Diamond Glossary

Knowledge About Diamond Glossary

A
Abrasion:

Small scratches on the surface of a diamond or colored gemstone. In a diamond, these are usually white in color and caused by contact with other diamonds.

B
Bearded Girdle:

If a diamond is rounded up too quickly in the fashioning process, the surface of the girdle will lack the smoothness and waxy luster of a finely turned girdle. Consequently, numerous minute, hairline fractures extend a short distance into the stone. A girdle with this appearance is referred to as being “bearded” or “fuzzy.”

Blemish:

A clarity characteristic that occurs on the surface of a diamond. Though some blemishes are inherent to the original rough diamond, such as an abrasion, natural, nick, or scratch. most are the result of the environment the diamond has encountered since it was unearthed.

Brilliance:

The overall strength of a diamond’s light return, an average measured in the face-up position. The brightness that seems to come from the very heart of a diamond. It is the effect that makes diamonds unique among all other gemstones. 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:

One of three styles of faceting arrangements. In this type of arrangement, all facets appear to radiate out from the center of the diamond toward its outer edges. It is called a brilliant cut because it is designed to maximize brilliance. Round diamonds, ovals, radiants, princesses, hearts, marquises, and pears all fall within this category of cut.

Bruise:

A minute imperfection that breaks the surface of a diamond

Bruted Girdle:

On a diamond , a girdle that is cut, but unpolished.

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 diamond 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.

Cavity:

A type of inclusion consisting of a large or deep opening in the diamond. It may be cause by cleavage, by a blow, or may have been “pulled out” from the surface during the polishing operation.

Chip:

A curved break on a diamond that extends from a surface edge. (b) A small rose-cut diamond or single-cut melee. (c) A cleavage piece of diamond that weighs less than one carat. (d) A small, irregularly shaped 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, use a grading system which runs from D (totally colorless) to Z (light yellow).

Crown:

The upper portion of a cut gemstone, which lies 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:

Crown Angle is 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 displayed by the diamond.

Crown Height:

Crown Height is the millimeter distance the table is above the girdle.

Crown Height Percentage:

Crown Height Percentage is the crown height expressed as a percentage of the average girdle diameter..

Crystal:

Crystal is a type of inclusion where a mineral deposit is trapped inside the 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. 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.

Cutting style:

Cutting styles are different than diamond shapes. The simplest and most common way to explain cutting style is to categorize it into the following three basic types: Step-cut, Brilliant-cut and Mixed-cut.

D
Depth:

The height of a diamond from the culet to the table. The depth is measured in millimeters.

Depth Percentage:

On a diamond grading report, you will see two different measurements of the diamond's depth-the actual depth in millimeters (under "measurements" at the of the report) and the depth percentage, which expresses how deep the diamond is in comparison to how wide it is. This depth percentage of a diamond is important to its brilliance and value, but it only tells part of the story. Where that depth lies is equally important to the diamond's beauty; specifically, the pavilion should be just deep enough to allow light to bounce around inside the diamond and be reflecting out to the eye at the proper angle.

Diamond:

A crystal made up of 99.95% pure carbon atoms arranged in an isometric, or cubic, crystal arrangement. It is this unique arrangement of the carbon atoms that makes diamond look and behave differently from other pure carbon minerals such as graphite (the soft black material used to make pencils).

Diamond Cutting:

Diamond Cutting is the method by which a rough diamond that has been mined from the earth is shaped into a finished, faceted stone.

Diamond Gauge:

Diamond Gauge is an instrument that is used to measure a diamond’s length, width and depth in millimeters.

Dispersion:

Arranged around the table facet on the crown are several smaller facets (bezel and star facets) angled downward at varying degrees. These facets, and the angles at which they are cut, have been skillfully designed to break up white light as it hits the surface, separating it into its component spectral colors (for example, red, blue and green). This effect, which appears as a play of small flashes of color across the surface of the diamond as it is tilted, is what we refer to as the diamond's dispersion (also called "fire").

E
Emerald Cut:

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

Eye-Clean:

An term used in the diamond industry to describe a diamond with no blemishes or inclusions that are visible to the naked eye (i.e. a human eye which is not aided by magnifying devices such as a loupe or a microscope).

F
Facet:

The smooth, flat faces on the surface of a diamond. They allow light to both enter a diamond and reflect off its surface at different angles, creating the wonderful play of color and light for which diamonds are famous. The table below shows all the facets on a round brilliant cut diamond. A round brilliant has 58 facets (or 57 if there is no culet). The shape, quantity, and arrangement of these facets will differ slightly among other fancy shapes.

Fancy Shape:

Any diamond shape other than round – e.g. princess cut, marquise, square, emerald, oval, heart and pear.

Feathers:

These are small fractures in a diamond. They are usually caused by the tremendous stress that the diamond suffered while it was growing underground. In some cases the feather both begins and ends within the diamond's surface and, in other cases, the feather begins inside the diamond and extends to the surface. When viewed under magnification, some feathers are transparent and others have a light white appearance to them.

