Jewelry Education

A

AGS

Acronym for American Gem Society, a highly respected independent gemological laboratory founded in 1934, whose expert gemologists grade diamond quality and provide a Grading Report along with each stone they grade. The American Gem Society has its own rating scale for a diamond's cut.

AGS Cut Grading Scale

0	Ideal
1	Excellent
2	Very Good
3, 4	Good
5, 6, 7	Fair
8, 9, 10	Poor

Appraisal

An appraisal is a written estimate of the approximate retail replacement value of diamond jewelry, which may be used for insurance coverage or other purposes. It is not the same as a grading report, which evaluates a diamond's characteristics (such as cut, clarity, carat, symmetry, etc.). Grading reports do not provide any suggestion of monetary value, only quality.

B

Bar Setting

Bar setting is a form of a channel setting. Used in circular bands, a bar setting uses a thin bar of metal to hold the stones in place on either side, so that each bar has a stone on either side of it. See also prong setting, bezel setting, channel setting, invisible setting, pavé setting, cluster setting, and tension setting.

Bearding

Bearding is the term given to the very small feathers (small fractures that touch the diamond's surface) along the edge of a diamond, usually appearing at the girdle, or diameter of the diamond. It is usually noted as a minor comment; only severe bearding affects a clarity grading of a diamond.

Bezel Facet

This is the name given to the facet located on the crown, or top portion of a diamond. Jewelers call this the "kite" facet, because of its shape.

Bezel Setting

A bezel setting holds a diamond in place using a thin band of metal that surrounds the diamond at its middle, or girdle. It can completely or partially surround the stone, depending on the style and look desired. This type of setting provides good protection for the middle and bottom (pavilion) portions of the diamond. See also prong setting, bar setting, channel setting, invisible setting, pavé setting, cluster setting, and tension setting.

Brilliance

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

A type of round cut in diamonds, giving the stone 57 or 58 facets that are mathematically devised to produce the greatest brilliance. "Cut" here really refers more to the diamonds shape, than its proportions. Click for more on a diamond's cut.

C

Carat or Carat Weight

The standard unit of weight used for gemstones. One carat equals .200 grams (or 200 milligrams). Usually abbreviated ct.

Certificate (also known as Grading Report)

Many diamonds are certified by an independent laboratory so purchasers can feel confident that their diamond is indeed of the quality the seller represents. The way that diamonds are certified is by having them evaluated by an independent gemological laboratory with skilled gemologists who use specialized equipment to measure and evaluate each diamond's particular characteristics and attributes. This information is provided in written form and is called a diamond grading report or diamond quality document (it is sometimes referred to as a certificate, which is less accurate).

Channel Setting

In channel setting, two strips of metal hold the stone(s) in place at the sides. There is no metal between the stones. This type of setting protects the girdle area of the diamond, as well as securing small stones more effectively than a prong setting. Channel-set diamonds also sit flush with the mounting, making them less likely to get snagged on other objects, such as hair or clothing. See also prong setting, bar setting, bezel setting, invisible setting, pavé setting, cluster setting, and tension setting.

Clarity

A gemstone's relative freedom from inclusions and blemishes. Sometimes called purity; in Europe, quality. Clarity affects the value of a stone if it is visible with the unaided eye.

Cleavage

How a gemstone breaks or splits is determined by its internal atomic structure and the relative strength of the bonds between its atoms.

Cloud

Clouds are a type of inclusion found in some diamonds. They are usually small specks or hazy areas that give the diamond a milky appearance. Clouds are usually indicated on diamond grading reports. The location and size of the clouds may have a direct bearing on the diamond's value. See also feather, crystal.

Cluster Setting

When several stones are mounted together in a group, for a cluster effect. It is frequently seen with several small stones surrounding a central, larger stone. See also prong setting, bar setting, bezel setting, channel setting, invisible setting, pavé setting, and tension setting.

Color

The most important thing to know about color is, in general, the less of it a diamond has, the more valuable it is, all other factors being equal. The ideal color for a diamond is colorless, although this is extremely rare.

Crown

The crown is the top section of a diamond, above its widest point, or girdle, that comprises the table, and the star-, bezel-and upper-girdle facets.

Crown Angle

The crown angle of a diamond is a measurement of the angle, in degrees, that is formed by the facets of the upper portion, or crown of the stone. The distance from the girdle (widest point) to the table (the flat facet at the top of the stone) determines whether the crown will be thick, thin or proportionally ideal. Therefore, the higher the crown, the steeper the crown angle will be; the thinner the crown, the shallower the crown angle will be. The angles at which the crown and pavilion facets (those facets below the girdle) are cut directly affects the diamonds ability to refract light rays, which is what gives a diamond its remarkable fire and brilliance.

