Appraisal: The value placed on a given object (diamond) in money by an appraiser

Blemish: A clarity characteristic on the surface of a diamond. Some blemishes are in the original rough diamond, a lot are the result of what happened to the diamond after it was mined.

Brilliance: The amount of light reaching the eye as a result of reflections from the internal surfaces of the facets of a diamond; the amount of light returned to the eye from the facets below the girdle.

Brilliant cut: The most popular cut for diamonds; specifically the round brilliant cut which has a round girdle outline and usually 58 facets; 32 facets and a table are above the girdle while 24 facets and a culet are below. Often the culet is omitted in which case the diamond has only 57 facets.

Carat: A standard unit of weight used for weighing gemstones; a carat equals 200 milligrams and is further divided into 100 points.

Certificate: In gemology, a written document that a stone is of a certain species, color, weight and other characteristics acceptable or not acceptable for the species in question. A certificate can also have a dollar value but not always.

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, GIA and other Gem Labs use a grading system which runs from D (totally colorless) to Z (light yellow).

Crown: The portion of a faceted gemstone above the girdle.

Culet: A small facet placed at the tip of the pavilion of a round stone or across the knife edge of the pavilion of an emerald cut stone.

Cut: This refers both to the proportions and finish of a polished diamond. As one of "the Four Cs" of diamond value, it is the only man-made contribution to a diamond's beauty and value.

Depth: The height of a diamond from the culet to the table. The depth is measured in millimeters.

Depth Percentage: This depth percentage of a diamond is important to its brilliance and value, Where that depth lies is important to the diamond's beauty; specifically, the pavilion should be just deep enough to allow light to bounce around inside the diamond and be reflecting out to the eye at the proper angle.

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 (the soft black material used to make pencils).

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.

Eye-Clean: An term used in the jewelry industry to describe a diamond with no blemishes or inclusions that are visible to the naked eye (i.e. a human eye which is not aided by magnifying devices such as a jeweler's loupe or a microscope).

Facet: The smooth, flat faces on the surface of a diamond. They allow light to both enter a diamond and reflect off its surface at different angles, creating the play of color and light for which diamonds are famous.



Fire: In faceted stones, a layman's term for dispersion. The effect, which appears as a play of small flashes of color across the surface of the diamond as it is tilted.

Flaws: Inclusions of foreign minerals, internal cleavages or fractures in a gemstone.

Fluorescence: An effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light (such as the lighting frequently seen in dance clubs). Under most lighting conditions, this fluorescence is not detectable to the eye. However, if a diamond is naturally fluorescent, it will emit a soft colored glow when held under an ultraviolet lamp or "black light." Fluorescence is not dangerous to the diamond or to the wearer; it is a unique and fascinating quality that occurs naturally in a number of gems and minerals.

Girdle: The part of a gemstone existing in a plane separating the crown and pavilion of a gemstone. The girdle is parallel to the table and is the part of the diamond with the greatest diameter. The girdle is not graded, but rather it is described by its appearance at its thinnest and thickest points. The descriptions of girdle thickness range as follows: extremely thin; thin; medium; slightly thick; thick; extremely thick.

Inclusion: A substance enclosed within a gemstone which is visible to either the naked eye or with magnification.

Pavilion: The part of a diamond which is positioned below the girdle when the gemstone is held in its normal observing position.

Point: For diamonds it is used to mean 100th of one carat; 100 points equals one carat when weighing gemstones.

Polish: Refers to any blemishes on the surface of the diamond which are not significant enough to affect the clarity grade of the diamond. Examples of blemishes that might be considered as 'polish' characteristics are faint polishing lines and small surface nicks or scratches. Polish is regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

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.

Scintillation: For diamonds this is for flashes of bright light reflected off the external surface of facets.

"Sleepy" stone: Diamonds which due to existence of many small inclusions, due not exhibit the normal brilliancy which diamonds are famous for.

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 (can not be seen by the naked eye). Symmetry is regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

Table: The large, flat facet on the crown of a faceted diamond which is parallel with the girdle of a gemstone.

Table percentage: The value which represents how the diameter of the table facet compares to the diameter of the entire diamond.

Windowed stone: A diamond improperly cut so that you see through it rather than seeing reflections off the back facets.