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AGS - American Gem Society-- An educational institution for gemological studies. The AGS Labs were created primarily to develop and promote universally accepted standards for grading cut. Bezel Facet - A facet on the crown, or upper part of the diamond, above the girdle. Blemish - A clarity characteristic that occurs on the surface of a diamond, which is an imperfection external to the diamond. Bow Tie Effect - An effect caused by a shadowy area visible in some fancy shapes, caused by light leaking out the bottom of the diamond. Brilliance - The brightness that emanates from the diamond. It is the effect that makes diamonds unique among all other gemstones. While other gemstones also display brilliance, none have the power to equal the extent of diamond's light-reflecting power. Moissanite is the only gemstone to display more fire and as much brilliance as a diamond. Bruise - An inclusion consisting of surface crumbling, often accompanied by tiny, root like feathers. Carat Weight - The metric carat, which equals 2 milligram, is the standard unit of weight for diamonds and most other gems. If other factors are equal, the more a diamond weighs, the more valuable it will be. Cavity - An inclusion consisting of a large or deep opening in the diamond. Certificate - Laminated document by a gemological institute to describe a Diamond's characteristics. Chip - A tiny piece missing, caused by normal wear and tear, or by cutting. Clarity - A diamond's relative position on a flawless to imperfect scale. Clarity characteristics are classified as inclusions (internal) or blemishes (external). The size, number, position, nature, and color or relief of characteristics determines the clarity grade. Very few diamonds are flawless, that means, show no inclusions or blemishes when examined by a skilled grader (under 10X magnification). If other factors are equal, flawless diamonds are the most expensive. Cloud - A group of tiny white inclusions that result in a milky or cloudy appearance. Color - Grading color in the normal range involves deciding how closely a diamond's body color approaches colorlessness. Most diamonds have at least a trace of yellow or brown body color. With the exception of some natural fancy colors, such as blue, pink, purple, or red, the colorless grade is the most expensive. Crown - The upper part of the diamond above the girdle--consists of a large flat area on top called a table, and several facets below it. Crown Angle - The angle at which a diamond's bezel facets (or, on emerald cuts, the row of concentric facets) intersect the girdle plane. The crown angles must work with the other angles to produce incredible brilliance. It is the interrelationships of the angles that create brilliance. Cut - The proportions and finish of a polished diamond (also called make). Cut can also mean shape, as in emerald cut or marquise cut. Proportions are the size and angle relationships between the facets and different parts of the diamond. Finish includes polish and details of facet shape and placement. Cut affects both the weight yield from rough and the optical efficiency of the polished diamond; the more successful the cutter is in balancing these considerations, the more valuable the diamond will be. Culet - The smallest facet at the bottom of the diamond. CZ - Zirconium is a natural occurring metal. Synthesized in crystal form it is called cubic zirconium. Commonly used as a diamond simulant. Depth - The height of a diamond from the culet to the table. The depth is measured in millimeters. Depth Percentage - There are two different measurements of a diamond's depth- the actual depth in millimeters and the depth percentage, which expresses how deep the diamond is in comparison to how wide it is. 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. EGL – European Gemological Laboratory. Generally accepted laboratory for certifications. Emerald Cut - A step cut, usually rectangular. Excellent Cut - A GIA and HRD-CGL grade for excellent cut and polish of brilliants. This is not a final determiner of brilliance. Extra Facet - A facet placed without regard for symmetry and not required by the cutting style. Can sometimes greatly improve the look of an otherwise marginal cut. It does not, in itself, determine whether a stone will be brilliant or not. Eye-Clean - A term used in the jewelry industry to describe a diamond with no blemishes or inclusions that are visible to the naked eye. This will be a different level for each person, depending on how perfect one’s vision is. Facet - Plane, polished surface of a diamond. Faceted Girdle - Sometimes cutters polish the girdle into 32 facets. This feature can improve the stone’s ability to stay clean when wearing, as the unpolished girdle can collect minute bits of oils and debris and affect the stone’s apparent color. Fancy Color Diamond - A diamond with an attractive natural body color other than light yellow or light brown. Feather - A separation or break due to either cleavage or fracture, often white and feathery in appearance. FIRE- The factor of brilliance that is the ‘rainbow’ effect. This is where you see the spectral colors of light. Flaw - An imperfection of a diamond. Fluorescence – The most often bluish glow of a diamond in high ultraviolet lighting conditions. Ratings: none, faint, slight, medium, strong blue. Strong blue fluorescence may cause the diamond to appear milky in some lights. Other colors of fluorescence can occur as well. Fracture - A crack on the diamond's surface. GIA - Gemological Institute of America. Created the original grading scale used by the industry. This institute provides generally accepted diamond grading standards. Girdle - The outer edge or the widest part of the diamond forming a band around the diamond. Grain Center - A small area of concentrated crystal structure disruption, usually associated with pinpoints. Hue - Pure, spectral (prismatic) color. Hues include gradations and mixtures of red, orange, yellow, green, blue, violet and purple. Included Crystal - A mineral crystal contained in a diamond. Inclusion - Imperfection internal to the diamond. Internal Graining - Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be colored or reflective. Loupe - Magnifying glass usually of 10X. Marquise Cut - A type of fancy shape diamond, which is elongated with points at each end and resembles a football shape. 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 can be considered blemishes, they can 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. Needle - A long, thin included crystal that looks like a tiny rod. Oval Cut - A type of fancy shape diamond, which is essentially an elongated version of a round cut. Pavilion - The bottom part of the diamond, below the girdle. Pear Cut - A type of fancy shape diamond that resembles a teardrop. Pinpoints - Miniscule spots internal to a diamond. A cluster of pinpoints can form a cloud. Pit - A tiny opening, often looking like a white dot on the surface of the diamond. Point - 100th of a carat, or .01ct. Polish Lines - Tiny parallel lines left by polishing. Fine parallel ridges confined to a single facet, caused by crystal structure irregularities, or tiny parallel polished grooves produced by irregularities in the scrape surface. Polish Mark - Surface clouding caused by excessive heat (also called burn mark, or burned facet), or uneven polished surface resulting from structural irregularities. Princess Cut - A type of brilliant cut fancy shape that can be either square or rectangular. Radiant Cut - A type of brilliant cut fancy shape that resembles a square or rectangle with the corners cut off. Surface Graining - Surface indication of structural irregularity. May resemble faint facet junction lines, or cause a grooved or wavy surface, often cross facet junctions. 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 Excellent, Very Good, Good, Fair or Poor. It is not directly related to brilliance of the diamond. Table - The flat facet on the top of the diamond. It is the largest facet on a cut diamond. Table Percentage - The value that represents how the diameter of the table facet compares to the diameter of the entire diamond. Trillion Cut - A type of brilliant fancy shape that is triangular. |
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