Diamond Dictionary

 Table, Crown, Girdle, Pavilion, Culet, Facet

AGS- The American Gem Society, founded by Robert M. Shipley in 1934, is a non-profit professional organization of jewelers in the US and Canada. Its goal is to encourage ethical practices, advance knowledge and improve and maintain the image of the jewelry industry. AGS maintains the AGS Labs to develop and promote acceptable standards for grading a diamond's cut.

Bezel setting  - A setting technique, which the diamond is completely surrounded by metal.

Blemish - A flaw on the surface of a diamond, either found on the original rough or caused after the stone has been mined.

Brilliance - The brightness or reflective characteristics of a diamond. Brilliance is created when light enters the diamond at the top, bounces off the pavilion facets and is reflected through the table back to the viewer.

Brilliant cut - Developed in 1919 by renowned diamond cutter Marcel Tolkowsky, this symmetrical diamond cut containing 58 facets is the result of a precise mathematical formula. Rounds, pears, ovals, marquises, princesses, hearts and radiants all use this category of cut.

Briolette - A pear-shaped stone often used as a drop on earrings and pendants, it is cut using crossing bands of triangular facets.

Carat - The unit of weight for diamonds. The metric carat, as it is technically termed, is divided into 100 points and is equal to .2 grams.

Carbon spots - Black inclusions in a diamond that can range from microscopic pin spots to large, readily visible inclusions of non- crystallized carbon. Although carbon spots may appear as "black spots," they are neither black nor carbon, but are in fact foreign matter entrapped in the diamond during crystal growth or simply reflections of light by cleavages.

Channel setting - A setting technique in which two sides of the diamond are held in place with bars of metal. The channel setting resembles a railroad track with the diamonds running down the center. Channel settings are most often used for round brilliant, baguette, or princess cut diamonds.

Cleavage - One of two methods by which cutters split rough crystals prior to the cutting process. Cleavage is sometimes referred to as an open fissure at the edge of a diamond.

Color grading - The process by which a diamond is assessed to determine its color, which may involve comparing the diamond to a set of master color stones.

Crown - This refers to the upper part of a diamond, above the girdle. On most round and fancy shape cuts, the crown contains the flat table surrounded by bezel or star facets. On emerald cuts and step cuts, the crown consists of the concentric rows of facets from the table to the girdle.

Culet - this is where the pavilion facets meet at the bottom of a diamond. All diamonds have culets. Sometimes there is a culet facet, called a "ticked" culet and sometimes there is not.

Culet stated in laboratory reports by the following abbreviations: N - None and F or FAC - Faceted

Diamond - A crystal composed completely of carbon atoms.

Diamond cutting - is really a misnomer and should be thought of as diamond processing. A diamond is ground not cut. It is only cut when the rough is sawed or sawn in preparation for bruting. Bruting is the process where a diamond is girdled and the 4 or 8 basic facets are ground on in preparation for brilianteering, which applies all the remaining small facets that complete a diamond cut.

Dispersion - Also known as a diamond's "fire," dispersion is the play of colors seen when the diamond is moved. It is a prismatic effect that breaks visible white light and disperses it into a spectrum. Dispersion is achieved only when a diamond is correctly proportioned geometrically.

Emerald cut - An elongated square or rectangular cut, the emerald shape is eight-sided with step-cut sides and notched corners. There are usually three concentric rows of facets on the crown, another three around the culet.

Eye clean - A diamond that is free of imperfections when viewed by the naked eye. Clarity grades of this diamond range from VVS1 to SI2.

Facet - The tiny flat planes on the surface of a diamond that are precisely placed at different angles in order to allow light to enter and be reflected off of each other to create brilliance. The shape and placement of facets differ slightly depending on the shape of the diamond.

Fancy shape - A diamond shape other than round. Among the most popular fancy shapes are marquise, pear, oval, heart, trilliant, emerald, princess and radiant.

Finish - A diamond grade that is based on every aspect of a diamond's appearance, including its design, cut and polish.

Fluorescence - An effect caused when a diamond absorbs ultra- violet light. When ultraviolet light is used to illuminate a diamond, a soft, colored glow appears in some diamonds and other gemstones. Blue fluorescence enhances the color of diamonds when viewed in natural and artificial lighting conditions that contain some ultraviolet in the source. Incandescent light does not have any ultraviolet light in it. The quality of fluorescence is often only detectable by an expert.

Blue fluorescence can have a subtle affect on transparence and color appearance, especially when viewed table down. When viewed table up, diamonds with fluorescence often appear to have better color! The positive effects of fluorescence are more noticeable in lower colors, such as I-K.

Fluorescence is a much-misunderstood quality of diamonds and the lack of understanding causes some people to shy away from it. A GIA study challenged the industry notion that fluorescence has a negative effect on better color diamonds. GIA found that other than milky fluorescence, most fluorescence has minimal negative affect on diamonds. In fact, GIA maintains that if diamonds are graded accurately, those with blue fluorescence will have their colors improve in normal daylight, which contains some ultraviolet light. Blue fluorescent diamonds are more rare than non-fluorescent diamonds.

