Gemology Glossary
Baguette shape
A rectangular-shaped diamond with rows of step-like facets. If the baguette’s two long sides taper inward, it is called a Tapered baguette.
Bar setting
Similar to the Channel setting, this type of setting is also most commonly used in anniversary and wedding bands, but can also be seen in bracelets and necklaces. It is a circular band of diamonds that holds each stone in by a long thin bar, shared between two stones. The Bar setting combines a contemporary and classic look.
Barion cut
This has a traditional step-cut crown and a modified brilliant-cut pavilion. A square barion cut diamond has 61 facets, excluding the culet.
Bearding or girdle fringes
The outermost portion of the diamond, called the girdle, can develop small cracks that resemble whiskers during the polishing process. The bearding can sometimes be removed, if not too dramatic, with slight re-polishing, and if the weight allows.
Bench Jeweler
A bench jeweler is a highly skilled craftsman who makes or repairs jewelry. Working with diamonds, colored stones, and precious metals, a bench jeweler's skill set can include stone setting, mold and model making, soldering, casting, engraving, enameling, and more.
Bezel setting
With a bezel setting, a rim holds the stone and completely surrounds the gem. Bezels can have straight edges, scalloped edges, or can be molded into any shape to accommodate the stone. The backs can be opened or closed and they are used to set earrings, necklaces, bracelets, and rings. Warmer-colored diamonds look stunning when bezel-set in yellow-gold.
Blemishes
The term blemish is used when the diamond has scratches or marks on the external area of the stone.
Brilliance
Liveliness, or sparkle in a stone when light is reflected from the surface and from the total internal reflection of light. The combination of all the white light reflections from the surface and the inside of the stone - it gives a polished diamond its brightness.
Brilliant-cut
Brilliant cuts are scientifically found to reflect the most light from within the stone, and often are considered to have the most brilliance of all cuts. A round brilliant-cut diamond has 58 facets. Other brilliant cuts include the heart, oval, marquise and pear shaped.
Carat
Refers to the measure of weight of a diamond. One carat is equivalent to 200 milligrams. One carat can also be divided into 100 “points.” A .75-carat diamond is the same as a 75-point or 3/4-carat diamond.
Certification (or Diamond Grading Reports)
There are many recognized gemological laboratories that can grade your diamond for a fee.
Channel setting
Used most frequently for wedding and anniversary bands, a channel setting will set the stones right next to each other with no metal separating them. The outer ridge of metal is then worked over the edges of the stones. This protects the girdle area of the diamonds better than a bead or prong setting and provides a smooth exterior surface.
Clarity
A diamond often has natural imperfections, commonly referred to as "nature’s fingerprints." These inclusions contribute to a diamond’s identifying characteristics. Inclusions are found within the diamond. Inclusions can be white, black, colorless, or even red or green. Most inclusions are undetectable by the human eye, and can only be seen with 10X magnification. Inclusions are ranked on a scale of perfection called clarity. The grades of clarity vary from F (Flawless) and (Internally Flawless) through to I (Included). Clarity scale I can be seen by the human eye without magnification. The position of these birthmarks can affect the value of the diamond.
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.
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.
Crown
This is the upper portion or the top of a diamond.
Culet
The bottom point of the diamond. It may be polished in some stones. Please note that sometimes the cutter may choose to make the culet a surface instead of a point.
Cushion cut
A mixed-cut diamond shaped like a square pillow.
Cut
Cut refers to the angles and proportions a skilled craftsman creates in transforming a rough diamond into a polished diamond. Based on scientific formulas, a well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the stone. This results in a display of brilliance and fire. Diamonds that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance and ultimately 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.
Deep cut
Cut refers to the angles and proportions a skilled craftsman creates in transforming a rough diamond into a finished diamond. When a diamond is cut too deep, it will lose or leak light through the side or bottom. This results in less brilliance and value.
Diamond
Mineral composed essentially of carbon crystallized at extremely high temperatures and pressures. In nature, diamonds form at 150 to 200 kilometers (93 to 124 miles) or more below the earth's surface. Diamond is the hardest of all known natural substances, and forms in the cubic, or isometric, crystal system. It ranges from colorless to a wide variety of colors. Poorly colored or heavily included single crystals are used for industrial purposes.
Diamond Grading Reports
There are many recognized gemological laboratories that can grade your diamond for a fee.
Dispersion
When light enters a diamond it reflects off the facets and the angles cut into the stone. This distribution of light is known as dispersion, or the display of the spectral colors. Sometimes called "fire," dispersion is the breaking up of white light into spectral hues and the "rainbow" colors you see when light passes through a prism. Diamonds are more dispersive than most other gems.
Emerald shape
A rectangular or square-shaped cut-cornered diamond.
Facets
These are tiny surfaces polished onto a rough diamond that give a finished diamond its shape. The way light interacts with these facets affects a diamond's brilliance and sparkle.
Fancy Colors
Any naturally colored diamond with a noticeable depth of body color considered to be rare or attractive. Red and green are the rarest fancy colors, followed by purple, violet, orange, blue, and pink. Yellow and greenish yellow diamonds are more common. While white, black, and gray are not, strictly speaking, spectral colors, they are also considered fancies. In the GIA color grading system, fancy color grades are described as faint, very light, light, fancy light, fancy, fancy intense and fancy dark.
Fancy shapes
Any diamond shape other than round – e.g. marquise, square, emerald, oval, heart and pear.
Feather
A feather is a type of inclusion or flaw within a diamond. It is described often as a small crack, fissure or gletz.
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. The quality of a diamond’s polish, the condition of its girdle, and the precision of the cut.
