How to Grade Diamonds

Grading Diamonds: What You Need to Know

The intrinsic value of diamond jewellery primarily stems from the diamond itself. Grading diamonds is a nuanced process because even minute differences, often invisible to the naked eye, can significantly affect the price. It’s precisely why the industry relies on certified gemologists in specialized labs to accurately grade diamonds.

For those not in the gemology field, accessing a gemologist may not be immediate, but you can easily schedule a consultation with one of our experts today by calling 1-888-219-7001.

If you’re considering a diamond investment, such as an engagement ring, this straightforward guide will help you grasp the crucial aspects of diamond buying.

Starting with the 4 C’s—Carat, Cut, Clarity, and Color—we aim to enhance your understanding of diamond anatomy and grading standards:

Carat

Carat refers to the weight of a diamond, with one carat set at 0.2 grams. This term originates from the carob seeds once used for balancing scales due to their consistent weight. While carat weight suggests size, higher carat diamonds command exponential prices due to their rarity. 

Although carat measures the diamond’s weight, it can generally determine the diamond’s size. Here is a chart of “round” diamonds showing their carat and their relative size in millimeters.

As you go up in carat, the price increases exponentially because diamonds over one carat are far rarer. A two carat diamond is worth more per carat than a one carat diamond of equal grade.

What carat to purchase is all a matter of budget and personal preference.  If you would like to get a better comparison of different diamond sizes, view our Diamond Size Chart.

Cut

Contrary to common belief, ‘cut’ does not refer to a diamond’s shape but its facets’ arrangement, affecting how light is captured and reflected.  This is also termed as its “brilliance”. In combination with clarity, a extremely well cut diamond will showcase the inherent beauty of the stone where a moderately well cut diamond will limit the interplay between the stone and available light when viewing it.

Cut grades go from Ideal, Excellent, Very Good, Good, and then Fair & Poor. For a typical round brilliant cut diamond, the overall depth and table size are in a tight range that must be adhered to in order to achieve an “Ideal” rating.

Clarity

This grade evaluates the inherent imperfections in a diamond—external blemishes and internal inclusions. Under 10x magnification, grades vary from Flawless to Included, with the cleanest diamonds being the most valuable. Remember, flaws at certain clarity levels are not visible without magnification.

Blemishes are flaws you can see on the surface, like chips and scratches, and inclusions are flaws found inside the diamond, like bubbles, cracks, and mineral flecks.

The clarity grades are evaluated under 10x magnification (inclusions in grades F through VS are not visible to the naked eye).

Colour

Diamond colour grading actually assesses the lack of colour, with a spectrum from colourless (D) to light yellow (Z). The less colour a diamond exhibits, the higher its value, except in the case of rare coloured diamonds like blues and pinks. Unlike a typical white diamond, these stones are prized for their unique color.

For traditional diamonds, the more colourless the diamond, the more it will emphasize its brilliance as made evident by the diamond’s cut.