Diamond cut explained: how to choose a sparkling diamond
Cut quality describes how a diamond’s proportions and finish affect its brightness and sparkle. If you are choosing a natural round brilliant, GIA Excellent is a useful starting point. Then compare the actual diamonds: the same grade can include different looks. For ovals, pears, emerald cuts and other non-round shapes, check which cut information the report provides and view the stone in motion.
Cut quality is different from diamond shape
Round, oval and pear describe a diamond’s outline. Cut quality concerns how its facets—the small polished surfaces—work together. Two diamonds of the same shape and carat weight can look quite different.
If sparkle matters to you, give cut serious attention before paying for higher colour or clarity grades. Those grades describe other qualities; they cannot compensate for unattractive light performance. GIA’s introduction to cut.
The three things you see when a diamond sparkles
| What you notice | The jeweller’s term | What it means |
|---|---|---|
| White brightness | Brilliance or brightness | White light reflected from the diamond’s surface and interior. |
| Flashes of rainbow colour | Fire | White light separating into rainbow colours. |
| Flashes as the stone moves | Scintillation | Sparkle and the changing pattern of bright and dark areas. |
Some contrast is essential: a lively diamond is not uniformly white. Lighting also changes what you see. Compare stones in ordinary indoor light and softer daylight as well as under jewellery spotlights. GIA on cut and appearance; GIA on lighting.
More balanced appearance
Dominant dark area
How to read the GIA cut scale
For standard natural round brilliant diamonds in the D–Z colour range, GIA’s overall cut grades run from Excellent to Very Good, Good, Fair and Poor. The assessment considers appearance, proportions, durability and craftsmanship. It is not a simple percentage of light returned. GIA’s cut-grade guide.
Excellent is a sensible place to start a round-diamond shortlist. Very Good is still worth considering. GIA’s examples show that a Very Good diamond can look comparable from above to an Excellent one, with its grade limited by extra weight relative to its diameter. Ask what limited the grade, then judge the individual stone. GIA’s cut-grade examples.
Read polish and symmetry separately. Polish assesses the finish of the facet surfaces; symmetry assesses the precision of the shape and facet placement. Excellent overall cut does not require both finish grades to be Excellent.
Triple Excellent, or Triple X, means Excellent cut, polish and symmetry on a GIA round-brilliant report. It is not an extra cut grade above Excellent. GIA on Triple Excellent.
Diamond anatomy: why the proportions matter
The table is the large top facet. The girdle is the edge around the stone; the crown sits above it and the pavilion below. A culet is a small facet at the bottom, when present.
Table size, depth and crown and pavilion angles interact. A table percentage by itself cannot identify a beautiful diamond, and there is no single table-and-depth recipe that works for every shape. GIA’s proportion guidance.
Also compare the measurements in millimetres. Extra weight held in depth or a thick girdle may add carats without adding much visible size. A larger carat number does not automatically mean a larger-looking diamond. GIA on proportions and size.
Ovals, pears and emerald cuts need a different approach
Non-round diamonds are often called fancy shapes. Ordinary GIA reports do not give them the overall Excellent–Poor cut grade used for standard round brilliants. If a listing says “EX”, ask which assessment the label refers to and check the report.
Other assessments exist. IGI offers optional fancy-shape cut grading, while GIA offers a separate AGS Ideal report for qualifying diamonds, including certain fancy shapes. Check which assessment you are comparing. IGI’s grading process; GIA’s AGS Ideal report.
For elongated shapes, watch how light travels across the centre as the diamond tilts. Ovals can show a bow tie, a darker band across the middle. Its visibility changes with viewing conditions; a subtle, balanced pattern is not automatically a reason to reject the stone. GIA’s oval guide.
Blended centre
Pronounced bow tie
Blended centre
Heavy central shadows
Emerald and Asscher cuts have a different personality: broad, orderly reflections rather than the busy sparkle of many brilliant cuts. Choose the look you enjoy, then assess how well that individual diamond delivers it. Explore our diamond shape comparison. GIA on emerald cuts.
What about lab-grown diamonds and “Ideal” cut?
Cut matters just as much to the appearance of a lab-grown diamond, but laboratory terminology varies. IGI describes its top round-brilliant category as Excellent–Ideal. Read the full report rather than assuming “Ideal” is a universal grade above GIA Excellent. IGI’s grading process.
GIA’s current colourless-to-near-colourless lab-grown service uses an overall Premium or Standard quality assessment, introduced in October 2025. These labels combine several quality factors; they are not standalone cut grades. Older reports may use a different format. GIA’s current lab-grown service and service-change announcement.
Compare the diamond and the price together
These two Anny’s listings were checked on 19 September 2026. Both are natural, round, 1.00ct, F colour, VS2 clarity, with GIA reports listed.
| Listing | Cut | Listed measurements | Loose-stone price |
|---|---|---|---|
| F0838569C | Very Good | 6.21 × 6.25mm | A$5,943 |
| 1CD80B9A3 | Excellent | 6.28 × 6.34mm | A$6,596 |
Displayed prices include GST and cover the loose diamond only. Price and availability can change; online listings do not mean stones are held in either showroom.
These stones share the listed origin, shape, weight, colour and clarity, but differ in cut, dimensions and fluorescence. Their prices do not establish a standard cut premium or show which stone you would prefer. Both list Excellent polish and Very Good symmetry, so check those fields separately.
Start with our current natural-diamond listings or lab-grown diamond listings. Shortlist by report, compare dimensions, review video and ask about viewing arrangements before deciding.
For a typical price rather than single listings, use the calculator below. It shows what a natural and a lab-grown diamond cost by shape and carat weight, worked out each night from the diamonds available through us at one stated grade: an Excellent cut grade for natural rounds and Ideal for lab-grown rounds.
1 ct round · Natural
about A$7,538
Typical price · based on 203 diamonds available through us
Listed now, at or under this price
1 ct round · Lab-grown
about A$1,516
Typical price · based on 476 diamonds available through us
Listed now, at or under this price
At this size, lab-grown costs about 80% less than natural.
Natural: E–F colour, VS2 clarity, excellent cut for rounds. Lab-grown: E colour, VS1 clarity, ideal cut for rounds. GST included.
Put it in an engagement ringTypical prices of the diamonds available through us, updated 14 November 2026. See every shape and size in our diamond price guide.
Find the diamond that looks right to you
Anny’s can help you compare diamond options and plan a custom-made ring around your preferred stone.
Visit 92 Young Street, Frankston. Walk-ins are welcome; no appointment is required. We are open Monday–Friday, 10am–5pm, and Saturday, 10am–3pm.
Our Melbourne CBD showroom is at Level 3, 257 Collins Street, Melbourne. Email us before visiting Collins Street for engagement-ring and wedding-ring consultations. Please wait for our email confirmation before coming in. Remodelling consultations take place at our Frankston workshop. Email info@annys.com.au with your listing links, preferred shape and complete-ring budget to discuss the options or arrange a consultation.
Ask us about your diamond shortlist