Choosing your GIA diamond: shape, carat, colour, clarity
diams.com gives access to GIA-certified diamonds, in stock or to order, with their prices in CHF, EUR or USD. Shape, carat weight, colour and clarity are chosen on this page, in any order; the list of available stones appears as soon as the four criteria are set. A GIA-qualified gemmologist, in Lausanne since 2004, answers your questions before you buy.
1Shape
Understanding shape
A diamond’s shape: outline and faceting
The shape is the diamond’s outline and the arrangement of its facets. It says nothing about quality or weight: two diamonds of the same shape can differ in proportions, colour and clarity. Each shape has its qualities: the round brilliant returns the most light, elongated shapes look larger at equal weight, step cuts show off the stone’s transparency.
The nine shapes offered
- Round brilliant diamond: the most widespread shape, known for its balance and its ability to return light.
- Oval diamond: an elongated shape with a generous visual surface and a fluid elegance.
- Pear diamond: a slender silhouette, combining roundness and finesse.
- Princess diamond: a modern geometric shape with clean, assertive lines.
- Marquise diamond: an elongated, expressive shape, historically associated with classic elegance.
- Radiant diamond: a combination of straight lines and dynamic facets, with the emphasis on reflections.
- Emerald-cut diamond: a structured cut that brings out the transparency and depth of the stone.
- Cushion diamond: softened outlines giving a warm, balanced presence.
- Heart diamond: a symbolic, expressive shape that demands great cutting precision.
What the shape changes to the eye
The shape governs how light travels through the diamond, how large it appears and the balance between brightness, fire and legibility. At equal weight, two diamonds of different shapes make very distinct impressions: a 1-carat marquise looks longer than a 1-carat round brilliant, a cushion softer, an emerald cut deeper.
Choosing your shape
There is no universally ideal shape. The right choice depends on personal taste, the effect you are after and the setting you have in mind. Shape is chosen here together with carat weight, colour and clarity; each shape has its own page, with its available stones and their prices.
2Weight
Understanding weight
The carat is the diamond’s unit of weight: one carat is 0.20 gram and is divided into 100 points.
The carat, a unit of weight
The word comes from the carob seed, which served as a weight reference for the stone merchants of antiquity. Today the metric carat is exactly 0.20 gram; a 0.50-carat diamond weighs 50 points, or 0.10 gram. The GIA report states the weight to the hundredth of a carat.
The carat and how it is perceived
The carat expresses a weight, not a dimension. Two diamonds of the same weight can have different diameters depending on their proportions: a stone cut too deep looks smaller than a well-proportioned one. Shape matters too: at equal weight, an elongated shape (oval, pear, marquise) shows a larger apparent surface than a round brilliant.
Our guidelines for comparing weights
Price is not proportional to weight: it rises in steps, especially at the round figures (0.50 ct, 1.00 ct). Comparing diamonds within the same weight range, at equal shape, colour and clarity, shows what proportions and cut quality cost. The ranges offered here give direct access to the stones of each weight.
3Colour
Understanding colour
The colour of a white diamond is graded from D (colourless) to Z (visible tint) on the GIA scale; the diamonds offered here range from D to K.
The GIA colour scale, from D to Z
The GIA grades colour by comparison with master stones, with the diamond placed table down, under standardised lighting. D, E and F are colourless (exceptional white for D and E, rare white+ for F). G and H are near colourless (rare white, white): only a side-by-side comparison reveals their nuance. I and J (slightly tinted white) may show a slight tint depending on the lighting and the metal. K is slightly tinted. The further down the scale, the more perceptible a warm tint becomes.
Our view of colour
Colour is judged on the mounted stone, with the naked eye, not under the loupe. On a large diamond the tint shows more than on a small one; between two neighbouring grades, the difference is most often imperceptible once the stone is set. The metal plays a part: yellow or rose gold warms any stone, white gold and platinum reveal the nuances. Elongated shapes, marquise and pear first among them, concentrate the tint at the points.
Our guidelines for choosing colour
G and H are often the right balance between appearance and price. D to F are the choice when absolute colourlessness matters, on white gold or platinum; I to K suit yellow or rose gold, where the nuance blends into the metal. The GIA report states the grade. Colour is chosen here together with shape, carat weight and clarity; the displayed price lets you compare two neighbouring grades at equal weight.
4Clarity
Understanding clarity
Clarity describes a diamond’s inclusions and surface blemishes, graded by the GIA from Flawless to Included; the diamonds offered here range from IF to SI2.
The GIA clarity scale
Eleven grades, from Flawless (FL) to Included (I3), assigned under 10x magnification by a trained grader: FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, I3. The grade depends on the size, number, position, nature and relief of the characteristics observed. The diamonds offered here range from IF (Internally Flawless) to SI2 (Slightly Included).
Can clarity be seen?
From IF to VS2, nothing is visible to the naked eye. In SI1 and SI2, an inclusion can become perceptible depending on its position and nature, especially in step cuts, whose open table lets you see into the stone, and in large diamonds. Inclusions also tell the stone’s story: they are the signature of its natural formation, and sometimes a clue to its origin.
Our guidelines for choosing clarity
At equal weight, shape and colour, the price falls with the grade; the gap between two neighbouring grades can be significant without any visible difference. VS1 or VS2 give a stone that is clean to the eye at a measured price; SI1 can suit a round brilliant, provided you read the plot on the report; a step cut calls for a higher grade. The GIA report states the grade and, depending on its format, the position of the characteristics on a plot. Clarity is chosen here together with shape, carat weight and colour.
All four criteria must be filled in to display the available diamonds.