Abrasion: Damage to the culet or facet edges usually caused by contact with other diamonds.

Age: The age of a diamond ranges between 1000 to 3,300 million years.

AGS: American Gem Society, Las Vegas, USA

Beard: Feather-like inclusions located on the girdle resulting from poor bruting.

Bezel: Angled surface located on the crown of a stone between the girdle and table.

Bezel Facet: Four sided facets found on the bezel of a brilliant cut.

Bow Tie: Term used to describe the dark area located across a table sometimes found in fancy shapes
(aka 'Butterfly').

Brilliance: Intensity of the light reflecting out of the stone through the crown (aka 'Dispersion', 'Fire').

Brilliant: Symmetrical cut with a round girdle outline, featuring 56 facets.

Brilliant Cut: Collective name for diamond cuts whose lower facets radiate from the center of the stone towards the girdle, the most common of which is the round cut.

Butterfly: Term used to describe the dark area located across a table, sometimes found in fancy shapes (see 'Bow Tie').

Cape (Color): Term used to describe yellow diamonds found in the M to Z range of the color grading scale.

Carat: Standard weight unit for gemstones; 1 carat = .2 grams

Cavity: An opening or indentation on the surface of a diamond (see 'Pit').

Certificate: Document provided by an accredited laboratory stipulating the stone's weight , color, clarity, proportions and finish grade.

Clarity: A stone's relative freedom from inclusions and imperfections. Expressed in a fixed grading scale.

Cleavage / Gletz / Feather: A break or fracture in the stone which may be internal or external. These usually occur along the crystal's growth planes (see also 'Cleavage' 'Gletz', and 'Feather').

Cloud: A milky area in a stone made up of a multitude of small inclusions. This phenomenon may be local or spread throughout the stone.

Color: This may range from white to brown and is defined by a standard nomenclature ('grading scale'), ranging from D to Z.

Crown: The part of the stone located above the girdle.

Crystal Inclusion: An impurity within a stone with a geometric, crystal- like shape.

Culet: The small facet on the point of the pavilion.

Cut: The proportions, make and finish of a polished diamond or the actual shape of the stone.

D: The highest colour grade on the international colour grading scale. Very white.

Dark Centre: A dark area visible through the table in a stone of sub-standard make, i.e. stone is too deep.

Dark Inclusion: An impurity in the stone which is dark in color (normally black).

Dead Stone: A stone so heavily included that there is no brilliance.

Depth: The height of a diamond measured from culet to table.

Diamond: A carbon based mineral created under extreme pressure and temperature. Diamond is the hardest of all known substances and exists in a variety of colours ranging from white to fancy colors.

Dispersion: Intensity of the light reflected out of the stone through the crown (see 'Brilliance' and 'Fire').

European Gemological Laboratory (EGLUSA): Grading Lab in New York

Emerald Cut: Rectangular or square step cut with diagonally cut corners.

External Characteristics: Imperfections located on the surface of a stone.

Extra Facet: Any facet added to the stone which is in excess of the facets normally required to complete the polishing. Usually found along the girdle to remove any imperfections.

Facet: Flat polished surface on a polished stone.

Faceting: The process of polishing facets onto a stone.

Fancy Color: A naturally colored diamond with varying degrees of rarity. Yellow, Pink, Brown are some examples. Colored diamonds also come in color grades called Light Fancy, Fancy, Fancy Intense and Vivid Fancy.

Fancy Shape: Any other shape besides the brilliant cut.

Feather: A break or fracture in the stone which may be internal or external. These usually occur along the crystal's growth planes (see also 'Cleavage' and 'Gletz').

Finish: The quality of the diamond's polish.

Fire: Intensity of the light reflecting out of the stone through the crown (see 'Brilliance' and 'Dispersion').

Fisheye: A diamond whose pavilion is too shallow and, as a result, a circular reflection of the girdle is seen through the table.

Flat Stone: A stone with a shallow crown or pavilion.

Fluorescence: A visible light occasionally emitted from diamonds when exposed to ultraviolet light, usually blue in color. The visible effects of fluorescence grades of faint, inert, negligible, and medium, can only be detected by a trained gemologist. A fluorescence grade of strong or very strong can make a diamond with a near-colorless grade look even whiter yet in some instances give the diamond a slight hazy or oily appearance. Diamonds with a strong or very strong fluorescence are priced slightly lower than other diamonds.

Four C's: Carat, Cut, Color and Clarity: the four factors determining the value of a diamond.

Gem / Gemstone: Mineral or organic material with sufficient beauty, rarity and durability to be set into jewelry.

GIA: Gemological Institute of America, Carlsbad, CA

Girdle: The edge located between the pavilion and the crown which travels around the entire stone. Girdles are usually faceted.

Grain: Weight unit equivalent to 0.25 carats. (i.e. 1.00 ct stone is a four-grainer)

Graining: Irregularities in the crystal structure of a stone which show up as faint lines. These travel throughout the stone and may be internal or external.

Hardness: A stone's resistance to wear and scratching measured on Mohs hardness scale. A diamond's hardness is 10, which is the hardest on the scale.

Heart Shape (H.S): Modified brilliant cut with a heart-shaped girdle outline, featuring 56 facets.

