Bezel Facet

On a round brilliant diamond, these are eight large kite-shaped facets on the crown. Also called main crown facet.

Brilliance

Brilliance describes the reflections of white light coming from the diamond in “face-up” position.
It is the effect that makes diamonds unique among all other gemstones. While other gemstones also display brilliance, none have the power to equal the extent of diamond's light-reflecting power. Brilliance is created primarily when light enters through the table, reaches the pavilion facets, and is then reflected back out through the table, where the light is most visible to your eye.

Brilliant Cut Diamond

Round diamond with 57 facets (58 if there is a facet on the culet).
In this type of cutting shape, all facets appear to radiate out from the center of the diamond toward its outer edges. It is called a brilliant cut because it designed to maximize brilliance. Round diamonds, ovals, radiants, princesses, hearts, marquises, and pears all fall within this category of cut.

Carat

The standard unit of measurement of the weight of a diamond. One carat equals 1/5 of a gram or 1/142 of an ounce.
1 carat=100 points. The word Carat comes from the carob bean, whose consistent weight was used in times past to measure gemstones.

Cavity

A type of inclusion consisting of a large or deep opening in the diamond.

Clarity

The degree to which a diamond is free from internal characteristics and blemishes. Clarity is graded on a scale from Flawless (FL) to Imperfect (I).

Clarity Enhancement

Any process used to improve the apparent clarity of a diamond. This may include filling fractures and cavities with foreign substances such as glass or resin, depending on the stone.

Cleavage

A crack in a diamond which is parallel to one of its crystallographic planes. A cleavage may be caused by inherent internal strain or by a sharp blow. The crack usually extends to the surface.

Cloud

A group of minute to very small, white inclusions which give a "cloudy" appearance.

Color Grading

A system of grading diamond colors based on their colorlessness (for white diamonds) or their spectral hue, depth of color and purity of color (for fancy color diamonds). For white diamonds, IGI uses the internationally recognized grading system which runs from D (totally colorless) to Z (light yellow).

Crown

The part of the diamond that is above the girdle. It consists of the table and the crown facets below it.

Crown Angle

The angle measured between the girdle plane and the bezel facets. Along with the table size, the crown angle helps determine the amount of dispersion (also called "fire") displayed by the diamond.

Crown Height

The part of the diamond that is above the girdle.

Crown Height Percentage

The crown height measured perpendicular to the girdle and expressed as a percentage of the average girdle diameter.

Crystal

A type of inclusion. A crystal is a mineral deposit trapped inside the diamond.

Culet

The point at the bottom of a full-cut diamond. Some diamonds have a faceted culet.

Cushion Cut

An antique style of cut that looks like a mix between an Old Mine Cut (please see Mine Cut) and a modern oval cut.

Cut

The cut (or make) of a diamond refers both to the proportions and the finish of a polished diamond. The cut is the most important of the 4Cs (cut, color, clarity, carat) in determining the diamond’s overall beauty, and is the only man-made contribution to a diamond's beauty and value.

Depth

The distance between the table facet and the culet measured in millimeters.

Depth Percentage

Also called "total depth", this figure is expressed in % and is the result of the following calculation:

• Round-shaped diamond: the diamond’s depth (mm) divided by its average diameter (mm).
• Fancy-shaped diamond: the diamond’s depth (mm) divided by its width (mm).

Durability

This covers thin girdles as well as inclusions that weaken a gem.

Emerald Cut

A square or rectangular-shaped diamond with cut corners. On the crown, there are three parallel rows of facets arranged around the table and, on the pavilion, there are three parallel rows arranged around the culet. This type of cut is also known as a Step Cut because its broad, flat planes resemble stair steps.
Inclusions that are visible through the table to the unaided eye.

Eye-Clean

A term used in clarity-grading: "eye-clean" diamonds should have no inclusions that are visible through the table to the unaided eye.

Facet

The polished planes on the surface of a gemstone.

Fancy Color

Diamonds having color more intense than "Z", as well as diamonds exhibiting color other than yellow or brown are considered fancy colored diamonds. These diamonds are graded using separate systems which indicate the characteristics of the color, and not just its presence.

Fancy Shape

Any diamond shape other than round.

Feather

A fracture or break in a diamond that looks like a white feather.

Fluorescence

The property in approximately 50% of all diamonds that makes them glow when exposed to ultraviolet light (such as the lighting frequently seen in night clubs). Diamonds can fluoresce in a number of colors, but blue fluorescence is most common. Depending on its intensity, blue fluorescence may enhance the color of some diamonds by hiding their yellow tint.

Fracture

A chip or break on a diamond that is not in the direction of a cleavage plane

Fracture Filling

A treatment whereby feathers in a diamond are filled with an artificial substance. This treatment is not permanent since the filler can dissolve and escape over time.

Girdle

The outer edge, or outline, of the diamond's shape. This is the area where the average diameter, width and length of stones are measured. The girdle is situated in-between the pavilion (lower part) and the crown (upper part). It can be faceted, polished or unpolished in which case it looks granular.

Girdle Thickness

The measurement describing the girdle thickness is the average distance between the pavilion (lower part) and crown (upper part), measured in millimeters but usually expressed in percentage of the average diameter.