Crystal

A crystal is a type of inclusion found in some diamonds. It is simply a mineral deposit that has been trapped inside the diamond. Crystals are usually indicated on diamond grading reports. The location and size of the crystal may have a direct bearing on the diamond's value. See also feather, cloud.

Culet

The point on the bottom of a diamond's pavilion is called its culet. On some diamonds, the culet is actually formed into a facet; in others, it is formed into a point. Round diamonds can therefore have either 58 or 57 facets, depending on whether the culet has been faceted or not.

Cut

Cut refers to the geometric proportions to which a diamond is crafted (usually by a master diamond cutter with many years of experience). Once the diamond's shape has been determined, facets are cut. It is these facets that refract light like a prism and produce the stone's fire and brilliance. See also "Ideal Cut".

D

Depth

A diamond's depth is the distance from the Table (top) to its Culet (bottom).

Depth Percentage

Depth percentage is the measurement of a diamond's depth, relative to its diameter. A diamond's depth is measured from its table (top) to its culet (bottom). Its width is measured at its widest point (diameter), called its girdle. This depth-to-width relationship is largely responsible for the diamond's being properly proportioned, resulting in the proper refraction of light and maximum fire and brilliance. Depth percentage is often indicated on diamond grading reports. Since a well-cut diamond should have even brilliance throughout the stone, its depth percentage is probably the best indicator of a diamond's cut. If the stone has a dark center, then the depth of the diamond's pavilion is probably too great, letting light escape out the sides of the stone, instead of out the top (sometimes called a "nailhead" by the jewelry trade). If it has a ring-like shadow when viewed through the top (sometimes called a "fisheye" in the jewelry trade), the diamond's pavilion is probably too shallow. Shallow pavilions can also cause a diamond to look watery and lifeless.

Diamond

The simplest of all the gemstones, diamond consists of pure crystallized carbon. A diamond begins to crystallize far beneath the earth's surface among a mixture of liquids, gases, and crystals. They are typically found in two type of deposits: in Kimberlite pipes (which are the remnants of extinct volcanoes) or alluvial deposits (where generally they were blown out of volcanoes long ago) then washed out toward the sea in river beds and along the coastline. Diamonds can be from 1 to 3 billion years old--more than two-thirds the age of the Earth itself. Diamond is also the hardest substance known to man. In fact, it can only be cut and polished by another diamond. Despite its hardness, however, it is not indestructible. If a diamond is struck at the right angle, it can chip or break (see also Cleavage).

Dispersion

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.

E

EGL

An acronym for European Gemological Laboratory. Established in 1974, the EGL is an independent laboratory with offices in Antwerp, New York, Los Angeles, Johannesburg, Paris, Israel and Seoul, whose trained gemologists grade diamond quality and provide a diamond grading report along with each stone they grade. The EGL does not sell diamonds, and their grading tends to be a little more liberal than GIA or AGS. Therefore, the price considered for a stone with their certificate is discounted an additional 10% less than the other labs listed.

External Reflection

A diamonds polish is a good indication of the diamond cutters skill and attention to detail. The finer the polish, the brighter and more lustrous the diamond will be. While the primary light refraction that causes a diamond's fire and brilliance occurs inside its facets (called internal refraction), some of the light rays are reflected back to the viewer's eye from the surface of the stone itself. This is known as external reflection. Finely polished diamonds should display a high degree of external reflection.

Eye-Clean

Eye-clean is an expression that jewelers use to designate a gem whose flaws or inclusions cannot be detected without a loupe.

F

Facet

Facets are the flat planes or surfaces on a diamond. Each facet must be cut in exact geometric relation to the others to create the most fire and brilliance.

Fancy Colored Diamonds

Any naturally colored diamond with a noticeable depth of bodycolor 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 fancy color grading system, fancy color grades are described as faint, very light, light, fancy light, fancy, fancy intense, and fancy dark.

Fancy Shapes

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.

Feather

A feather is a type of inclusion that occurs naturally in diamonds. Feathers are simply small fractures, shaped like a bird's feather, that touch the stone's surface. They are indicated on a diamond grading report that is provided with many diamonds.

Finish

The quality of a diamonds polish, the condition of its girdle, and the precision of the cut.

Fluorescence

A characteristic in some diamonds that can affect a its value is known as fluorescence. When exposed to ultraviolet light, small percentages of diamonds fluoresce, or emit light. Fluorescence does not necessarily affect a diamond's value, however it is listed on a diamond grading report. Grades can be None, Faint, Slight, Medium, Strong or Extreme. Some reports also list the color of the fluorescence (e.g. blue, yellow, white, etc.). Fluorescence is not considered a detriment to the value of a diamond if it is in the inert (none) or faint range, however, it directly affects it's value if in the medium to strong ranges and can cause the diamond to appear "hazy" in daylight!

