Diamond colour 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.)
Most diamonds found in jewellery stores run from colourless to near-colourless, with slight hints of yellow or brown. GIA’s colour-grading scale for diamonds is the industry standard. The scale begins with the letter D, representing colourless, and continues with increasing presence of colour to the letter Z, which tends to be for commercial use only. 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. 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.
Because diamonds formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, 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).
Every diamond is unique. None is absolutely perfect under 10× magnification, though some come close. Known as Flawless diamonds, these are exceptionally rare. 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.
- Internally Flawless (IF) – No inclusions and only blemishes 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 clearly visible under 10× magnification but can be characterized as minor.
- Slightly Included (SI1 and SI2) – Inclusions are noticeable to a skilled grader using 10× magnification.
- Included (I1, I2, and I3) – Inclusions are obvious under 10× magnification and may affect transparency and brilliance.
Cut is the factor that fuels a diamond’s fire, sparkle and brilliance. The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimetres in diameter. But without this precision, a diamond wouldn’t be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else. Though extremely difficult to analyse or quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colours of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved).
As a value factor, though, cut refers to a diamond’s proportions, symmetry and polish. 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. A wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light and hence its value.
As a rule we would recommend a diamond with Cut, Polish and Symmetry of Very good or Excellent.