Pave

A style of jewelry setting in which numerous small diamonds are mounted close together to create a glistening diamond crust that covers the whole piece of jewelry and obscures the metal under it.

Hearts & Arrows (Pattern)

"Hearts & Arrows" are usually (but not necessarily) Excellent-Ideal cuts of superior quality. Polishers used "secret recipes" to create the pattern of "Hearts" looking down through the pavilion and "Arrows" seen in the table-up position. The precision and sharpness of the patterns relied on precise angles in combination with specific facet length, width and azimuth.

Ideal Cut

A diamond polished to the highest standards in precision and perfection, resulting in ideal balance between brilliance and 'fire'. The combination of angles and proportions, as well as the highest quality of polish and symmetry ensure optimal return of light.

IGI

International Gemological Institute was established in Antwerp, Belgium in 1975, and is one of a very small number of internationally recognized laboratories issuing diamond grading reports, colored stones reports, as well as fine jewelry reports. IGI also runs gemological training courses and operates a well-known and respected research department.

Inclusion

A naturally occurring imperfection in a diamond, commonly referred to as "internal characteristic". Some examples are: feathers, crystals, needles, clouds and pinpoints.

Karat

Karat is the measure of purity of gold; 24-karat being pure gold. Jewelry is usually made from 18K and 14K gold, which contain other metals for strength.

Laser Drilling

A diamond enhancement technique whereby a laser is used to drill to a dark inclusion which is then bleached in order to enhance the inclusion’s appearance.

Laser Drill Hole

A tiny tube created during the laser drilling process of a diamond.

Laser Inscription

Is the laser-etched text put on the girdle of a diamond for identification purposes. Usually the text is the laboratory initials (IGI) and the grading report number.

Length-To-Width Ratio

A comparison of how much longer a diamond is than it is wide. It is used to analyze the outline of fancy shapes only; it is never applied to round diamonds. There's really no such thing as an 'ideal' ratio; it's simply a matter of personal preferences. For example, some people prefer the look of a long, slender marquise and others prefer the look of a shorter, fatter marquise. And while many people like square princess cuts and radiants, there are some people who enjoy more rectangular proportions for these types of fancy shapes.

Loupe

A 10x magnifying lens used to examine diamonds and other gemstones.

Lower-Girdle Facet

Also called "lower halves", they are the facets on the pavilion of a round brilliant just below the girdle.

Luster

The degree to which a diamond or gemstone reflects light.

Marquise Cut

An elongated shape with pointed ends inspired by the fascinating smile of the Marquise de Pompadour and commissioned by the Sun King, France's Louis XIV, who wanted a diamond to match it.

Mine Cut Diamond

An ancient form of the brilliant diamond with a cushion-shaped outline, high crown, small table, deep pavilion, and an extremely large faceted culet.

Mohs Scale

The 10-point scale of mineral hardness created in 1812 by the German mineralogist Friedrich Mohs. It is one of several definitions of hardness in materials science. Diamond scores 10 on the Mohs Scale, 9 for Corundum (Ruby and Sapphire), 7.5 to 8 for Beryl (emerald and aquamarine) and 7 for Quartz.
Diamond is the hardest of all known natural substances.

Natural

A small rough diamond portion that can be found on some polished diamonds. This is often done so the polisher can maximize weight yield of a diamond.

Old European Cut Diamond

The earliest known form of brilliant cut diamond with a very small table and steep crown.

Optical Property

A gem's intrinsic ability to interact with light. Some optical properties are color, dispersion and fluorescence.

Pavilion

The lower part of a polished diamond, usually cone-shaped.

Pavilion Angle

The angle measured between the girdle and the pavilion main facet.

Pavilion Main Facet

The eight facets found on the pavilion of a round brilliant diamond. They run from the girdle to the culet.

Pear

Combining the best of the oval and the marquise, it is shaped like a sparkling teardrop.

Pinpoint

Internal characteristic: minute to very small, usually a whitish dot inside a diamond.

Points

1/100th of a carat. For example, a 3/4 carat diamond weighs 75 points.

Polish

The way polishers finish the smoothness of facets on a diamond. Polish is graded starting at "Excellent" and followed by "Very Good", "Good", "Fair" and "Poor".

Princess

This is a square or rectangular cut with numerous sparkling facets.

Radiant

This square or rectangular cut combines the elegance of the emerald cut's shape with the brilliance of the round cut's faceting style.

Scintillation

The small areas of light in a polished diamond that flash on and off as the diamond, observer or lighting moves.

Shape

The shape of a gemstone. The most famous are known as round, marquise, pear, oval, heart, princess, radiant, emerald, cushion and triangle but there are also many other shapes.

Star Facet

One of the eight triangular facets found at the edge of the table facet and pointing to the outline of a brilliant-cut diamond.

Step Cut

Please see Emerald Cut.

Symmetry

Symmetry of individual facets, and symmetry of the parts of the stone as well as their overall alignment, is what a gemologist must observe and grade from "Excellent" to "Poor".

Table

The largest facet, situated on top of the crown of a diamond. This is where most of the light enters and exits a diamond.

Table Percentage

The width of the table divided by the average diameter.

Upper-Girdle Facet

Also called "upper halves", they are the 16 facets found on the crown, between the girdle and the star facets.