There are several factors that determine the value of a diamond. When buying a diamond you might be surprised to find that two stones with exactly the same weight have totally different prices. The combination of colour, cut, clarity and carat weight determines the price.
THE 4 C`s
The weight of a diamond is expressed in carats. One carat is equal to 0.2 grams and one carat equals 100 points.
The word “carat” comes from the use of the carob seed which was used to weigh stones and precious metals. However, this was a factual inaccuracy, as their mass varies about as much as seeds of other species.
All diamonds have traces of their own growth history. In gem quality diamonds, this concerns minute internal and external characteristics, graded under Clarity.
This grade goes from FL (flawless), VVS (very very slightly included), VS (very slightly included), SI (slightly included) to I (included). Only from “I” can one see the inclusion with the naked eye.
Most diamonds range from slightly yellowish to colourless. The colour grade is determined by comparison with a series of master-stones. The best colour being colourless (D), then goes down the alphabet where up to the colour H still registers as white. By the colour S the stone is obviously yellow.
Diamonds come in a range of fancy colours like bright yellow, browns and black, blues, pink and even purple. The fancy blues and reds are very rare and extra expensive.
The fire, brilliancy and scintillation of a diamond are largely determined by the proportions of the various parts of the stone. This might even be the most important factor because without fire, even the most clean white diamond will look like a piece of glass.
It is also worth mentioning that there are other factors like fluorescence that can determine value of a diamond.
Then of course there is the 5th C which is the confidence of the buyer in the dealer; ensure that your jeweller has good ethics and provides you with a certificate.