Stated in laboratory reports by the following abbreviations:

N — None

VSLT — Very Slight

SLT — Slight

Medium — Medium

STRNG — Strong

VSTRNG — Very Strong

Usually each of these is followed by BLUE or in very rare cases YELLOW

 

Flush or rub setting - A setting technique in which the top of the diamond is flush with the surface of the metal. This is a popular setting for small stones and is frequently used in men's jewelry.

GIA  - Robert M. Shipley established GIA - The Gemological Institute of America, based in Carlsbad California, in 1931. It is an educational institution devoted to all phases of the gemstone industry and includes gem-testing laboratories and gemological research and development, as well as on-campus and correspondence professional gemological training courses.

Girdle - The widest part of a diamond, with 32 facets above it and another 24 below in the traditional brilliant cut. The other 2 facets are the table and culet.

Stated in laboratory reports by the following abbreviations:

VTHN - Very Thin

THN - Thin

MED - Medium

STHK - Slightly Thick

THK - Thick

VTHK - Very Thick

F or FAC – Faceted

 

Heart shape - A diamond cut in the shape of a valentine that is actually a pear with a notch at the top. Because of its romantic connotation, the heart shape is popular for engagement rings and pendants.

Inclusion - A tiny imperfection in a diamond, an inclusion can be a spot, a bubble or a line that varies in size from microscopic to clearly visible. Generally, the more inclusions, the less valuable the stone, but as long as the inclusions do not affect the stone's ability to reflect light, they do not affect the stone's value or beauty.

Karat - A measure of purity; karat is the ratio of fine gold to an alloy. Pure gold is 24 karat, 18-karat is 18/24ths or 75% gold, 14- karat is 14/24ths, or 58.5% fine gold.

Marquise cut - A popular diamond shape that is a variation of the round brilliant, a marquise has an elongated, double-pointed shape. Oval cut - An elongated round, the oval is an even, symmetrical design that is flattering to a woman with small hands or short fingers because its shape gives the illusion of length. An oval can vary from short to long in shape.

Pavé setting - A term derived from the French word for paving a street, in this case, paving a surface with tiny diamonds. Pave is technique for setting small diamonds very closely together so that they resemble a continuous surface of diamonds. Pave is often used as an accent around a larger stone or over a large surface, providing a continuously sparkling design that covers the metal below it.

Pavilion - The bottom most part of a diamond from below the girdle to the culet.

Pear cut - This is a hybrid cut that combines the oval with the marquise, resulting in a teardrop shape. While a pear shape is beautiful in a ring, it is even more dazzling in earrings or a pendant.

Point - A unit of measurement for the size of a diamond. One hundred points equals one carat. Therefore, 50 points equals a half- carat; 25 points equals a quarter carat, etc.

Polish - Term referring to the facets' smoothness after removal of some of the microscopic grooves that develops in the cutting (grinding) of the diamond in the finishing process. An indicator of the quality of a diamond's cut, polish is graded as Ideal, Excellent, Very Good, Good, Fair or Poor.

Stated in laboratory reports by the following abbreviations:

X — Excellent

VG — Very Good

G — Good

F — Fair

P — Poor

 

Princess cut - A four-sided brilliant-cut fancy shape that can be either square or rectangular, the princess cut has become highly popular for use in engagement and fashion rings.

Prong setting - A setting technique utilizing anywhere from two to more than six claws of wire to hold the diamond in place.

Radiant cut- A square or rectangular cut that combines the shape of the emerald with the faceting pattern of the brilliant. Requires more weight to be directed toward the stone's depth.

Semi-mount - A ring mounting set with small side stones but missing the yet-to-be-set center stone.

Single cut - A basic diamond cut containing 16 facets, eight at the top, eight at the bottom, plus the table and the culet. This cut was widely used in the 20th century, primarily on small diamonds; in order to save the labor and cutting costs required finishing the diamonds from 18 to 56 facets.

Shape - Not to be confused with cut, shape refers to the outside form of the diamond. In addition to the popular round shape are fancies such as marquise, pear, oval, heart, princess, etc.

Step cut - A diamond cut in which the facets are arranged in concentric rows around the table and the culet.

Symmetry - An indicator of the quality of a diamond's alignment of facets, symmetry is graded as Excellent, Very Good, Good, Fair or Poor. A diamond lacking good symmetry will have misaligned facets with inaccurate facet junctures, a quality often invisible to the naked eye, but which can result in a loss of brilliance.Stated in laboratory reports by the following abbreviations:

X — ExcellentF — Fair

P — Poor

 

Table - The large top facet of a diamond, it is measured from side to side. Some laboratories describe ideal cuts of which one component is a table between 53% and 57% of the diameter of the girdle. There can be lovely diamonds with tables of 63%, which can be equally as brilliant providing all the other characteristics of the cut conform. The most common argument is that a very small table on a diamond gives the illusion that the diamond appears smaller than a diamond of equal diameter with a larger table.

Tiffany setting - A six-prong setting for a diamond solitaire, usually round in shape with slender prongs that flare out from the base. This style was introduced by Tiffany & Co. in 1886, but is now widely used.

Trilliant/Trillion cut - A three-sided triangular-shaped cut that uses the cutting principals of the brilliant. It was named by the founder of a company of the same name, but the company was forced to change its name because Trillion became a generic term. Trilliant is another name for the same cut, used by another firm that marketed similar stones and did not wish copyright litigation.