G

GIA

An acronym for Gemological Institute of America. Established in 1931 as the nonprofit educational resource for the gem and jewelry industry, the GIA is the universally accepted authority on diamonds. The GIA's Gem Trade Laboratory is an independent lab whose trained gemologists grade diamond quality and provide a diamond grading report along with each stone.

Girdle

The girdle is the outermost edge (diameter) of a diamond that sits in the setting, separating the upper and lower sections of the stone. It can vary in thickness, depending on how it was faceted by a cutter during manufacturing.

Girdle Thickness

A diamond's girdle, or outermost edge (diameter) that separates the upper and lower sections of the stone, can vary in thickness depending on how it was faceted by a cutter during manufacturing. Ideally, the girdle should not be too thin, or the stone may chip. If it is too thick, its brilliance may be reduced. If the girdle appears to be a wide band around the diamond, it's probably too thick, also. If you can hardly see it, its probably too thin. A properly cut girdle should be even all the way around.

Grading Report (also called a Certificate)

Many diamonds are certified by an independent laboratory, so purchasers can feel confident that their diamond is the quality the seller represents. The way that diamonds are certified is by having them evaluated by an independent gemological laboratory with skilled gemologists who use specialized equipment to measure and evaluate each diamonds particular characteristics and attributes. This information is provided in written form and is called a diamond grading report or diamond quality document (it is sometimes referred to as a certificate, which is less accurate).

The diamond's value is determined primarily by its Cut, Clarity, Color and Carat weight, which are the criteria that will be listed on most reports

H

Hardness

Hardness can be defined as resistance to scratching or abrasion, and depends upon the cohesion or force of attraction between atoms in it's crystalline structure. Diamond is the hardest of all gemstones with a hardness of 10 on the Moh's scale.

I

Ideal Cut

An "ideal cut" is a specific set of guidelines that delineate the proportions that give a diamond the highest amount of fire and brilliance. The concept of an "ideal cut" diamond originated with a diamond cutter and mathematician named Marcel Tolkowsky, in his dissertation on the subject in 1919. Sometimes called the "Father of the American Brilliant Cut", Tolkowsky was the first person to show that a diamond with 58 facets that was cut to specific proportions would result in the highest possible fire and brilliance.

Although the proportions of an ideal cut vary depending on which source you talk to (from jeweler to jeweler, country to country), there are certain ranges that are generally accepted as capable of evoking the most desirable fire and brilliance from a stone. These ranges must cause the light entering the diamond to be reflected and dispersed through the table (top), not through the sides or bottom. The ideal cut diamond possesses good symmetry, i.e. its table and girdle are parallel to each other and the culet and table are well centered. The facets are also well aligned and symmetrical. Of course, ideal cut diamonds must have excellent polish (and therefore high luster).

But most of all, an ideal cut diamond must be cut to bring out the stone's brilliance and fire, not retain the most weight from the rough cut stone. It should not have a crown or pavilion that is too shallow or excessively deep. The girdle should not be too thin, or the stone may chip. If it is too thick, its brilliance may be reduced. If the girdle appears to be a wide band around the diamond, it's probably also too thick. If you can hardly see it, it's probably too thin. A properly cut girdle should be even all the way around

Inclusion

An identifying characteristic that occurs naturally in diamonds. The fewer inclusions, the more rare the diamond and the greater its value, all other factors being equal. A truly flawless diamond is extremely rare.

Invisible Setting

Invisible-set diamonds are placed very closely together, with the metal concealed underneath the diamonds, giving them the appearance of a continuous, uninterrupted surface. Since the metal of the setting is not seen, this type of setting is an excellent way to showcase the brilliance of the gemstones (usually diamonds, rubies, sapphires, or green tsavorite garnets) themselves. The style is labor-intensive and it allows an increased amount of light to enter the stone (and, thus give off more brilliance), since there are no prongs or bezels impeding the light's entry. See also prong setting, bar setting, bezel setting, channel setting, cluster setting, pavé setting, and tension setting.

J

K

L

Length-to-Width Ratio

In stones with shapes other than round (such as marquise, pear, hearts, etc.), the length-to-width ratio is the relationship between the length of its shorter and longer dimensions.

Loupe

A loupe is a small magnifying glass used to view gemstones. Usually 10x, or ten-power, magnification. The FTC requires all diamond grading be done under 10-power magnification; any flaws not detected under this magnification are considered to be non-existent.

M

Mohs Scale

The Mohs scale is a table of relative hardness that ranks a mineral's strength and durability on a scale from 1 to 10, with 1 being talc and 10 being diamond. Developed over 100 years ago by Frederic Mohs, it is the standard scale of hardness in both mineralogy and gemology. Please bear in mind that diamond is 120 times harder than the next closest stone, corundum!

