While diamonds come in many different shapes, cut has to do with proportion and the arrangement of facets. The cut of a diamond directly affects its beauty by using light to create brilliance, sparkle, and flashes of fire.

Diamond measurements

Diameter: The width of the diamond as measured through the girdle
Table: The large facet on the top of a gemstone
Crown: The top portion of a diamond extending from the girdle to the table
Girdle: The intersection of the crown and pavilion, which defines the perimeter of the diamond
Pavilion: The bottom portion of a diamond, extending from the girdle to the culet
Culet: The facet at the tip of a gemstone. The preferred culet is not visible to the naked eye and is graded “none” or “small.”
Depth: The height of a gemstone measured from the culet to the table

Diamond width and depth

The width and depth can have an affect on how light travels within the diamond and in turn, affect its brilliance. If the diamond is too shallow, light is lost out of the bottom and brilliance is lost. If the diamond is too deep, light is lost out of the side of the diamond, causing it to appear dark and dull.

Diamond polish and symmetry

Polish and symmetry are two important aspects of a diamond and are critical in diminishing or enhancing a diamond’s brilliance and sparkle. The polish grade describes the smoothness of the diamond's facets. The symmetry grade refers to alignment of the facets. For the most beautiful diamond, look for a symmetry grade of excellent, very good, or good. Diamonds with a symmetry grade of fair or poor should be avoided, as the misalignment of their facets could misdirect light reflection and diminish its brilliance. 

Color

Most diamonds are nearly colorless to the naked eye, but to the trained eye, diamonds have a slight tinge of yellow or brown. Colorless diamonds are extremely rare and very valuable. The color grading scale uses letters to represent colors, beginning with D (colorless) and ending at Z (light yellow or brown). Moving along the color grading scale, the color distinctions are very subtle, but these slight differences have a large impact on the diamond’s value.

Diamond Color Grade Table

Color Grade	Description	On Unaided Eye Inspection
D – F	Colorless	Stone looks absolutely clear and transparent, with no hint of color
G – I	Near Colorless	Stone looks clear and transparent. Color will be noticeable by experts
J-K	Faint yellow	Color slightly detectable and will be noticeable only by experts
L – N	Very Light yellow	Stone shows an increasing yellow tint, even to an untrained eye
O-S	Light yellow	Stone appears yellow, even to an untrained eye
T-Z	Yellow	Stone has a vibrant yellow color

Fancy Colored Diamonds

Although the majority of diamonds have a white color, there are also fancy natural-colored diamonds in intense shades of yellow, pink, green, brown, red, orange, and blue. These intensely colored diamonds are very rare and highly valuable. Because of their rarity, a deeply colored diamond can cost more than its colorless counterpart. Fancy colored diamonds are graded based on their hue and the intensity of the color. Laboratories can create fancy colored diamonds through a process called irradiation. In the process of irradiation, a naturally colorless diamond is heat treated to have a permanent fancy color.

Clarity

Formed deep within the earth, most diamonds have internal inclusions and external blemishes. Diamonds are graded on a clarity scale from flawless to included. Most flaws are not visible to the naked eye but can be indentified under magnification in featherlike shapes, crystals, bubbles, and dark flecks. Diamonds with higher clarity are more valuable than diamonds containing numerous inclusions. Diamonds without these clarity characteristics are very rare and expensive.

Diamond Clarity Grading Scale

Clarity Grade	Description	On Inspection through 10x magnification
F	Flawless	Clear stone, no inclusions or blemishes
IF	Internally Flawless	No inclusions and only insignificant surface blemishes
VVS1 – VVS2	Very, Very Slightly Included	Tiny inclusions, which are extremely difficult to find, even under 10x magnification
VS1 – VS2	Very Slightly Included	Minor inclusions, which are difficult to see under 10x magnification
SI1 – SI2	Slightly Included	Inclusions, which are easy to see under 10x magnification
I1–I2 – I3	Included	Inclusions are easy to see under 10x magnification and sometimes, may be visible with the unaided eye. Generally I3 grade is not used for jewelry purposes and is mostly used in industrial applications

Carat

Diamonds and gemstones are weighed using carats. Each carat is divided into 100 points. A quarter carat is considered 25 points, a half carat 50 points, and so forth. However, two diamonds of equal weight can have very different values depending on their clarity, color, and cut. Large diamonds are rarer than smaller diamonds, making them much more valuable. The price of a diamond rises exponentially with its size. Along with carat weight, high brilliance, which varies according to clarity, cut, and color grade are all very desirable in a diamond.

Shape

A diamond’s cut and shape describe the outline of the stone and the pattern of the facet arrangement.

Round	Emerald	Princess	Oval	Marquise
Pear	Radiant	Asscher	Cushion	Heart

Cut

Round Brilliant Cut

The round brilliant cut diamond is the most traditional and popular of all the diamond shapes. With fifty-eight facets, this shape is ideal for a diamond because it maximizes the stone’s brilliance and sparkle.

Emerald Cut

The emerald cut diamond is a square or rectangular shape stone with cut corners. An emerald cut, also called a step cut, has rows of facets, usually about forty-eight to fifty, which resemble a staircase. An emerald cut has a larger, more open table that highlights the clarity of the diamond. It also has fewer facets than other shapes, meaning less brilliance.

Princess Cut

The princess cut diamond is second in popularity to the round brilliant cut diamond. The princess cut is traditionally square in shape and has square corners. The ideal princess cut will have length to width ratio as close to 1.00:1.00 as possible.

Oval Cut

The oval cut diamond has fifty-six facets, which provide great brilliance and fire. A well-cut oval-shaped diamond can be almost as bright as a well-cut round brilliant diamond.

Marquise Cut

The marquise cut is a traditional shape having elongated pointed ends. The pointed ends make this shape the most fragile and the most expensive of brilliant style cuts.

Pear Cut

The pear cut diamond is often called a teardrop due to its single point and rounded end. The pear shape has fifty-six to fifty-eight facets and is popular for its uniqueness and brilliance.

Radiant Cut

The radiant cut is a rectangular or square shape with cut corners. The radiant cut has sixty-two to seventy facets and offers the elegance of the emerald shape with the brilliance of the princess shape.

Asscher Cut

The asscher cut is a modified version of the emerald cut. In 1902, Joseph Asscher and his company, the Asscher Diamond Co., developed and patented the asscher cut. The asscher cut has a squarer wide step cut with an octagonal outline.

Cushion Cut

The cushion cut diamond is also called a "pillow cut" diamond. The cushion cut ranges from square to rectangular and has rounded corners. It also has larger facets highlighting the diamond’s brilliance and clarity. 

Heart Cut

The heart-shaped diamond is similar to a pear-shaped diamond but with a cleft at the top. It typically contains fifty-nine facets. Due to the complexity of the shape, skilled cutting is necessary to maintain the diamond’s brilliance.