Polished diamonds are marketed and priced based on four different properties – the famous 4 C’S: Carat weight; Color; Clarity, and Cut.
The unit of weight used for diamonds and gem-stones is the metric Carat (ct), equaling 0.2 grams. Because larger diamonds are less frequently found, as compared to smaller stones, their value increases exponentially with the weight (for example, a 1.00 ct diamond may be worth about four times the value of a comparable 0.50 ct stone).
Weight in diamonds under one carat is also referred to as points. A diamond that weighs 0.33 ct is often called a 33 pointer.
Diamonds occur in all colors. Most diamonds are slightly yellow, brown, or gray. The grading of color is done when comparing the diamond’s color to a colorless specimen – the ideal. Grades of color start from D – the colorless optimum – to Z, with the grades of D-E-F considered colorless; G-H-I-J are near colorless; K to M – very faint yellow; N to R – very light yellow; and S to Z – light yellow.
Diamonds also occur in fancy colors such as pink, blue, and canary yellow. These are very rare and tend to be expensive. See chart below for a breakdown of the color grades.
Rarest D E F G H I J K L M N O P Q R Common
Clarity grading measures the presence of naturally occurring features within the diamond (called inclusions) or some imperfections on its surface (called blemishes). The inclusions are not flaws – they are the unique “finger-prints” of the diamond and in most cases will not detract from its brilliance and beauty.
Very few diamonds are flawless and all others contain some inclusions and/or blemishes. These are graded according to their nature (feathers; clouds; carbon points), number, location, and if they are visible to the naked eye.
The classification of clarity start with FL – Flawless; IF – Internally Flawless; VVS 1 – 2 class is Very Very Slightly Included; while SI 1 – 2 is Slightly Included. For all of the above categories, the inclusions/blemishes are visible only under magnification – they are invisible to the naked eye. For diamonds graded as categories SI 3 and I 1-3, the inclusions are visible without magnification.
Rarest FL IF VVS1 VVS2 VS1 VS2 SI1 SI2 SI3 I1 I2 I3 Common
References: Diamond Clarity – https://beyond4cs.com/clarity/
Cut refers to the shape of the diamond, as well as to its proportions and finish. The most popular cut is the round brilliant, with its 58 facets and perfect symmetry.
Other cuts, called fancy shapes, include marquise, oval, pear-shape, emerald-cut, princess-cut, heart-shape, triangles, and radiants. In most cases, the shape of the rough diamond will dictate the final cut of the polished stone.
Proportions deal with the relationship between the size of the diamond’s various parts and their angles. Good proportions and symmetry ensure good reflection of light through the diamond and overall brilliance.