Finish:

The word finish is used to describe the exterior of the diamond. If a diamond is well polished, it has a very good finish.

Fire:

Often a term used instead of “dispersion,” it is the variety and intensity of rainbow colors seen when light is reflected from a diamond.

Fluorescence:

When exposed to ultraviolet light, a diamond may exhibit a more whitish, yellowish or bluish tint, which may imply that the diamond has a property called fluorescence. The untrained eye can rarely see the effects of fluorescence. Diamond grading reports often state whether a diamond has fluorescent properties. Fluorescence is not considered a grading factor, only a characteristic of that particular diamond.

G
Girdle:

The girdle is the outermost edge of the diamond between the crown and the pavilion.The girdle is not graded, but rather it is described by its appearance at its thinnest and thickest points.

Girdle Reflection:

When a diamond has a pavilion that is too shallow or flat, the girdle is seen reflected in the table.

Girdle Thickness:

A diamond’s outermost edge is also known as the girdle. Its thickness is measured as a percentage of the diameter (e.g. thin = 1.0%, medium = 3.0%, thick = 4.0% etc…) or quoted as words (such as Thick or Thin). On a grading report, the finish of the girdle will also be stated and listed as one of the following: polished, faceted or brutted.

H
Hearts & Arrows:

Hearts & Arrows is a pattern that visible in round diamonds with exceptional symmetry when view through a hearts & arrows scope.

Heart-shape Cut:

A type of fancy diamond cut, which is cut to resemble the popular Valentine's Day shape.

I
Inclusion:

A clarity characteristic found within a diamond. Most inclusions were created when the gem first formed in the earth. A general term used to refer to any external blemish or internal inclusion or flaw on or in a fashioned diamond; e.g., a feather, carbon spot, knot, fissure, scratch, natural, etc. The term “flaw” and “imperfection” are usually used interchangeably.

L
Laser-Inscription:

Laser-Inscription is the laser etched text put on diamond girdle for identification. Usually the text is the grading laboratory initials and the certification number.

Lower-Girdle Facet:

Lower-Girdle Facet is the type of facet on the pavilion of a round brilliant just below the girdle.

Laser:

Luster is the degree to which a diamond or gemstone reflects light.

M
Marquise Cut:

A type of fancy shape diamond which is elongated with points at each end.

Melee:

A term used primarily to describe small faceted diamonds or colored gemstones of approximately .12 carat or less.

N
Naturals:

Small parts of the original rough diamond's surface which are left on the polished diamond, frequently on or near the girdle. While these are blemishes, they might also be regarded as a sign of skilled cutting; the presence of a natural reflects the cutter's ability to design a beautiful polished gem, while still retaining as much of the original crystal's weight as possible. In many cases, naturals do not affect the clarity grade. In most cases, they are undetectable to the naked eye.

Another type of natural is the Indented Natural; in this case, the portion of the original rough diamond's surface which is left on the polished diamond dips slightly inward, creating an indentation. Usually, the cutter makes an effort to cut the polished diamond so that the indented natural will be confined to either the girdle or the pavilion (making it undetectable to the naked eye in the face-up position).

O
Off-Center Culet:

A culet that, due to differences in the angles of the opposite pavilion facets, is off center with respect to the girdle outline.

Open Table:

A term that is sometimes used to refer to the table on a spread, or swindled, diamond. To some, any table diameter of 60% or more of the girdle diameter is open; to others, open means 65% or more.

Oval Cut:

A type of fancy shape diamond which is essentially an elongated version of a round cut.

P
Pavilion:

Bottom portion of the stone, under the girdle, measuring to the culet.

Pavilion Angle:

Pavilion Angle is the angle measured between the girdle and the pavilion main facets.

Pear Cut:

Pear Shape diamond or gemstone is shaped like a teardrop, rounded on one end and pointed on the other.

Point:

A unit of measurement used to describe the weight of diamonds. One point is equivalent to one- hundredth of a carat.

Princess Cut:

A type of brilliant cut fancy shape that can be either square or rectangular.

R
Radiant Cut:

A type of brilliant cut fancy shape that resembles a square or rectangle with the corners cut off. It has 70 facets.

S
Single-cut:

A very small round diamond with only 16 or 17 facets, instead of the normal 57 or 58 facets of a full cut round brilliant.

Step Cut:

The step cut has rows of facets that resemble the steps of a staircase. The emerald cut and the baguette are examples of the step cut.

Symmetry:

Refers to variations in a diamond's symmetry. The small variations can include misalignment of facets or facets that fail to point correctly to the girdle (this misalignment is completely undetectable to the naked eye). Symmetry is regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

T
Table:

The flat facet on the of the diamond. It is the largest facet on a cut diamond. The large facet that caps the crown of a faceted gemstone. In the standard round brilliant, it is octagonal in shape and is bounded by eight star facets.

Table percentage:

Table Percentage is the value which represents how the diameter of the table facet compares to the diameter of the entire diamond.

Trilliant Cut:

A type of brilliant fancy shape that is triangular.