If possible, you should aim to buy a certified diamond with an independent grading report from a respected grading entity, such as the Gemological Institute of America (GIA). Diamond certificate issuers generally use a standardized system, evaluating a diamond’s, cut, clarity, colour and carat weight. These are known as the 4 Cs and a basic understanding of these is essential when choosing a diamond.
The cut of a diamond does not refer to its geometrical shape (round, princess, emerald, etc.) but rather to its overall symmetry, proportioning and polish of its facets. The beauty of a diamond depends more on cut than on any other factor, with a high quality cut noticeably enhancing a diamond’s brilliance (brightness), scintillation (flashes of light and dark or ‘sparkle’) and fire (flashes of colour).
Learn More About Cut Grades
The cut grades assigned by the GIA are as follows:
Excellent – Reflects nearly all of the light that enters the diamond. Excellent Cut diamonds display maximum fire and brilliance.
Very Good – Reflects most of the light entering the diamond. This cut appears similar to the Excellent Cut under normal lighting conditions.
Good – Reflects the majority of the light entering the diamond giving an above average appearance. This cut can be excellent value compared with higher grades.
Fair – Allows much of the light that enters the diamond to escape from the sides or the bottom. This can be a suitable cut for diamonds below 0.75 carat weight as the difference in sparkle is harder to perceive.
Poor – Most of the light entering the diamond is lost, giving a noticeably dull and lifeless appearance. It is generally best to avoid Poor Cut diamonds of any size.
The weight of a diamond is measured in carats or points. One carat is equal to 200 milligrams or 100 points. Diamonds of greater weight are more rare and hence the price of diamonds rises disproportionately as carat weight increases, with sharp jumps around the milestone carat weights.