Diamond Glossary and Terms: Features, Cuts or Properties of a Diamond

Diamond Definitions:

Abrasion - Tiny nicks along facet junctions, producing white fuzzy lines instead of sharp crisp facet edges.

Bezel - 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 seems to come from the very heart of a 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.

Bruise - An inclusion consisting of surface crumbling, often accompanied by tiny, root like feathers.

Cavity - An inclusion consisting of a large or deep opening in the diamond.

Chip - A tiny piece missing caused by normal wear and tear, or by cutting.

Cloud - A group of tiny white inclusions that result in a milky or cloudy appearance.

Culet - The smallest facet at the bottom of the diamond.

Emerald Cut - A step cut, usually rectangular.

Excellent Cut - A GIA, EGL, and HRD-CGL grade for excellent cut and polish of brilliants.

Extra Facet - A facet placed without regard for symmetry and not required by the cutting style.

Facet - Plane, polished surface of a diamond.

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.

Faceted Girdle - Sometimes cutters polish the girdle into 32 facets.

Feather - A separation or break due to either cleavage or fracture, often white and feathery in appearance.

Flaw - An imperfection of a diamond.

Fluorescence – The mostly blue glow of a diamond in high ultraviolet lighting conditions. Ratings: none, faint, slight, medium, distint, blue, and strong blue. Strong blue fluorescence may cause the diamond to appear oily in daylight. There can also be shades of green and brown. These will annotated on the grading cert.

Fracture - A crack on the diamond's surface.

Grain Center - A small area of concentrated crystal structure distortion usually associated with pinpoints.

Hue - Pure, spectral (prismatic) color. Hues include gradations and mixtures of red, organdy, 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.

Marquise Cut - A type of fancy shape diamond, which is elongated with points at each end.

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 are blemishes, they might also 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.

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.

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 Ideal, Excellent, Very Good, Good, Fair or Poor.

Trillion Cut - A type of brilliant fancy shape that is triangular.

Diamond Anatomy and Parts:

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. This gentle slope of the facets that surround the table is what helps to create the dispersion, or fire, in a diamond. White light entering at the different angles in broken up into its spectral hues, creating a beautiful play of color inside the diamond. The crown angle also helps to enhance the brilliance of a diamond.

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.

Girdle - The outer edge or the widest part of the diamond forming a band around the diamond.

Pavilion - The bottom part of the Diamond, below the girdle.

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.

Terms:

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. This institute is the most reliable grading lab.

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.

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 less than 10X magnification. If other factors are equal, flawless diamonds are most valuable.

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 valuable.

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.

Certificate - Laminated document by a gemological institute to describe a Diamond's characteristics. May also be called a grading report or quality document.

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.

Fancy Diamond - A diamond with an attractive natural body color other than light yellow or light brown. Color wise, this will usually be Z or more yellow.

GIA - Gemological Institute of America. This institute provides one of the most reliable diamond certifications.

Loupe - Magnifying glass usually of 10X.

Zirconium - is a natural occurring metal. Synthesized in crystal form, also called cubic zirconia.