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.
Flat-top setting
Like the Gypsy setting, this setting has a band that is one continuous piece that gets thicker at the top. A flat-top setting grows broader at the top so that a faceted stone can be inserted into the ring at the broadest part. The stone is held in place by metal chips attached at the stone’s girdle. The Flat-top setting tends to have a more modern/contemporary look.
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.
Girdle
The girdle is the outermost edge of the diamond between the crown and the pavilion.
Graduate Gemologist
A GIA Graduate Gemologist (G.G.) has successfully completed GIA's rigorous diploma program which prepares jewelers and gemologists around the world to grade and identify the full range of diamonds and colored stones. A GIA Graduate Gemologist is most often a buyer, appraiser, and senior professional within the gem and jewelry industry.
Growth or grain lines
These can be considered internal flaws, and can often be seen only by rotating the diamond very slowly. They can appear and disappear almost instantaneously. They appear as small lines or planes within the diamond.
Gypsy setting
The Gypsy setting is predominantly used for men’s jewelry. The band is one continuous piece that gets thicker at the top. The top is dome shaped and the stone is inserted in the middle. There are no prongs; therefore the look is smooth and clean.
Illusion setting
This setting is more intricate than others in that it surrounds the stone to make it appear larger. The metal that surrounds the stone usually has an interesting design.
Inclusions
Often referred to as "nature’s fingerprints," these are internal imperfections within most diamonds. They are what makes a diamond so unique, as a fingerprint does for a person. These birthmarks are measured on a scale of perfection known as clarity. Some common names of inclusions include cloud, crystal, pinpoint, and feather. The position of inclusions can affect the clarity of a diamond and therefore the value.
Marquise shape
A boat-shaped diamond that is long and thin with gently curved sides that come to a point on either end. Marquise is part of the brilliant-cut family.
Mixed-cut
This cut has both step-cut and brilliant-cut facets. Mixed cuts combine the beauty of the emerald cut with the sparkle of the brilliant cut.
Optical Properties
Those characteristics of a gemstone which govern its interaction with light.
Pavilion
Bottom portion of the stone, under the girdle, measuring to the culet.
Pinpoint
A pinpoint is a small dot, which is an inclusion within a diamond. A gathering of pinpoints is called a "cluster" or "cloud." A cloud or cluster can appear as a hazy area in the diamond.
Polish
Indicates the care taken by the cutter in shaping and facetting the rough stone into a finished and polished diamond.
Poor cut
Cut refers to the angles and proportions a skilled craftsman creates in transforming a rough diamond into a finished diamond. A poorly cut diamond can be either cut too deep or too shallow. A deep or shallow cut diamond will lose or leak light through the side or bottom. This results in less brilliance and value.
Princess cut
A square or sometimes rectangular-shaped modified brilliant-cut diamond.
Prong or claw setting
It consists of four or six claws that cradle the diamond. Because this setting allows the maximum amount of light to enter a stone from all angles, it sometimes can make a diamond appear larger and more brilliant than its actual weight. This setting can also hold larger diamonds more securely. Your choices of variations with the prong/claw setting traditionally range from: pointed, rounded, flat and V-shaped.
Proportion
Proportion refers to the angles and relative measurements of a polished diamond. More than any other feature, proportions determine a diamond's optical properties. Studies have shown that table size, crown angle, and pavilion depth have a dramatic effect on a diamond's appearance.
Radiant cut
A rectangular or square shaped diamond with step-cut and scissor-cut on the crown and a brilliant-cut on the pavilion.
Scintillation
When light reflects from a diamond, the sparkling flashes that come from the facets of the gem are known as scintillation. Sometimes called "sparkle," scintillation refers to the tiny flashes of light when the diamond, the light source, or the observer moves. It depends on the number, size, and position of the facets. The quality of the polish affects scintillation, too.
Shallow cut
Cut refers to the angles and proportions a skilled craftsman creates in transforming a rough diamond into a finished diamond. When a diamond is cut too shallow, it will lose or leak light through the side or bottom. This results in less brilliance and value.
Shape
Shapes other than the standard round brilliant are called fancy shapes or fancy cuts. Their names are based on their shapes. The best known are the heart, marquise, pear-shaped cut, emerald-cut, oval, and radiant.
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
A diamond's symmetry is the arrangement of the facets and finished angles, created by the diamond cutter. Excellent symmetry of a well-cut and well-proportioned diamond can have a great effect on the diamond's brilliance and fire. Grading reports will often state the diamond's symmetry in terms Excellent, Very good, Good, Fair, or Poor.
Table facet
This is the largest facet of a diamond. It is located on the top of the diamond. The table facet is sometimes referred to as the “face.”
Table spread
Term used to describe the width of the table facet, often expressed as a percentage of the total width of the stone.
Tension setting
A tension-set diamond is held in place by the pressure of the band’s metal, which is designed to “squeeze” the stone. The result is a highly contemporary, fashionable look and can be used to set necklaces, earrings, and rings.
Tolkowsky, Marcel
In 1919 Marcel Tolkowsky calculated the best theoretical compromise for the cut of a diamond to release the most beauty. The width of the table facet was found to be 53% of the total width of the stone, with a pavilion angle of 40 degrees and 45 degrees. The Tolkowsky cut provides the basis for the modern American cut.
Trillion shape
Is a triangular-shaped diamond with 50 facets. Trillions are commonly used as sidestones.
Well cut
Well cut proportions ensure the maximum compromise between fire and brilliance. When light enters a properly cut diamond, it is reflected from facet to facet, and then back up through the top, exhibiting maximum brilliance, fire and sparkle.
