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Blemish | Brilliance | Bar Setting | Bearding | Bezel Facet | Bezel Setting | Brilliant Cut |

Carat | Carbon Spots | Certificate | Channel Setting | Clarity | Cleavage | Clouds | Cluster Setting | Color Grading | Color | Crown | Crown Angle | Crystal | Culet | Cut |

Depth | Depth Percentage | Diamond | Diamond Cutting | Diamond Gauge | Dispersion

Emerald Cut | External Reflection | Eye-Clean

B

Blemish: a clarity characteristic that occurs on the surface of a diamond. Though some blemishes are inherent to the original rough diamond, most are the result of the environment the diamond has encountered since it was unearthed. (For more information on the most commonly occurring types of blemishes, please see our detailed discussion, Diamond Education: Clarity.)

Brilliance: the brightness that emanates from the very heart of a diamond. The brillance factor makes diamonds unique among all other gemstones. While other gemstones also display brilliance, none equals a 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.

Bar Setting: similar to a channel setting (see below). A bar setting uses a thin, circular bar of metal to hold the stones in place on either side, so that each bar has a stone on either side of it.

Bearding: 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 widest part, of the diamond.

Bezel Facet: the facet located on the crown, or top portion, of a diamond. Jewelers call this the 'kite' facet because of its shape.

Bezel Setting: holds a diamond in place using a thin band of metal that surrounds the diamond at its middle, or girdle. Bezel settings completely or partially surround the stone, depending on the style and look desired, and provide good protection for the middle and bottom (pavilion) portions of the diamond.

Brilliant Cut: a type of round cut that gives the diamond 57 or 58 facets mathematically devised to produce the greatest brilliance. 'Cut' here really refers more to the diamond's shape than its proportions.

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C

Carat: measurement of a diamond's weight. A carat is equal to 200 milligrams. (Don't confuse this Carat with the term 'Karat,' which is a measure of the purity of gold.) For accuracy, diamonds should be weighed when they are not mounted in a setting. Each Carat is divided into 100 parts called 'points,' so a 1-carat diamond has 100 points, a ¾ carat has 75 points, etc.

Carbon Spots: misnomer used by some people in the jewelry industry to describe the appearance of certain inclusions in a diamond. 'Carbon spots' are actually 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.

Certificate: a guarantee by an independent laboratory that the diamond is indeed of the quality the seller represents. Diamonds are certified by an independent gemological laboratory with skilled gemologists who use specialized equipment to measure and evaluate each diamond's particular characteristics and attributes.

Channel Setting: a setting where two strips of metal (gold, platinum, etc.) hold the diamond(s) in place at the sides. There is no metal between the stones. This type of setting protects the girdle area of the diamond and secures 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.

Clarity: measured by a jeweler's loupe (a small magnifying glass used to view gemstones) under 10-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.

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. Diamond cutters use one of two processes--cleaving or sawing--to split rough diamond crystals in preparation for the cutting process.

Clouds: a grouping of a number of extremely tiny inclusions too small to be distinguishable from one another, even under magnification. But under a microscope, this grouping often looks like a soft transparent cloud inside the diamond. Clouds cannot be seen with the naked eye, so usually do not significantly impact a diamond's clarity grade. Diamond World will not sell any diamond with clouds severe enough to affect the brilliance of the diamond.

Cluster Setting: several stones mounted together in a group, for a cluster effect. Often several small stones surround a central, larger stone.

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

Color: the most important thing to know is that, in general, the less color a diamond has, the more valuable it is, all other factors being equal. The less color a diamond has, the more purely it can refract the light that enters it, making it sparkle with brilliance and fire. Diamond colors range from colorless to slightly yellow or brown, to more rare and costly pink, green or blue stones (commonly referred to as 'fancy' diamonds). Excluding 'fancy' diamonds, the ideal color for a diamond is colorless, although this is extremely rare.

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

Crown Angle: a measurement of the angle, in degrees, 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 diamond's ability to refract light rays, which is what gives a diamond its remarkable fire and brilliance.

Crystal: 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. Be aware that the location and size of the crystal may have a direct bearing on the diamond's value.

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

Cut: the only one of the 4Cs that is within a human's control. '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. These facets refract light like a prism and produce the stone's fire and brilliance.

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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, there re two different measurements of the diamond's depth:
1) the actual depth in millimeters (under 'measurements' at the top of the report);
2) 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 reflect out to the eye at the proper angle. Keep in mind, also, that correct depth percentages vary based on the diamond's cut. For example, a 75% or 78% depth in a princess cut diamond would be typical and quite attractive. However, a depth of even 65% would be unnecessary and even detrimental to a round diamond's beauty.

Diamond: pure crystallized carbon, the simplest of all the gemstones. A diamond begins to crystallize far beneath the earth's surface among a mixture of liquids, gases, and crystals, called Kimberlite magma (after the city of Kimberley, South Africa, where diamonds were found in the 1870's). Since Kimberlite is lighter than surrounding rocks, it rises as gas from the earth's mantle, creating carrot-shaped pipes through which diamonds reach the earth's surface. 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.

Diamond Cutting: the method by which a rough diamond mined from the earth is shaped into a finished, faceted stone.
First, the diamond often undergoes cleaving or sawing to separate the rough into smaller, more workable pieces, which will each eventually become an individual polished gem.
Next, bruting grinds away the edges, providing the outline shape (for example, heart, oval or round) for the gem.
Faceting is next and is achieved in two steps:
1) during blocking, the table, culet, bezel and pavilion main facets are cut; afterward,
2) the star, upper girdle and lower girdle facets are added.
Once the fully faceted diamond has been inspected and improved, it is boiled in hydrochloric and sulfuric acids to remove dust and oil. The diamond is then considered a finished, polished gem.

Diamond Gauge: an instrument 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 their angles 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 rainbow 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'). This play of color should not be confused with a diamond's natural body color (normally white, though sometimes yellow, brown, pink or blue in the case of fancy color diamonds). A diamond's natural body color is uniform throughout the entire diamond and is constant, regardless of whether it is being tilted or not.

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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.

External Reflection: finely polished diamonds should display a high degree of external reflection. The finer the polish, the brighter and more lustrous the diamond will be. External reflection should not be confused with internal refraction, which refers to the primary light refraction that causes a diamond's fire and brilliance to occur inside its facets. External reflection refers to the light rays that are reflected back to the viewer's eye from the surface of the stone itself.

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

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