Mounting (and Setting)

The mounting is the actual ring that holds the gemstones and comes in a variety of shapes, styles, metals that offer many ways to set the actual gemstone. It is usually made of gold or platinum. The setting is the part of a ring that holds the gemstone(s) in place. For a more descriptive discussion of setting styles also see prong setting, bar setting, bezel setting, channel setting, cluster setting, invisible setting, pavé setting, and tension setting.

N

O

Optical Properties

Those characteristics of a gemstone which govern its interaction with light.

P

Pavé Setting

A setting technique for small diamonds in which the stones are set so closely together that no or very little metal shows. Pavé is French for paved, like a cobblestone road. In pavé setting, diamonds are fit into small holes and set almost level with the surface of the ring. See also prong setting, bar setting, bezel setting, channel setting, cluster setting, invisible setting, and tension setting.

Point

A point is the unit of weight equal to one one-hundredth of a metric carat (0.01 ct).

Prong

A prong is one of several claw-like wires that are bent over a diamond to hold a it in place in a mounting.

Prong Setting

In a prong setting, the diamond is held in place by a number of metal prongs, which rise above the main body of the ring and are bent over the stone to hold it in place. The number of prongs varies according to the stone's shape, as does their height above the main body of the ring. See also bar setting, bezel setting, channel setting, cluster setting, invisible setting, pave setting, and tension setting.

Polish

A diamond's polish is a good indication of the diamond cutter's skill and attention to detail. The finer the polish, the brighter and more lustrous the diamond will be. While the primary light refraction that causes a diamond's fire and brilliance occurs inside its facets (called internal refraction), some of the light rays are reflected back to the viewer's eye from the surface of the stone itself. This is known as external reflection. Finely polished diamonds should display a high degree of external reflection.

On diamond certificates issued in diamond grading reports, the diamonds are also rated on the quality of the finishing touches (see also symmetry) as excellent, very good, good, fair, and poor.

When choosing a diamond, look for Excellent, Very Good or Good ratings on the grading report.

Proportions

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.

Pavilion

The pavilion of a diamond is the lower part (below the girdle, or diameter) that comprises the Lower Girdle Facet, Pavilion Main Facet and Culet.

Q

R

Refraction

The degree to which a light beam is bent upon entering another transparent medium, such as a diamond or gemstone. The ratio of the velocity of a light beam in the air, compared to once it enters the new substance, is known as the refractive index of the gemstone. This refractive index distinguishes one species of gemstone from another.

S

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.

Setting (or Mounting)

The setting is the actual part of the mounting that holds the gemstone(s).

Shape

Diamonds are available in several shapes: round (also called brilliant or full-cut), marquise, pear, oval, princess, heart, pear, cushion, radiant, asscher, and emerald. Which shape you choose is purely a matter of personal preference. Don't confuse a diamond's shape with its Cut, which is an evaluation of the diamond's proportions and one of the main characteristics.

Of course, the most popular and commonly seen shape for diamonds is the round or brilliant cut, which has 57 or 58 facets (depending on whether the culet , or point at the bottom of the stone, is faceted or not). It's the "classic" shape that most people think of when they think of a diamond. Over time and with the advent of modern cutting technique, it became clear that it was not cost-effective to cut each and every diamond to these stringent requirements, since it resulted in lost diamond weight, and appears smaller to the eye than a "standard" cut of the same weight.

But the round cut is by far not your only choice. All shapes are capable of fantastic fire and brilliance. The only difference is the result of the diamond cutter's decision to cut the rough diamond into that particular shape based on the formation of the rough material as it is presented to him.

When diamonds are mined, they are not in the same shape we see in the finished product. The "roughs" are examined during a process known as marking, in which a planner decides how to get the greatest size, fewest inclusions and highest brilliance from the finished stone. Since diamonds are so rare and valuable, it is critical that there the smallest amount of material is wasted during the manufacturing process.

Sparkle

Sparkle is the broad flash of light, a reflection seen from the top surface of a gemstone, when it is moved back and forth and should not be confused with brilliance.

Symmetry

A grading term for the exactness of shape and placement of facets. Variations in symmetry include off-center culets and tables, poor facet alignment, misshapen facets, out-of-round girdles, and wavy girdles. Symmetry describes several factors: how the facet edges align each other; whether the corresponding facets from opposite sides of the diamond align with each other or not; and whether the facets from the crown, or top of the diamond are properly aligned with the corresponding ones on the bottom (pavilion).

On diamond certificates issued in diamond grading reports, the diamonds are also rated on the quality of the finishing touches (see also polish) as excellent, very good, good, fair, and poor.

When choosing a diamond, look for Excellent, Very Good or Good ratings on the grading report.

T

Table

The table is the name given to the large, flat facet on the top of a diamond.

Table Percentage

A diamond's table percentage is a measurement of its table width, relative to the width of the entire stone (at its girdle, or widest point). This relationship is critical for maximum fire and brilliance: too small or too large a table can hamper the diamond's ability to disperse light

U

V

W

X

Y

Z