Hearts & Arrows: A stone polished to ideal proportions with exceptional symmetry and polish which shows eight heart shapes (Pavilion) and eight arrows (Crown) when observed through a special viewer.

HRD: Certification company Diamond High Council.

IGI: Certification and Appraisal company International Gemological Institute.

Imperfection: Blemish located within the stone, occasionally reaching the exterior.

Included: Clarity grade, referring to eye visible imperfections, existing in I1,I2,I3

Inclusion: Internal imperfections that effect the clarity grade of a diamond .

Industrial Diamonds: Non-gem quality diamonds used in drills and other tools.

Internal Reflection: The reflection of a feature within a stone.

Kimberlite: Volcanic diamond-bearing rock (also called blueground).

Laser Cut: Using a laser to fashion the diamond's eventual shape, allowing cuts across the growth plains, thus permitting odd shapes such as letters, horse heads etc.

Laser Inscription: Using a laser to engrave identifying text or numerals, most commonly found on the girdle.

Leveridge Gauge: Tool used to measure the precise dimensions of a mounted or un-mounted stone.

Lively Stone: A stone with good brilliance and luster.

Loupe: Small magnifying glass used in the diamond trade to examine diamonds. Magnification may vary, but all diamonds are graded under 10X.

Loupe Clean: When viewed under magnification 10X, a stone is considered loupe clean if no imperfections are seen.

Lower Girdle Facet: Triangular shaped facets, located on the pavilion.

Lower Main Facet: Eight, four sided facets meet at the center to form the culet (syn. 'Pavillion facet')

Make: The quality of the symmetry and finish of a polished stone.

Marquise: Symmetrical boat-shaped, brilliant cut with pointed ends.

Masterstones / Color Samples: A set of polished stones which have been colour graded by an accredited laboratory for the purpose of color grading polished diamonds.

Measurements: The diameter, width, and depth of a diamond in millimeters.

Microscope: Magnifying instrument used to determine clarity in gemstones.

Mohs: Scale used to determine the hardness of minerals. A diamond is the hardest at 10 and talc is the softest at 1.

Natural: Original surface of the rough stone left on the polished stone. This is usually found on the girdle.

Nick: Small chip on a diamond usually as a result of contact with other stones.

Open Table: An inclusion which breaks the surface of the stone and shows a small pit.

Oval: Modified brilliant cut with an oval shaped girdle outline.

P.C.: Abbreviation for "Per Carat"

Parcel Paper: Folded sheets of paper used to contain polished or rough diamonds.

Pavilion: The section of the diamond found below the girdle.

Pavilion Facet: Eight, four sided facets meet at the centre to form the culet (syn. 'Lower main facet')

Pear Shape (P.S): Asymmetrical cut with one pointed and one rounded end with a pear-shaped girdle outline, featuring 56-58 facets.

Pinpoint Inclusion: Very small inclusion which may be black or white in colour, yet is not distinguishable as a crystal. When clustered together, they are called a group of pinpoints.

Pit: Tiny opening on the surface of a polished stone (see 'Cavity').

Point: Weight unit. 1 point is 1/100 of a carat.

Pointer: Term used to describe polished stones under a carat.

Polish: The degree of polish on a finished stone. For the highest grade of polish, look for an ideal (ID), excellent (EX), or very good (VG) AGSL graded diamond, and an excellent (EX) or very good (VG) GIA graded diamond. For the best balance of price and quality, look for a GIA or AGSL polish grade of good (G). Avoid diamonds with polish grades of fair (F) or poor (P), as the quality of their polish may affect the brilliance of the diamond.

Polishing Lines: Small, parallel indentations left on facets during the polishing process.

Princess: Modified brilliant cut with a square or rectangular girdle outline, featuring 57 facets.

Proportions: The relative symmetry of angles and measurements of a polished diamond.

Quality: Term used to describe the overall color, clarity and cut attributions of a stone.

Reflection: The bouncing back of light when it strikes an external or internal facet on a polished diamond.

Rough: (Stone or Diamond) Diamond of industrial or gem quality before it undergoes any manufacturing process.

Round Cut: Round brilliant cut.

Scratch: The damage to a polished stone which appears as a faint white line, due to contact with other diamonds.

Star Facet: A triangular facet located on the crown of a brilliant cut next to the table, of which there are eight.

Symmetry: The accuracy with which the diamond is polished to its perfect proportions. For the highest grade of symmetry, look for an ideal (ID), excellent (EX), or very good (VG) AGSL graded diamond, and an excellent (EX) or very good (VG) GIA graded diamond. For the best balance of price and quality, look for a GIA or AGSL symmetry grade of good (G).

Synthetic Diamond: A non-natural diamond which has been produced by man.

Table: Large facet in the center of the crown on a polished diamond.

Thermal Conductivity: The ability of a material to conduct heat. Diamonds have the highest conductivity of any material.

Ultraviolet: Lower end of the light spectrum which is invisible to the human eye and allows fluorescence to be visible in a diamond.

Upper Girdle Facet: Triangular facets located on the lower part of the bezel, right above the girdle.

Wavy Girdle: A girdle which has been improperly polished and does not run evenly.

Weight: Diamond weight is measured in carats, subdivided in grains and points.

Well Made: A well proportioned, polished diamond with a good finish.

White: A term used to describe the diamonds that are H color and up.