Four different factors are taken into consideration while grading diamonds to determine their quality and worth. These factors are cut, clarity, carat and colour. Using the grading system jewellers can compare different stones easily.
The colour of a diamond is graded from D to Z, where D indicated a true white diamond – a colourless diamond – and Z indicates a diamond that has yellow hues in it 鑽石4c. As the grading progresses from D through to Z these precious stones take on a yellowish tone. Diamonds that are graded up to H are categorized as white diamonds. The ones that are graded from I onwards start showing a hint of yellow in them. The colourless stones are the rarest of all which makes them the most valuable diamonds.
Diamonds are not always perfect as some of them have naturally occurring blemishes in them. These blemishes could be due to fractures or minerals or inclusions while the diamond is formed in the earth. These blemishes disrupt the way the light flows in the diamond and depending on the level and extent of blemishes in the diamond determines how it has been graded from Pure to Included (FL to I). Diamonds that are graded as pure/FL have no visible blemishes when seen under magnification whereas diamonds that are graded as included/I have blemishes that are visible even with a naked eye. The diamonds that are free of blemishes are very valuable and rare. The grades starts from Flawless and Internally Flawless – Pure, VVS1 and VVS2 – Very Very Small inclusions, VS1 and VS2 – Very small Inclusions, SI1 and SI2 – Small Inclusions, I1, I2, and I3 – Included.
Diamonds that are found in the earth are cut to ensure that the stone has maximum sparkle and brilliance. Quality cut is what makes a diamond expensive and valuable and this is the only factor that is influenced by humans. In order to cut a diamond perfectly, more than 50% of the rough diamond will have to be cut away by the craftsmen. The grades for a diamonds cut starts from Excellent – 1+ and 1, Good – 2 and 3, Average – 4, Commercial – 5 and 6, and Irregular – 6 and 7.
A carat is a unit that is used to measure the weight of all gemstones and this is one of the factors taken into consideration while assessing the quality of a diamond. Diamonds that have higher carat values have more sparkle than diamonds with lesser carat value as light has to travel through a larger distance