IT'S ALL IN THE DETAIL
The colour of diamonds is all about what you can’t see. Diamonds are valued by how closely they approach colourlessness –the less colour, the higher their value. (The exception to this is fancy colour diamonds, such as pinks and blues, which lie outside this colour range).
GIA’s colour-grading scale for diamonds is the industry standard. Many of these colour distinctions are so subtle as to be invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price. The scale begins with the letter D (colourless) and continues with increasing presence of colour to the letter Z (light yellow or brown). Each letter grade has a clearly defined range of colour appearance. Diamonds are colour-graded by comparing them to stones of known colour under controlled lighting and precise viewing conditions.
Every diamond is unique. Though some come close, only one grading of diamond is absolutely perfect under 10x magnification. Known as Flawless diamonds, these are exceptionally rare. Many jewellers have never even seen one.
Because diamonds formed deep within the earth under extreme heat and pressure, they often contain unique birthmarks. These may be either internal (inclusions) or external (blemishes). Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Using the GIA International Diamond Grading System™, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3).
The GIA Clarity Scale contains 11 grades, with most diamonds falling into the VS (very slightly included) or SI (slightly included) categories. In determining a clarity grade, the GIA system considers the size, nature, position, colour or relief, and quantity of clarity characteristics visible under 10× magnification.
Flawless (FL) - No inclusions or blemishes are visible to a skilled grader using 10× magnification. Absolutely no inclusion /imperfections (both inside the diamond crystal or on the surface).
Internally Flawless (IF) – Absolutely no internal inclusions and only extremely minimal surface blemishes or silt are visible to a skilled grader using 10× magnification.
Very, Very Slightly Included (VVS1 and VVS2) - Inclusions are difficult for a skilled grader to see under 10× magnification.
Very Slightly Included (VS1 and VS2) - Inclusions are minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification.
Slightly Included (SI1 and SI2) - Inclusions are noticeable to a skilled grader under 10x magnification and sometimes without magnification to a trained eye
Included (I1, I2, and I3) - Inclusions are obvious under 10× magnification and may affect transparency and brilliance. Visible to the naked eye.
The GIA Diamond Cut Grading System for standard round brilliants in the D-to-Z colour range is based on the assessment of seven components.
The first 3:Brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colours of the spectrum), and scintillation (the pattern of light and dark areas and the flashes of light, or sparkle, when a diamond is moved) are appearance-based aspects.
The remaining 4:weight ratio, durability, polish, and symmetry are related to a diamond's design and craftsmanship.
In GIA’s system, each component is assessed individually, taking into account the relative importance of that component in the overall cut quality of the diamond. Each cut grade, based on a relative scale from Excellent to Poor, represents a range of proportion sets and face-up appearances. There are many different proportion sets that produce attractive diamonds.
For example, look at a side view of the standard round brilliant. The major components, from top to bottom, are the crown, girdle and pavilion. A round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. It is important to note that a wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light and how attractive the diamond is to the person viewing it.
While it is important to consider many components when assessing the overall cut appearance and quality of round brilliant diamonds, an individual's preferences also play a role. Because each cut grade represents a wide range of proportion sets, individuals have the freedom to choose which particular appearance they prefer within the grade range. The diamond industry as well as the public can use cut along with colour, clarity, and carat weight to help them make more informed decisions when assessing and purchasing round brilliant diamonds.
Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip.
Just as a dollar is divided into 100 cents, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats. But two diamonds of equal weight can have very different values depending on the other members of the Four C’s: clarity, colour and cut. The majority of diamonds used in fine jewellery weigh one carat or less.
Cut v Shape
People often use the words cut and shape interchangeably. They think of cut as the shape or outline of the diamond, rather than the arrangement of facets needed to create an attractive face-up appearance. Round brilliant is the shape/cut most commonly used in diamond jewellery. Not all, but most other outlines are known as fancy shapes. Examples of traditional fancy shapes include the Pear, Oval and Marquise. Hearts, Trilliant and a variety of others are also gaining popularity in diamond jewellery.