GUIDE · DIAMONDS

The 4Cs of diamonds: cut, colour, clarity and carat

Every diamond is judged on four criteria: cut, colour, clarity and carat weight. They were created by GIA, the Gemological Institute of America, and are used today by laboratories and jewellers all over the world.

Vanni Pesciallo, a GIA-graduate gemmologist, explains them. Below you can try them out: choose a colour, a clarity grade and a weight, and see what changes.

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Cut
THE LIGHT

The cut decides how much light returns to your eyes

A diamond has no light of its own: it sparkles because of how it is cut. The facets let light in, reflect it inside and send it back upwards. If the diamond is too shallow or too deep, part of the light escapes through the bottom and the diamond looks dull.

For the round brilliant, GIA gives a cut grade from Excellent to Poor.

Try it: how light travels

Brightnessthe white light the diamond returns
Firethe flashes of spectral colour
Scintillationthe sparkles and dark areas as it moves

Rays calculated with the refractive index of diamond (2.42), in a simplified profile with exaggerated proportions. Dashed line: light that is lost.

Colour
FROM D TO Z

The whiter the diamond, the rarer it is

In 1953 GIA introduced the D-to-Z colour scale. D is colourless; towards Z the diamond takes on an increasingly visible yellow, brown or grey tint. Grades are assigned by comparing the diamond with master stones under controlled lighting.

Pink, blue or other intensely coloured diamonds fall outside this scale: they are called fancy diamonds.

Try it: choose a letter
ColourlessNear colourlessFaintVery lightLight
DColourless

Groups and names from the GIA colour chart. The tint in the drawing is exaggerated so it shows on screen.

Clarity
AT 10× MAGNIFICATION

The diamond’s fingerprints

Almost every diamond is born with small inclusions inside and marks on the surface. GIA examines it at 10× magnification and gives it one of 11 grades, from Flawless to Included.

No two diamonds have the same inclusions in the same places, which is why they also help to identify it.

Try it: choose a grade
FLIFVVSVSSII
VS1Very Slightly Included

GIA definitions. The inclusions in the drawing are enlarged and indicative.

Carat
THE WEIGHT

One carat weighs 200 milligrams

The carat measures weight, not size. One carat equals 200 milligrams and is divided into 100 points: a 0.50 carat diamond weighs 50 points.

Doubling the weight does not double what you see: the weight is spread across every dimension, and from above the diameter grows much less.

Try it: move the slider
1 carat
1.00 carat
1.00carats
100points
200milligrams

The view from above is calculated in proportion to the weight, for diamonds of the same cut. These are not measurements in millimetres.

CREATE YOUR DIAMOND

Choose the shape, weight and origin: see the diamond and its price

An estimate for the diamond alone, natural or lab-grown, in the quality we use in our atelier. When you like it, send us your request: we will reply with the real stones available and their certificates.

View from above · Brilliant1.00 ct
approx. 6.5 mm
1 · Shape
2 · Weight1.00 ct
3 · Origin
Our quality
D–FColour
FL–VVS2Clarity
ExcellentCut

Excellent polish and symmetry, no fluorescence, GIA, IGI or HRD certificate.

Natural diamond
–
Estimate, incl. VAT
Lab-grown diamond
–
Estimate, incl. VAT

“A diamond’s beauty depends on its cut more than on anything else.”GIA · GEMOLOGICAL INSTITUTE OF AMERICA

Diamond rings and bracelets

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Aura ring in 18kt rose gold with white diamond
Aura ring in 18kt yellow gold with white diamond
This product has multiple variants. The options may be chosen on the product page
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Aura

Price range: CHF 7’800 through CHF 29’000
Diamond tennis bracelet in 18k white gold – Classic Tennis, Vanni Pesciallo
Diamond tennis bracelet in 18k rose gold – Classic Tennis, Vanni Pesciallo
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Classic Tennis

Price range: CHF 2’490 through CHF 30’530
Voltige Solo, pear cut ring in 18kt white gold
Voltige Solo, pear cut ring in 18kt rose gold
This product has multiple variants. The options may be chosen on the product page
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Voltige Solo, pear cut

Price range: CHF 2’200 through CHF 7’300
Voltige Solo, round brilliant cut ring in 18kt white gold
Voltige Solo, round brilliant cut ring in 18kt rose gold
This product has multiple variants. The options may be chosen on the product page
Add to wishlist

Voltige Solo, round brilliant cut

Price range: CHF 1’790 through CHF 3’590

    THE CERTIFICATE

    The 4Cs in black and white

    Every one of our diamonds has a GIA or IGI certificate stating its cut, colour, clarity and weight, and for lab-grown diamonds its origin too.

    In the atelier we read it together and, as gemmologists, we check the diamond with our instruments before it becomes your ring.

    NATURAL OR LAB-GROWN DIAMOND

    The questions we are asked most often about the 4Cs. For prices, read our guide how much an engagement ring costs.

    THE 4Cs

    GIA, the Gemological Institute of America, founded by Robert M. Shipley. In 1953 GIA also introduced the D-to-Z colour scale.

    For beauty, the cut: according to GIA it matters more than anything else. For the price, all four count together. In the atelier we balance them with you according to your budget.

    They are clarity grades. VS means the inclusions are minor, ranging from difficult to somewhat easy to see at 10× magnification. SI means a skilled grader notices them at 10× magnification.

    200 milligrams. It is divided into 100 points: a 25-point diamond weighs a quarter of a carat.

    CERTIFICATES

    It is the document from a gemmological laboratory that states the diamond’s 4Cs. Every one of our diamonds has a GIA or IGI certificate.

    Yes: a lab-grown diamond is judged on the same criteria. The certificate also states its origin.

    Yes: we look at it together in the atelier and, as gemmologists, we check the diamond with our instruments.

    CHOOSING

    With the shape and the budget. Then, in the atelier, we choose with you the right balance of cut, colour, clarity and carat.

    Our rings are made with either, and the 4Cs are read in the same way. We explain the differences in our guide to natural or lab-grown diamonds.

    At the atelier in Balerna, Monday to Friday (Saturday on request), or at the boutique in Locarno, Wednesday to Saturday. Always by appointment.