Diamond Quality

DIAMOND QUALITY

Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions.
There are mathematical guidelines for the angles and length ratios at which the diamond is supposed to be cut in order to reflect the maximum amount of light. Round brilliant diamonds, the most common, are guided by these specific guidelines, though fancy cut stones are not able to be as accurately guided by mathematical specifics.
The culet is the tiny point or facet at the bottom of the diamond. This should be a negligible diameter, otherwise light leaks out of the bottom. The modern round brilliant has 57 facets (polished faces), counting 33 on the crown (the top half), and 24 on the pavilion (the lower half).
The girdle is the thin middle part. The function of the crown is to refract light into various colors and the pavilion's function to reflect light back through the top of the diamond.

The finest quality as per colour grading is totally colourless, which is graded as "D" colour diamond across the globe, meaning it is absolutely free from any colour. The next grade has a very slight trace of colour, which can be observed by any expert diamond value/grading laboratory.
However when studded in jewellery these very light coloured diamonds do not show any colour or it is not possible to make out colour shades. These are graded as E colour or F colour diamonds.
Diamonds which show very little traces of colour are graded as G or H colour diamonds. Slightly coloured diamonds are graded as I or J or K colour. A diamond can be found in any colour in addition to colourless.
Some of the coloured diamonds, such as pink, are very rare. A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or colour.

The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. Diamonds become increasingly rare when considering higher clarity grading. Only about 20% of all diamonds mined have a clarity rating high enough for the diamond to be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use.
Of that top 20%, a significant portion contains one or more visible inclusions. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry.
The culet is the tiny point or facet at the bottom of the diamond. This should be a negligible diameter, otherwise light leaks out of the bottom. The modern round brilliant has 57 facets (polished faces), counting 33 on the crown (the top half), and 24 on the pavilion (the lower half).
Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. When set in jewelry, it may also be possible to hide certain inclusion behind mounting hardware such as prongs in a way that renders the defect invisible. However, large clouds can affect a diamond's ability to transmit and scatter light.
Large cracks close to or breaking the surface may increase the likelihood of a fracture. Diamonds are graded by the major societies on a scale ranging from flawless to imperfect.

The carat weight measures the mass of a diamond. One carat is defined as 200 milligrams. The point unit - equal to one one-hundredth of a carat (0.01 carat, or 2 mg)- is commonly used for diamonds of less than one carat.
All else being equal, the price per carat increases with carat weight, since larger diamonds are both rarer and more desirable for use as gemstones. The price per carat does not increase linearly with increasing size.
Instead, there are sharp jumps around milestone carat weights, as demand is much higher for diamonds weighing just more than a milestone than for those weighing just less. As an example, a 0.99 carat diamond may have a significantly lower price per carat than a comparable 1.01 carat diamond, because of differences in demand.