When I sit down with a client to choose a diamond, carat gets looked at first.
Then colour. Then clarity.Cut can get about three seconds.That's usually where I slow things down.
Knowing how to read a diamond grading report gives you a much better idea of what you're actually comparing, especially when two diamonds look similar on paper.
There's also one thing worth clearing up early: diamond shape and cut quality are different things.
Round, oval, pear, cushion, emerald, radiant, marquise and princess describe the shape or cutting style of the diamond. Cut quality is about the proportions, facet arrangement and craftsmanship that influence how that diamond looks and handles light.
And the way I assess that changes depending on the shape.
Before Anything Else, Confirm the Report Matches the Stone
Before I start comparing quality or value, I check that I'm looking at the correct stone.
On a GIA diamond grading report, I'll look at the report number, shape and cutting style, carat weight and measurements. Some diamonds also carry a microscopic laser inscription on the girdle with their GIA report number.
You can enter the report number into GIA Report Check to confirm that the report details match the information held in GIA's database. That confirms the report record. I still compare the actual diamond with its measurements and inscription where applicable.
It takes very little time. I always start there.
For a Round Brilliant, Cut Is the First Grade I Look At
If I'm looking at a standard round brilliant, the Cut grade is one of the first things I want to see.
GIA grades the cut of eligible round brilliants from Excellent to Poor. Its system considers brightness, fire and scintillation, along with weight ratio, durability, polish and symmetry.
This matters because carat tells me how much a diamond weighs. It doesn't tell me how lively it will look.
For many clients, I would rather protect the budget for a well-cut round diamond than spend significantly more moving up a clarity grade when the difference is only visible under magnification.
An Excellent Cut grade is a useful place to start. Then I want to see the stone.
There is still variation within a Cut grade, and personal preference matters too. GIA itself notes that each grade represents a range of proportion sets and appearances.
So I use the grade to narrow things down. Then I look.
Fancy Shapes Need a Different Kind of Reading
This is where choosing a diamond becomes more interesting.
GIA currently does not give an overall Cut grade to fancy-shaped diamonds such as oval, pear, marquise, cushion, emerald and princess cuts. Their facet patterns, proportions and visual behaviour vary too much for the round-brilliant grading system to be applied to them.
So if I'm sourcing a fancy shape, I'm reading several things together: measurements and proportions, length-to-width ratio, polish, symmetry, girdle, outline, clarity characteristics, and how the stone actually looks when it moves.
Different shapes make me look for different things.
With an oval, I want to see its outline and how the light behaves through the centre. Some show a noticeable bow-tie, a darker area across the middle, so I want to see whether that adds character or becomes distracting.
With a pear, I'm looking at the shoulders, point, symmetry and overall balance as well as the bow-tie area.
With marquise diamonds, symmetry and the relationship between the length and width can completely change the feeling of the stone.
With cushion and radiant cuts, there can be a surprising amount of visual difference between stones carrying the same basic shape description. I want to see the pattern of brightness and contrast across the whole diamond.
With emerald and asscher cuts, the step facets make the internal pattern much more obvious. Clarity, proportions and symmetry deserve close attention here.
With a princess cut, I'm also thinking ahead to the setting because its corners need appropriate protection.
This is why I'm careful with online charts that tell you there is one perfect ratio for every fancy shape. The measurements are useful. The actual diamond still needs to look good.
Carat Weight Only Tells Me Part of the Story
Two diamonds can weigh exactly one carat and look quite different once they're on your hand.
That's why I always read the measurements alongside the carat weight. A diamond may carry more of its weight through its depth. Another may have more face-up spread.
With fancy shapes, those measurements also tell me about proportion. Take two oval diamonds at the same carat weight. One might be longer and slimmer. The other might have a fuller, softer outline.
Neither automatically wins.
I want to know which proportion works for the stone, the ring and the person wearing it.
The same thinking applies to pears, cushions, radiants, emerald cuts and marquises. For a bespoke engagement ring, those dimensions also affect the design around the diamond: the setting, band proportions and how the finished ring will sit on the finger.
Clarity Is a Map, Not Just a Grade
If the GIA report includes a clarity plot, I read it almost like a map of the diamond.
GIA assesses clarity using the size, nature, position, relief and number of clarity characteristics under 10x magnification.
The grade matters. Where the inclusions are matters too.
If a characteristic sits underneath the centre of the table, I want to know how visible it is face-up. If something is closer to the edge or reaches the surface, I'll look carefully at its position and consider whether it has any implications for durability or the eventual setting.
I'm also interested in what the client can actually see.
A diamond can have a lower clarity grade and still look very clean without magnification. Depending on the stone and the nature of its inclusions, that can be a very sensible place to use the budget.
This is why I don't choose clarity from the letters alone. I look through the loupe. Then I put the loupe down and look again.
Polish and Symmetry Are Worth the Extra Few Seconds
These two lines are easy to skip.
I don't.
Polish describes the quality of the finished facet surfaces. Symmetry considers the exactness of the diamond's shape and the placement and alignment of its facets. For eligible round brilliants, both contribute to GIA's overall Cut assessment. They are also useful information when I'm looking at fancy shapes.
With a fancy shape, I pay particular attention to the outline myself. Does an oval look balanced? Are the two sides of a pear working together? Do the steps of an emerald cut create a pleasing pattern?
Those are things I want to see, rather than assume from the report.
Fluorescence Is an Identifier, Not a Verdict
Fluorescence is another line people see on a GIA report and immediately wonder whether it is good or bad.
I wouldn't treat it that way.
GIA describes fluorescence intensity as None, Faint, Medium, Strong or Very Strong. It is an identifying characteristic rather than one of the 4Cs. GIA's research found that fluorescence has no widely noticeable effect on appearance for the overwhelming majority of diamonds. Very strong fluorescence can cause a hazy or oily appearance in rare cases.
So if fluorescence is present, I simply want to see the diamond in different lighting.
That answers most questions more quickly than the report can.
Then I Put the Report Down
Once I've read everything, I go back to the actual diamond.
This is the most important part of the process.
I look at it face-up. I tilt it. I move it around. I look at it in different lighting. I'm watching the brightness, the pattern of light and dark, the shape, any visible inclusions and how the whole stone feels when it's moving.
And if I'm sourcing it for a bespoke engagement ring, I'm already thinking about the design.
How will this proportion sit on the hand? How high does the diamond need to sit? How do I want to protect the corners or point? Is there something about this particular stone that could influence the setting?
A diamond grading report gives me the information I need to ask those questions.
Then I need the diamond in front of me. That combination is what I trust.
Thinking About a Diamond Commission?
If you're comparing diamonds for a bespoke engagement ring and would like a second opinion on a report, or want to talk through what to look for before you start sourcing, I'd love to welcome you into your private consultation and let's start the ideas there.
