All Diamond Education
The 4Cs
Cut
Everything a customer asks about diamond quality comes back to the 4Cs. Know these well and you can guide any customer confidently.
Cut is the most important of the 4Cs. It has nothing to do with the shape of the diamond — it refers to how well the diamond has been cut and polished to interact with light. A well-cut diamond reflects light beautifully from every angle, producing maximum brilliance, fire, and scintillation. A poorly cut diamond looks dull even if it has perfect color and clarity.
Luminari selects IGI Ideal Cut, GIA Excellent (3EX) for every diamond — the highest cut grade IGI awards. This means every stone is cut to return the maximum amount of light for the best possible sparkle.
The 4Cs
Color
Diamond color is graded on a scale from D (completely colorless) to Z (light yellow or brown). The closer to D, the rarer and more valuable the diamond. For most customers, diamonds in the D–F range appear colorless to the naked eye, while G–J appear near-colorless and still look beautiful in a setting.
Step-cut diamonds like emerald and asscher tend to show color more easily because their large, open facets act like windows — light passes through slowly and body color becomes more visible. Round brilliant diamonds hide color more effectively because their many facets constantly bounce light around, masking any warmth.
The 4Cs
Clarity
Clarity refers to the presence of internal inclusions (inside the diamond) or external blemishes (on the surface). Almost all diamonds — natural and lab-grown — have some inclusions, as they form under extreme conditions. The clarity grade tells you how visible those inclusions are.
VS1 is the sweet spot for most customers — eye-clean (no visible inclusions to the naked eye) at a much better price than FL or IF.
- FL, IF: Flawless
- VVS1, VVS2: Very very slightly included
- VS1, VS2: Very slightly included
- SI1, SI2: Slightly included
- I1, I2, I3: Included
The 4Cs
Carat
Carat refers to the weight of the diamond, not its size. One carat equals 0.2 grams. Larger carats are rarer and therefore more expensive — but two diamonds of the same carat weight can look very different in size depending on their cut and shape.
Diamond Shapes
Shape is a matter of personal style — there is no "better" shape. Each shape has its own personality. Help the customer choose by understanding their lifestyle, aesthetic preference, and which shapes suit different finger types.
The most classic and popular shape. Maximizes brilliance — designed with 58 facets specifically to reflect the most light.
Best for Classic style, maximum sparkle, all finger types
Elongated shape that makes the finger look longer and slimmer. Appears larger than a round diamond of the same carat weight. Very popular right now.
Best for Shorter fingers, those who want a larger-looking stone
Square or rectangular with rounded corners — soft and romantic. Has a vintage feel with a modern touch. Very flattering on the hand.
Best for Romantic, feminine style
Square shape with sharp corners. Very modern and geometric.
Best for Modern, minimalist style
Rectangular with step-cut facets — long, clean lines. Less sparkle than round, but has a sophisticated, elegant flash called "the hall of mirrors" effect. Requires higher clarity as inclusions are more visible.
Best for Elegant, sophisticated style, longer fingers
Round on one end, pointed on the other — like a teardrop. Flattering and elongating on the finger. Usually worn with the point facing toward the fingertip.
Best for Statement look, shorter fingers
Elongated with pointed ends on both sides. Dramatic and bold. Makes the finger look very long and slim. Requires a protective setting at the points.
Best for Bold, dramatic style, shorter fingers
Rectangular or square with cut corners, similar to emerald but with brilliant-cut facets — so it has both the shape of an emerald and the sparkle of a round.
Best for Those who want emerald shape with more sparkle
How To Measure Your Size
Learn how to measure your ring size at home with Luminari’s step-by-step guide and standard ring size chart to find your perfect fit.
If you already own a ring that fits comfortably, you can use it to determine your ring size. Place the ring on a flat surface and measure the inner diameter from one inside edge to the opposite inside edge, passing through the centre of the ring.
If you don't have an existing ring to measure, follow these simple steps using a strip of paper and a ruler.
Step 1 — Prepare the Paper
Cut a strip of paper approximately 0.5 cm wide.
Step 2 — Wrap Around Your Finger
Wrap the paper strip around the finger where you intend to wear the ring. Ensure it fits comfortably and snugly without being too tight.
Step 3 — Mark the Paper
Use a pen to mark the point where the two ends of the paper meet.
Step 4 — Measure the Length
Unwrap the paper and lay it flat. Use a ruler to measure the distance from the starting edge to the marked point. This measurement represents the circumference of your finger.
Note: All measurements should be taken in millimetres (mm).
Use the chart below to match your measurements with the corresponding ring size. If you measure an existing ring, refer to the inner diameter. For finger measurements, use the circumference to determine the appropriate size.
- Ring Size 48 — Diameter 15.3 mm
- Ring Size 49 — Diameter 15.6 mm
- Ring Size 50 — Diameter 16.0 mm
- Ring Size 51 — Diameter 16.2 mm
- Ring Size 52 — Diameter 16.5 mm
- Ring Size 53 — Diameter 16.9 mm
- Ring Size 54 — Diameter 17.2 mm
- Ring Size 55 — Diameter 17.5 mm
- Ring Size 56 — Diameter 17.8 mm
- Ring Size 57 — Diameter 18.1 mm
- Ring Size 58 — Diameter 18.5 mm
- Ring Size 59 — Diameter 18.8 mm
- Ring Size 60 — Diameter 19.1 mm