Whether you are looking at round or emerald cut diamonds, it’s important to know the different factors at play when evaluating diamond quality. The quality of a diamond is based on a combination of factors, including clarity, color and cut.

What is the Most Common Diamond Quality Based on Shape?

For clarity (internal birthmarks and external blemishes), diamond quality scales have eleven grades ranging from “Included” (lowest quality) to “Flawless” (highest quality of diamond). Most diamonds fall into the “Very Slightly Included (VS)” category. This is where those internal inclusions are minor. Inclusions are composed of gases, solids, or liquids that were trapped in a diamond as it formed. A diamond quality rating of “Flawless” just means there are no visible inclusions or blemishes under 10-times magnification. A completely colorless diamond is the highest color grade (D). While both color and clarity are important, the cut is usually the most important factor. Flawless colorless diamonds may be rare, but how to tell the quality of a diamond lies in how its facets are cut.

A diamond quality guide can help you understand what is the best quality of diamond, whatever its shape.

Diamond Quality Chart and Price

A diamond quality chart and prices can help you compare clarity, color and cut grades within similar carat weights. The difference in value is usually due to types of inclusions or quality of cut. When it comes to diamond quality, the cut is paramount to a diamond’s beauty. In the same way that Michelangelo chipped away all the marble that wasn’t his masterpiece “David,” a diamond cutter chips away at a rough diamond until a perfectly cut diamond emerges. Well, that’s the way it’s supposed to go anyway. Oftentimes, size is favored over creating a masterpiece.

How to tell the quality of diamond involves knowing how the “Four C’s” rank within each silhouette. The only way to get the highest quality diamond for the best price is to understand these finer points.

Oval Cut Diamond

An oval cut diamond is cut to sparkle like a round cut diamond. The most famous oval cut diamond may date back to the fourteenth century, but the modern day oval didn’t hit the scene until the 1950s. Movie stars Salma Hayek and Blake Lively, and fashion model Heidi Klum, all have had oval cut diamond engagement rings.

Buying an oval diamond ring can save you money over a round cut and look larger to boot. When choosing an oval cut diamond, it’s better to spend more on cut than on color or clarity.

Best value parameters for oval cut diamonds:

Color: H
Clarity: SI1
Cut: 1.25 to 1.50 length-to-width ratio (otherwise looks round or marquise)

Princess Cut Diamond

The princess cut diamond was created in the 1980s in response to how much rough stone is lost when cutting rounds (about 60-percent). Because of the way its cut, it looks smaller than its actual carat weight. This cut is second only to round in popularity.

Best value parameters for princess cut diamonds:

Color: I
Clarity: VS2 (avoid inclusions in the table and at the diamond’s chip-prone corners)
Cut:
- length-to-width ratio: should not exceed 1.05
- diamond depth and table percentages: 65 to 75

Pear Shaped Diamond

Pear shaped diamonds date back to the fifteenth century, about the time Gutenberg was giving his printing press a twirl. Not as popular back then, this cut is now worn by celebrities and royals the world over. In the 1960s, movie siren Elizabeth Taylor wore a famous 69.42-carat pear shaped diamond and crooner Frank Sinatra proposed with a pear shaped diamond ring to movie star Mia Farrow. Today, style-icon Victoria Beckham, tennis goddess Anna Kournikova, and actress Katherine Heigl all have sported pear shaped diamond engagement rings.

Best value parameters for pear shaped diamonds:

Color: H (tips darker with larger carat weights)
Clarity: SI1 (rounded end good at hiding flaws
Cut: to find a pear shaped diamond that’s just-Goldilocks-right requires guidance, this hard to cut shape many end up too short, too long, or not properly rounded

Emerald Cut Diamond

George Clooney settled down with an offering of a 7-carat emerald cut diamond engagement ring. Jay-Z put an 18-carat emerald cut diamond flawless engagement ring on Beyonce’s finger.

One of the oldest cuts, an emerald cut diamond was born about the time Da Vinci was painting his “Mona Lisa.” This cut mimics the way emerald gemstones are cut. It enhances clarity and makes corners more stable by cropping them. This shape looks larger than other shapes at the same carat weight.

Best value parameters for emerald cut diamonds:

Clarity: VS2 (large table easily shows imperfections)
Cut:
- length-to-width ratio: 1.30 to 1.60
- diamond table and depth percentages: 59 to 70

Asscher Cut Diamond

Asscher cut diamonds are a mix of princess and emerald cuts and was the first cut to be patented (turn of twentieth century) by the Asscher family. This family has cut some of the largest and most historic diamonds.

It’s the choice of Hollywood A-listers like Gwyneth Paltrow and royals like Pippa Middleton. The most famous Asscher cut diamond in the world was a 33.19 carat stone worn by Elizabeth Taylor.

Best value parameters for Asscher cut diamonds:

Color: D-H (for larger carat weights, go more toward colorless)
Clarity: SI1 to VS2
Cut:
- length-to-width ratio: 1.04 to 1.06
- diamond table and depth percentages: 57 to 60

Cushion Cut Diamond

This square-shaped cut with rounded corners is akin to the old mine cut from the sixteenth century. This was the “it diamond” during the nineteenth century (the round brilliant of its time).

Prince Harry proposed with a cushion cut diamond engagement ring to American actress Meghan Markel. Kanye West put a 15-carat flawless cushion cut diamond ring on Kim Kardashian’s finger to seal the deal.

Best value parameters for cushion cut diamonds:

Color: D-H
Clarity: VS2
Cut:
- length-to-width ratio: 1.00 (if slightly rectangular, 1.10 to 1.20)
- diamond table and depth percentages: 58 to 60

Round Cut Diamond

The round cut diamond we know today wasn’t possible until the invention of industrial age tools. This shape allows for more eye-catching facets than any other cut. Round cut diamonds are a classic that actors Johnny Depp, Ashton Kutcher, and John Krasinski all proposed with.

It’s very important to make sure that a round cut diamond is cut neither too deep or shallow. If too shallow, light will travel out the sides of a diamond. If too deep, the bottom. This makes a diamond with every reason to shine a dull dud.

Best value parameters for round cut diamonds:

Color: J-L
Clarity: SI1