Diamond Glossary

The knowledge and more information you have the better diamond purchase you will make. Here are a number of diamond terms that are used by jewelers to describe diamonds and which appear on diamond grading reports.

C:

Carat:
The unit of weight by which a diamond is measured. One carat equals 200 milligrams, or 0.2 grams. The word comes from the carob bean, whose consistent weight was used in times past to measure gemstones.

Carbon Spots:
An inaccurate term used by some people in the jewelry industry to describe the appearance of certain inclusions in a diamond. The term refers to included crystals that have a dark appearance, rather than a white or transparent appearance, when viewed under a microscope. In most cases, these dark inclusions are not visible to the naked eye, and do not affect the brilliance of the diamond.

Cleavage:
The propensity of crystalline minerals, such as diamond, to split in one or more directions either along or parallel to certain planes, when struck by a blow. Cleavage is one of the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process (sawing is the other method).

Clouds:
A grouping of a number of extremely tiny inclusions that are too small to be distinguishable from one another, even under magnification. The result is that, under a microscope, this grouping often looks like a soft transparent cloud inside the diamond. Of course, clouds cannot be seen with the naked eye. Usually, this sort of inclusion does not significantly impact a diamond's clarity grade.

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, GIA and AGS use a grading system which runs from D (totally colorless) to Z (light yellow).

Crown:
The upper portion of a cut gemstone, which lies above the girdle. The crown consists of a table facet surrounded by either star and bezel facets (on round diamonds and most fancy cuts) or concentric rows of facets reaching from the table to the girdle (on emerald cuts and other step cuts).

Crown angle:
The angle at which a diamond's bezel facets (or, on emerald cuts, the row of concentric facets) intersect the girdle plane. This gentle slope of the facets that surround the table is what helps to create the dispersion, or fire, in a diamond. White light entering at the different angles in broken up into its spectral hues, creating a beautiful play of color inside the diamond. The crown angle also helps to enhance the brilliance of a diamond.

Culet:
A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Once a diamond is set in jewelry, though, the setting itself generally provides the pavilion with sufficient protection from impact or wear. Large or extremely large culets were common in diamonds cut in the early part of this century, such as the Old European or Old Mine Cut. However, such large culets are rarely seen today. Most modern shapes have either no culet at all, or a small or very small culet.

Cut:
This refers both to the proportions and finish of a polished diamond. As one of "the Four Cs" of diamond value, it is the only man-made contribution to a diamond's beauty and value.

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 blemishes/inclusions. Clarity is graded on a scale from Flawless (FL) to Imperfect (I).

Crown height:
The part of the diamond that is above the girdle.

Crown height percentage:
The crown height expressed as a percentage of the average girdle diameter.

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

Certificate:
Laminated document by a gemological institute to describe a Diamond's characteristics.

Chip:
A tiny piece missing, caused by normal wear and tear, or by cutting.

Cluster setting:
This setting surrounds a larger center stone with several smaller stones. It is designed to create a beautiful larger ring from many smaller stones. Click here to learn more about ring settings.

Color:
Diamonds are graded on a color scale established by the Gemological Institute of America (GIA). The scale ranges from D (colorless) to Z. Fancy colors refer to diamonds with hues like pink, blue, green, yellow and very rarely red. Fancy colors are not included in this color scale and are considered extremely rare. Click here to learn more about color.

Canary Diamond:
An intensely colored yellow diamond. The yellow may be very slightly greenish or slightly orangey, but it must be deep enough to be a distinct asset. Such a diamond is called a fancy.

Cape:
A broad range of diamond color grades that show a distinct yellow tint face up (except for small stones in the top part of the range). The term originally referred to the Cape of Good Hope, the popular name for the area that later became the Union of South Africa. Since the average color produced by the South African mines was distinctly more yellow than the Brazilian average, the term cape became accepted for strongly yellow-tinted stones. The best grade in the group is variously called top silver cape, top cape, light cape, fine cape or silver cape, depending on the system used by the grader. Perhaps mostly commonly, cape is used as the color grade below top cape in the river-to-light-yellow system.

Carbon:
An inclusion in a diamond that appears black to the unaided eye.

Carbon Pinpoints:
The same as carbon spots but extremely small and somewhat more likely to be opaque.

Champagne Diamond:
A greenish-yellow to yellow-green diamond of a sufficiently pronounced hue to be an asset. Such a stone is called a fancy.

Cleavage Crack:
A break parallel to a cleavage plane. It is characterized by a two-dimensional nature; intersections with facets are usually straight lines. It is generally the most damaging kind of imperfection in a diamond, since it affects durability as well as beauty.

Closed Culet:
A culet on a diamond that is too small to be resolved with the unaided eye and that can be seen only with difficulty under 10x. The term is rarely used to refer to a pavilion point or ridge with no culet.

Closed Table:
A term used by some diamond men to designate a small table diameter. However, its interpretation and use varies. It may refer to a diameter less than the American cut 53% (of the girdle diameter) or, more frequently, to a table smaller than about 60%, because so many of the stones cut today have tables well over that figure.

Cloud Texture:
A group of tiny white inclusions, composed of minute hollow spaces, or very small patches of tiny crystals or other impurities that produce a cottony or clouded appearance in a n otherwise highly transparent diamond. A cloud may be so minute that it is difficult to see under 10X, or it may be large enough to deprive the entire stone of brilliancy.

Cloudy Texture or Cloud Texture:
A group of tiny white inclusions, composed of minute hollow spaces, or very small patches of tiny crystals or other impurities that produce a cottony or clouded appearance in a n otherwise highly transparent diamond. A cloud may be so minute that it is difficult to see under 10X, or it may be large enough to deprive the entire stone of brilliancy.

Commercially Clean:
The common meaning of this term is reasonably free from inclusions. IF a diamond were without flaws or blemishes, logically, it would be called flawless or perfect. Sometimes, highly flawed stones are represented as commercially clean. The obvious misleading nature of the term has led the American Gem Society to prohibit its use by Society members. It is also prohibited by the Federal Trade Commission, unless the stone meets the Commission’s definition of the term perfect.

Critical Angle:
The largest angle measured from the normal at which light can escape from and optically dense substance, and the smallest angle to the normal at which light is totally reflected within the dense substance.

Cube:
One of the seven basic forms in the highest symmetry (hexoctahedral) class of the cubic, or isometric, crystal system. It has six square faces that make 90° angles with one another, each of which intersects one crystallographic axis and is parallel to the other two. Gem-quality cube-shaped diamond crystals are so rare as to be regarded as collector’s items.

Cubic System:
A crystallographic system, the crystals of which may be described by reference to their axes of equal length, each situated perpendicularly to the plane of the other two. Diamond belongs to this system.

Cushion Cut:
The older form of the brilliant cut, having a girdle outline approaching a square with rounded corners. Essentially an old-mine cut.

Top