Diamond guide
Four factors set most of a diamond's price: cut, color, clarity and carat weight. Knowing how each works helps you spend where it shows.
-
Cut
Cut is how well the stone's facets are proportioned and finished. It controls how much light returns to the eye, so it matters more for sparkle than any other factor. It is not the same as shape, which is the outline of the stone. See the shapes below.
GIA grades the cut of standard round brilliants on this five-step scale. Polish and symmetry are graded on the same scale.
Cut grade What it means Excellent Returns nearly all the light that enters. Maximum brilliance and fire. Very Good Returns most of the light. Very close to Excellent, often at a lower price. Good Returns a fair amount of light. A reasonable value choice. Fair Lets a noticeable amount of light escape out the sides or bottom. Poor Loses much of its light and looks dull. Fancy shapes do not get a GIA cut grade, so we judge them from proportions, symmetry, polish and a look at the stone. AGS, another lab, grades both round and many fancy shapes on a scale from 0 (Ideal) to 10 (Poor).
-
Color
For white diamonds, color grading measures how little color the stone has. The scale runs from D, which is colorless, to Z, which shows a light yellow or brown tint.
Grades Description D–F Colorless G–J Near colorless K–M Faint N–R Very light S–Z Light Fancy-color diamonds, such as pink or blue, are graded on a separate scale.
-
Clarity
Clarity describes the tiny internal features (inclusions) and surface marks (blemishes) in a stone, judged under 10x magnification.
Grades Description FL, IF Flawless, internally flawless VVS1, VVS2 Very, very slightly included VS1, VS2 Very slightly included SI1, SI2 Slightly included I1–I3 Included 
Many stones in the VS and SI ranges look clean to the naked eye. This is where careful inspection can save you money.
-
Carat
Carat is weight, not size. One carat is 200 milligrams and divides into 100 points, so a 0.50 ct stone is 50 points.
Price per carat jumps at round weights such as 0.50, 1.00 and 2.00. A stone just under a milestone can offer better value than one at it.
-
Grading reports
An independent lab examines the stone and issues a report listing its grades and measurements. GIA and IGI are two widely used labs. Grading standards differ between labs, so the same stone can grade differently depending on who reviewed it.
Many stones carry a laser inscription of the report number on the edge, which lets us confirm the report belongs to that stone.
-
Natural and lab-grown
Lab-grown diamonds have the same chemical makeup and crystal structure as natural ones. They are made in a lab using methods such as CVD or HPHT, and they cost considerably less.
Reputable reports state whether a stone is natural or lab-grown. Resale values and long-term price behavior differ between the two, so tell us whether you are buying to wear or to hold.
Diamond shapes
Shape is a matter of taste, but it affects price, durability and how large a stone looks.
Common shapes
-
Round brilliant
The benchmark for sparkle, and the only shape with a full GIA cut grade.
-
Princess
Square with brilliant faceting. The sharp corners need protective prongs.
-
Cushion
Square or rectangle with rounded corners and a soft, pillowy look.
-
Emerald
Rectangular step cut. Long, clean facets show clarity, so choose a clean stone.
-
Oval
Brilliant cut that looks larger per carat and flatters the finger.
-
Pear
A teardrop with one point. Check that the point lines up with the center of the round end.
-
Marquise
Long and pointed at both ends, with a lot of spread for its weight. The tips can chip.
-
Radiant
Rectangle with cropped corners and brilliant faceting. More sparkle than an emerald cut.
-
Asscher
Square step cut with large cropped corners and an octagonal outline.
-
Heart
Brilliant cut with a cleft at the top. It needs good symmetry to look balanced.
Exotic and antique shapes
-
Dutch marquise
Elongated hexagon with pointed ends, cut with brilliant or step facets. A trade name, so reports describe the shape instead.
-
Rose cut
Flat base and a domed top of triangular facets, with no table. It gives a soft glow rather than sparkle.
-
Old mine cut
Antique cushion shape with a high crown, small table and large culet.
-
Old European cut
Early round brilliant with a small table and open culet, common in older jewelry.
-
Trilliant
Triangular brilliant cut. Faceting and proportions vary by cutter.
-
Shield
Shield-shaped outline with a flat top and a pointed or curved base.
-
Kite
Four-sided outline with two long and two short sides. Uncommon as a center stone.
-
Half-moon
A semicircle, usually used as side stones beside a larger diamond.
-
Bullet
A baguette with one pointed end, mostly used as accent stones.
-
Briolette
A teardrop faceted all over with no table, usually drilled for earrings and pendants.
Exotic and antique shapes have fewer buyers, and many have no standard cut grade. Availability and pricing vary, so ask us to source one for you.
Want help applying this to your budget?
Tell us what you are looking for and we will explain the trade-offs on real stones.
Request a quote