Diamonds and the four C’s
Understanding diamonds requires knowledge of the four C’s: cut, colour, clarity and carat weight. It is the interplay of these various characteristics that will determine a stone’s beauty and value.
Colour
Colour is personal: some people like a diamond with an ice-cold whiteness (colourless or near-colourless), while others prefer the golden glow of a warmer colour. Diamonds with no colour like D, E, F, are very rare and are more expensive than near-colourless (G, H, I, J) diamonds.
Diamonds with a faint tinge of color (K, L, M, N, O) have a slightly warm colour and are more affordable. For those who want a larger diamond within a certain budget, selecting diamonds with a lower colour grade may be the best option.
GIA Colour Scale:
D, E, F: colorless
G, H, I, J: near colorless
K, L, M: faint yellow or faint brown
N, O, P, Q, R: very light yellow or very light brown
S through Z: light yellow or light brown
Most diamonds appear colorless but actually have slight tones of yellow or brown. The closer the stone comes to colourless, the more valuable it is. Diamonds are graded on a colour scale ranging from D (colourless) to Z (heavily tinted.) Only a highly skilled professional will detect any color in E or F stones, and the colour in diamonds rated up to J will be virtually invisible when set in a ring or other jewellery.
Colour is only one of the four C's so even when a stone has a visible tint, such as K or lower, it can still be very lovely if it has good clarity and cut. How the diamond is set can make a difference, too; you might not want to put a truly colourless diamond in a yellow gold setting since the yellow colour will reflect in the stone. On the other hand, a slightly yellow stone will appear whiter in a yellow gold setting.
Diamonds also come in a wide variety of other colours, including red, blue, green and a bright yellow known as "canary." These are graded as Z+ and are known as "fancy" diamonds. Ones with good colour are very rare and can sell for much more per carat than white diamonds.
Clarity
Clarity refers to how free a diamond is from nature's "birthmarks," or tiny, generally microscopic imperfections that make each diamond unique.
Diamonds are assigned clarity grades based on what can be detected with ten-power magnification. Most internal features (inclusions) and external features (blemishes) in the diamond have little or no effect on brilliance and fire.
So if small clarity characteristics don't affect a diamond's beauty, why are diamonds with higher clarity grade so expensive? It's simply because diamonds with relatively few clarity characteristics are very rare. Fortunately, diamonds of all clarity grades and prices, including those with eye-visible inclusions, can look beautiful depending on how well they're cut and other factors. The best advice is to look at several diamonds of different clarity grades and let your eye be the guide!
Carat
Diamond weight is stated in carats, a measurement derived from the more romantic, (but less accurate) original scale of comparison using the seeds of the carob tree which were very uniform and consistent in weight. Precision balances are now used and a carat has been standardized as equivalent to one fifth of a gram.
One carat is divided into 100 points, so for example, a diamond weighing half a carat can also be described as weighing 50 points or 0.50 carats.
Diamonds over 1 carat are particularly rare. Less than 5% of gem quality diamonds achieve this magic weight once they are cut and polished, making them more desirable and, inevitably, more expensive.
All other things being equal, the greater the carat weight, the rarer the diamond and the more expensive it is.
Although many people equate "bigger" with "better," diamonds of all carat weight have the potential to be lively, exciting, and beautiful. The most important thing is to buy the one that's right for you.
Cut
It is the cut that makes a diamond sparkle! A well-cut diamond will reflect light to its optimum, creating brilliance and fire. Brilliance refers to the return of light to the eye through the diamond and the prism effect, the separation of white light into a rainbow of colours, is traditionally called the Fire of the stone.
Cut is not shape, ie, pear, round, oval. Cut refers to the quality of the proportioning, polish, and symmetry.
Diameter: The width of the diamond as measured through the girdle.
Table: The flat top and largest facet of a gemstone.
Crown: The top portion of a diamond extending from the girdle to the table.
Girdle: The narrow band around the widest part of a diamond.
Pavilion: The bottom portion of a diamond, extending from the girdle to the point of the stone.
Culet: The facet at the tip of a gemstone.
Depth: The height of a gemstone measured from the culet to the table.