Diamond Glossary
(See Illustration Below For a Visual Representation of the Glossary) |
| AGS-American Gem Society A professional jeweler's society founded in 1934. AGS has a laboratory which grades diamonds and offers a diamond grading report. AGS has a diamond cut grading system for round diamonds. |
| AGS Cut Grading Scale 0 Ideal 1 Excellent 2 Very Good 3-4 Good 5-7 Fair 8-10 Poor |
| Bezel Facet On a round brilliant diamond, these are eight large kite-shaped facets on the crown. Also called top main facet. |
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Brightness |
| Brilliance Describes the reflections of white light coming from the diamond. It is an essential attribute of a beautiful diamond and it has 2 components; brightness and contrast It appears brighter, especially when it is moved because it 'scintillates'. |
| Brilliant Cut Diamond Round diamond with 57 facets (58 if there is a culet). Round Brilliant cut diamonds are more brilliant than any of the fancy-shaped stones. |
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Carat |
| Cavity A type of inclusion consisting of a large or deep opening in the diamond is called a cavity. |
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Clarity
* Flawless (FL) |
| Cleavage A break in a diamond which is parallel to one of its crystallographic planes. A cleavage may be caused by inherent internal strain or by a sharp blow. The break may extend to the surface of a diamond. |
| Cloud A group of tiny, white inclusions which give a "cloudy" appearance. |
| GIA Diamond Color-Grading Scale The GIA's Diamond Color-Grading Scale is the industry's most widely accepted grading system. The scale begins with the letter D, representing colorless, and continues, with increasing presence of color, to the letter Z. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions. Many of these color distinctions are so subtle that they are invisible to the untrained eye. But these slight color differences make a very big difference in diamond quality and price. NADB only represents diamonds with colors ranging from D to J. |
| Crown The part of the diamond that is above the girdle. It consists of the table and the crown facets below it. |
| Crown Angle 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 The part of the diamond that is above the girdle. |
| Crown Height % 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. |
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Culet The culet size is listed on a cert and your diamond's culet should be pointed (no culet), very small, small or medium because these are Large to extremely large culets may be visible to the naked eye and can look like an inclusion. |
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Cut |
| Dealer Asking Price This is the price the dealer or owner would like to sell the diamond for. We are often able to negotiate a lower selling price for our clients. |
| Depth % Total depth (measured from the table plain to the culet) relative to the average diameter. Reported to the nearest tenth of a percentage point (0.1%). |
| Depth Percentage The depth of the diamond divided by the average width. |
| Dispersion The fiery, rainbow colors emanating from a diamond as white light is broken-up into colors. |
| Facet The polished planes on the surface of a diamond are the facets. |
| Feather A fracture in a diamond that looks like a white feather. |
| Fire The appearance, or extent, of spots of light dispersed into spectral colors seen in a polished diamond when it is viewed face-up. |
| Fluorescence Is the property in many diamonds that makes them glow in an environment rich in ultraviolet light. Diamonds can fluoresce in a number of colors, but generally all but blue are to be avoided. Faint to medium fluorescence is rarely detected under ordinary lighting conditions. Strong or very strong fluorescence may make a diamond appear "milky" or "oily", especially in sunlight. Blue fluorescence may enhance the color of diamonds rated "H" in color or below (I,J, etc.) by hiding their yellow tint. Diamonds rated D-F with medium+ fluorescence may sell at a discount. |
| Fracture A chip or break on a diamond that is not in the direction of a cleavage plane. Irregular in shape, they usually appear step-like or as a splinter. |
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GIA-GTL |
| Girdle The outer edge of a diamond which forms a band around the stone. The girdle can be faceted, polished or unpolished |
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Girdle Thickness |
| Diamond Grading Report Sometimes called a "certificate", although labs do not "certify" diamonds. The grading report, issued by an independent laboratory, should accurately describe the proportions, weight, color, clarity, symmetry, polish and possible fluorescence seen in the diamond being evaluated. Some labs such as GIA and AGS are felt by many experts to be more consistent and stringent in their grading than some other labs. |
| Inclusion A naturally-occurring imperfection in a diamond. Some examples are: feathers, crystals, needles, clouds and pinpoints. |
| Length-To-Width Ratio A comparison of the length and width of the girdle outline on fancy-shaped diamonds. The ratio is found by dividing the length of the diamond by the width. The width is always stated as 1. Some L to W ratios are considered to be more appealing than others, but this is a matter of personal preference. Pear 1.50 - 1.75 : 1 Marquise 1.75 - 2.25 : 1 Heart 1.00 - 1.02 : 1 Oval 1.33 - 1.66 : 1 Emerald 1.50 - 1.75 : 1 Radiant/Princess 1.00 - 1.05 : 1 |
| Lower-Girdle Facet The facets on the pavilion of a round brilliant just below the girdle. |
| Natural These blemishes can be found on some polished diamonds when some of the rough is left on the diamond. This is often done so the cutter can maximize weight in a diamond. |
| Pavilion The portion of the diamond below the girdle. |
| Pavilion Angle The angle measured between the girdle and the pavilion main facet. |
| Pavilion Main Facet The eight facets found on the pavilion of a round brilliant diamond. Their points touch the girdle. |
| Pinpoints Very small inclusions in a diamond. |
| Points 1/100th of a carat. For example, a 1/4 carat diamond weighs 25 points. |
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Polish Poorly polished facets may reduce the intensity of light reflected from, or refracted into and out of a diamond. Labs assess polish by examining the diamond, facet by facet, with reflected and a microscope; you or I may not see any difference. But there is a price difference. At NADB we choose to sell only diamonds with Very Good or Excellent polish grades. |
| Scintillation Sparkle: The appearance, or extent, of spots of light seen in a polished diamond when it is viewed face-up that flash as the diamond, observer, or light source moves. Pattern: The relative size, arrangement, and contrast of bright and dark areas that result from the internal and external reflections seen in a polished diamond when it is viewed face-up while that diamond is still or moving. |
| Star Facet One of the eight triangular facets found on the upper crown section (next to the table) of a brilliant-cut diamond. |
| Diamond Symmetry Most labs grade diamond symmetry as Excellent, Very Good, Good, Fair or Poor. On a GIA report, the basis of lab grading includes microscopic examination to ensure that facets meet perfectly; this can result in very different results. At NADB we choose to sell only diamonds with Very Good or Excellent symmetry grades. |
| Table The largest facet which sits on top of a diamond. This is where most of the light enters and exits a diamond. |
| Table % Round Brilliants - Average table size relative to the average diameter, reported to the nearest whole percentage point (1%). Fancy Shapes - Average table size relative to the width or shortest distance across the top, reported to the nearest whole percentage point (1%). |
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Total Depth % |
| Diamond Upper-Girdle Facet One of the 15 facets found on the lower crown portion of the diamond (abutting the girdle). |
Diamond Anatomy |
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Information courtesy of the GIA and Pricescope.com
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