or better are clean to the naked eye, which is the standard the trade calls eye clean.

SI1 and SI2 are where judgement starts to matter, because an SI1 with one small inclusion tucked under a prong looks identical to a VS2 on the finger, while an SI1 with a dark crystal sitting under the table does not. This is exactly what the plotting diagram is for. Never buy an SI grade on the strength of the letters alone, look at where the symbols sit on the plot and then look at the actual stone.

Step 5: cut, polish and symmetry are the grades you can actually see

Cut is the only one of the four Cs that measures human workmanship rather than an accident of geology, and it is the grade that decides whether a stone looks alive. GIA assigns a full cut grade to round brilliant diamonds only, and reports polish and symmetry for fancy shapes such as oval, pear and princess. IGI publishes a cut grade on many fancy shapes as well. So if you are looking at an oval on a GIA report and cannot find a cut grade line, nothing is missing, the lab does not issue one.

Polish describes the surface finish left by the cutter and symmetry describes how evenly the facets align, both on an Excellent to Poor scale. Treat Very Good as your floor on both. A stone with an Excellent cut, Excellent polish and Excellent symmetry at a G colour and VS2 clarity will outperform a D colour, IF clarity stone with a Fair cut in every real room you will ever stand in. If you have to spend unevenly, spend on cut.

Step 6: fluorescence and the comments line, the two fields buyers skip

Fluorescence is graded in 5 levels, None, Faint, Medium, Strong and Very Strong, and it describes whether the stone glows under ultraviolet light. On lower colour grades a Medium or Strong blue fluorescence can actually make the stone face up slightly whiter. On a high colour stone in the D to F band, Strong or Very Strong fluorescence can produce a milky or hazy look in daylight, and that stone will be priced lower for a reason. If the report says Strong, ask to see the stone outdoors before you commit.

Then read the comments line, which is where the lab records clarity characteristics that were not drawn on the plotting diagram. Phrases like clarity grade is based on clouds that are not shown are doing enormous work in that sentence. It means the thing setting the grade is a haze spread through the stone that the plot could not usefully draw. A stone with that comment can look flat and sleepy next to another stone of the same printed grade. This one line separates buyers who read the certificate from buyers who read the letters.

Step 7: the plotting diagram and the key to symbols

The plotting diagram is a map of the stone from above and below with coloured symbols showing where each clarity characteristic sits, and the key to symbols is the legend that names them. Red symbols mark internal characteristics, called inclusions, and green symbols mark external ones, called blemishes. The four names you will meet most often are feather, which is a small internal fracture, cloud, which is a cluster of tiny pinpoints, crystal, which is another mineral trapped inside, and pinpoint, which is a single tiny dot.

What you are looking for is position, not count. An inclusion at the edge of the stone will be hidden by a prong. An inclusion directly under the table, the large flat facet on top, sits in your line of sight forever. Two stones both graded SI1 with the same number of symbols can be an easy yes and an easy no purely on where those symbols sit. Ask to see the plot and the stone side by side.

How a certificate turns into the price on your invoice

The certificate sets the diamond grade, and then four separate numbers turn that grade into a rupee figure on a finished piece: the diamond value, the gold value at the day rate, the making charges, and a flat 3 percent GST on the total invoice. Our published making charge range is 8 percent to 28 percent, with plain designs at the 8 percent to 12 percent end and heavy handcrafted bridal work at the top of the band. A certificate that says nothing about any of this is doing its job, because a grading lab never states a value.

This matters more in Vidarbha than in a metro, because a lot of local diamond jewellery is hand set on Nagpuri karigari mounts where the labour content per gram of gold is genuinely high, and that labour shows up in making charges rather than in the stone. Two shops can quote the same certified stone and land a long way apart entirely on the making charge line. Ask for the making charge to be shown as its own line before you compare anything. See our making charges breakdown for Nagpur and the live gold rate for Nagpur today for the two inputs you can verify yourself before you walk in.

What the certificate does not cover, and how exchange works

A grading report covers the diamond only. It says nothing about the gold it is set in, nothing about the setting quality, and nothing about what the piece is worth on the day you bring it back. For the gold portion of a diamond piece, the document that matters is the BIS hallmark with its HUID, and for the gold value on exchange the number that matters is the deduction percentage.

Ours is 0 percent deduction on 22K and 24K gold, including jewellery originally bought from another jeweller, with purity tested in front of you and the same prevailing Nagpur rate applied to both the gold you bring in and the gold you take home. Payouts go by bank transfer or UPI, never cash. Our gold exchange policy for Nagpur sets out the full process, and the gold jewellery collection shows what the certified stones actually get set into.

Where to have your certificate read out to you in Nagpur

Bring the report and the piece to our Gokulpeth showroom at Plot no. 175, N Bazar Road, near Kumar Bakery, Gokulpeth, Nagpur, Maharashtra 440010, open 11 AM to 8:30 PM, phone +91 84460 90383. Kumar Bakery is the landmark to look for on N Bazar Road and the showroom is a few steps from it, with the west Nagpur catchment of Dharampeth, Shankar Nagar and Ramdaspeth all within a short drive.

The same reading is available at our Sitabuldi, Manish Nagar and Nandanvan showrooms, all four keeping the same 11 AM to 8:30 PM hours. You do not need to have bought the piece from us and there is no charge. Bring a certificate from any jeweller, any city, and we will read it with you. Londe Jewellers Gold & Diamonds, Golden Bonds of Trust.

Frequently asked questions