What Is Diamond Symmetry
Diamond symmetry grades how exactly a stone's facets line up and how evenly its outline was cut. This guide explains the faults graders look for, what each grade...
What is diamond symmetry? It is a grade for how exactly a diamond's facets line up and how evenly its outline was cut. It matters because light follows those facets, so careless alignment can send some of it where you will never see it.
Symmetry usually sits next to polish on a grading report, and plenty of shoppers skim past both. For the top two grades, that is a fair call, since the difference rarely shows without magnification. Lower grades deserve a closer look, and some shapes give away a lapse much sooner than others.
Diamond symmetry describes how precisely a diamond's facets are shaped and aligned, and how even its outline is. Laboratories grade it Excellent, Very Good, Good, Fair or Poor at 10x magnification.
Excellent and Very Good look alike to most eyes. Good can be fine for many diamonds, but check the stone itself. Be more careful with Fair or Poor, and with shapes such as pear, marquise and heart, where an uneven outline is easier to spot.
Diamond symmetry, at a glance
What it is: a grade for the alignment of a diamond's facets and the evenness of its outline.
The scale: Excellent, Very Good, Good, Fair and Poor, judged at 10x magnification.
What to look for: Excellent or Very Good on a round brilliant. On a fancy shape, read the grade, then look at the outline with your own eyes.
What it does not cover: surface finish, which is polish, and overall proportions, which belong to cut.
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View Piece →What Diamond Symmetry Measures
Picture a round brilliant from above. It has 57 or 58 facets, depending on whether the point at the bottom is polished flat, and each one was placed to answer a matching facet on the other side. Symmetry records how well the cutter kept those promises. It is one part of cut, the member of the 4Cs of diamond grading most shaped by the cutter's hand.
Graders look for specific faults. These are the ones you are most likely to see named:
- Off-center table or culet. The flat top facet or the bottom point sits to one side of the stone's center line.
- Misaligned facets. Crown facets on top fail to line up with the pavilion facets beneath them, or facets that should match come out different sizes.
- An uneven outline. A round stone is slightly oval, or a fancy shape is fuller on one side than the other.
- A wavy girdle. The thin edge of the stone rises and falls, or changes thickness as it goes around.
- Extra facets and naturals. A small added facet, or a patch of the rough crystal's original surface, sits where the pattern calls for none.
Culet is the point or tiny facet at the very bottom of a diamond.
That last item overlaps with clarity, and a natural or extra facet may also appear on the plot described in understanding diamond inclusions.
Diamond Symmetry Grades, from Excellent to Poor
Most laboratories use the same five words, though each one draws its own lines between them. A grade describes how noticeable the faults are at 10x, which is not the same as how the stone looks on your hand.
| Grade | At 10x magnification | In everyday wear |
|---|---|---|
| Excellent | Very minor faults, hard to find even for a trained grader | No visible faults |
| Very Good | Minor faults that take some searching | Looks the same as Excellent to most people |
| Good | Noticeable faults, easy to see with a loupe | Usually fine on a round; a fancy outline may look slightly uneven |
| Fair | Obvious faults | May show as a lopsided outline or an off-center table |
| Poor | Prominent faults | Often visible without any magnification |
The table is a guide to the usual pattern, so treat the last column as a place to start looking. A small stone hides faults that a large one shows, and a setting can cover part of an outline.
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View Piece →Symmetry, Polish and Cut: How They Differ
These three words appear close together on a report, and they answer different questions. Symmetry asks whether the facets are in the right place. Polish asks how smooth each facet's surface is. Laboratories often call the two together the diamond's finish.
Cut is the broader grade. For a round brilliant, the overall cut grade weighs proportions and angles along with finish, which our guide to diamond cut explains in full. On GIA reports, an Excellent cut grade on a round calls for polish and symmetry of at least Very Good. You may also hear the trade phrase "triple Excellent" or "3X", which means Excellent in all three.
A diamond can earn high marks for symmetry and still disappoint. A stone cut too deep can have neatly aligned facets and still leak light. So read symmetry after you have checked the proportions, not instead of them.
How Symmetry Affects a Diamond's Look
Light enters through the top of a diamond, bounces between the pavilion facets and returns to your eye. When those facets sit where they should, the pattern of bright and dark flashes looks orderly as the stone moves. When they drift, parts of the pattern go uneven, and a badly placed facet can let light slip out the side. Our guide to what makes a diamond sparkle follows that path in more detail.
The clearest test of round symmetry is the hearts and arrows pattern. Under a special viewer, a very precisely cut round shows eight arrows from the top and eight hearts through the bottom. It is a satisfying thing to see, and it takes real precision to produce. You will not see the pattern on the hand without that viewer, though, so treat it as a bonus.
The faults you can sometimes spot unaided are the larger ones: a table that sits off to one side, a culet you can see drifting from center, or an outline that looks squashed. Lay a pair of diamond studs next to each other and even a small difference in outline gets easier to catch, because your eye has a comparison right there.
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View Piece →Why Symmetry Matters More in Some Diamond Shapes
Round brilliants forgive more, since a slight drift in one facet is surrounded by many others. Fancy shapes have a long axis, a point or a corner, and your eye checks those against each other without being asked. Fancy shapes also rarely get an overall cut grade, so polish and symmetry are the only cutting grades you are given. The diamond shapes guide covers each outline in depth. For symmetry, these are the things to check:
A dark band across a pear or marquise, called a bow tie, comes from how the stone returns light. It is a separate issue from symmetry, and a stone with a fine symmetry grade can still have one. You have to see the diamond, or a good video of it, to judge that.
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How to Read Symmetry on a Grading Report
On most full reports, you will find symmetry listed beside polish and fluorescence, a little apart from the color and clarity grades. Our walkthrough of how to read a diamond certificate shows where each line sits, and how diamond certification works explains who assigns the grade. Fluorescence has nothing to do with facet alignment, despite its place on the page; diamond fluorescence is its own subject.
Laboratory grown diamonds are graded on the same symmetry scale as mined ones, because the grade concerns the cutter's work. You can compare them directly within our lab grown diamond collection, ideally between stones graded by the same laboratory, since each one holds its boundaries a little differently.
If you cannot find symmetry on a document at all, you are probably holding a shorter report or a store description, and it is fair to ask for more.
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View Piece →How to Choose the Right Symmetry Grade
For an engagement ring you will look at every day, aim for Excellent or Very Good on the center stone. You will study that diamond more closely than any other you own, and a fancy shape deserves your own inspection on top of the grade. Our engagement rings are a good place to compare outlines side by side.
For a pair of studs, matching matters most. Look for two stones with similar outlines and similar grades, because they will be judged against each other from the moment they are on. Very Good on both will please you more than Excellent on one and Good on the other.
For a tennis bracelet or a wedding band set with many small stones, do not expect a symmetry grade at all. Small diamonds are rarely graded one by one. Judge those pieces by how evenly the row reads, and browse our diamond bracelets with that in mind.
For a budget you want to stretch, Good symmetry on a round can be a sensible place to give ground. Excellent usually costs somewhat more than Very Good for an otherwise similar stone, and that money may do more in carat weight or color. See how diamond pricing works for the wider picture, and read our diamond clarity guide before you decide.
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View Piece →Frequently Asked Questions
Does diamond symmetry matter?
Yes, though less than cut quality overall. Facet alignment affects how orderly a diamond's light pattern looks, and very low grades can show as a visibly uneven stone. The gap between Excellent and Very Good rarely shows without magnification.
Is Very Good symmetry good enough?
For most diamonds, yes. Faults at this grade take some searching at 10x, and most people cannot tell a Very Good stone from an Excellent one in normal wear. On a fancy shape, look at the outline as well as the grade.
Is Good symmetry bad?
Not necessarily. Good symmetry can look fine on a round diamond, especially a small one. Faults are easier to see at this grade, so look at the stone itself, and be more careful on a pear, marquise or heart shape.
What is the difference between polish and symmetry?
Symmetry describes where the facets are and how well they align. Polish describes how smooth their surfaces are. Together they make up a diamond's finish, and both use the same five grades.
Can you see symmetry with the naked eye?
Usually only at the lower grades. A noticeably off-center table or a lopsided outline can show without magnification, while the differences between the top grades need 10x. Size and setting change how much you can see.
Do fancy shape diamonds get a symmetry grade?
Yes. Full reports on fancy shapes usually list polish and symmetry even though they rarely give an overall cut grade. Those two grades are the main cutting information on the report, so read them closely.
Does symmetry affect a diamond's durability?
Not directly, since the grade describes alignment and outline. A very uneven girdle can leave a thin area that is more exposed to chips, so read the girdle line on the report too and ask how the setting protects that spot.
Now you know what to ask. Find the symmetry line on the report, aim for Excellent or Very Good, and look hard at the outline if you are choosing a fancy shape. Start with our diamond engagement rings or the wider fine jewelry collection, and ask our team for report details on any piece you are considering.
Choose a diamond by its report, then by your own eye.
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