Monday, August 27, 2007

Defining Terms...

It's always important to understand the meaning of peculiar trade jargon. The following list simply defines some common diamond terminology.

American Gem Society (AGS)
American Gem Society (AGS) is an association of independent retail jewelers and suppliers that is dedicated to proven ethics, knowledge and consumer protection.

American Gem Society Laboratories (AGSL)
Established in 1996, the AGSL is the leading gemological laboratory renowned for specializing in diamonds and setting the highest standard for cut grading.

Bar Channel Setting
In a bar channel setting, individual metal bars separate each gemstone. To lock a gem in place, the metal is molded around it.

Bezel Setting
In a bezel setting, a metal rim secures a gemstone in place by the girdle. The bezel setting guards the gemstone from damage, yet does not block light from entering the top of the stone and creating brilliance.

Total brightness of light reflected from the surface and from within a diamond.

Carat Weight
Commonly referenced as the size of a diamond, carat is actually a standard unit of measure that defines the weight of a diamond. One carat is equivalent to 200 milligrams. Two diamonds of the same carat weight may appear to be different sizes depending on how well the diamond is cut. Diamonds cut to retain precious extra weight are usually smaller in diameter than a well cut diamond of the same weight.

Center Stone
The center stone is the central, dominant stone in a piece of jewelry with multiple stones.

Channel Setting
In a channel setting, ridges in the metal create a channel to hold the gemstones in place.

Gemstones are frequently sent to a laboratory for independent grading and verification against a master set of gemstones according to industry-wide guidelines.

A characteristic that makes every diamond unique is the inclusion of tiny traces of other elements or gasses that may have been trapped inside at the time the diamond was formed. These inclusions are nature's fingerprints and each diamond's birthmark. The clarity scale measures the number, size and location of these within a diamond. The most valuable and rare designation is flawless (FL).

Many diamonds appear colorless, but may actually contain very faint traces of yellow or brown. The less color a diamond has the rarer and more valuable it is. The color scale describes the degree of body color, from D (completely colorless) to Z (dark - but not fancy colored).

The crown is the area of a gemstone above the circumference – including the table, eight main facets and twentyfour brilliant facets. Light is projected to the observer through the crown in the form of brilliance, fire, and sparkle.

The culet is the tiny facet at the point of the pavilion, or bottom, of a diamond. The culet is used by cutters to center all faceting of a diamond as well as to protect the point.

Cut refers to the shape, style and finish of a diamond. The quality of the cut determines how well a diamond will reflect and refract light. The more perfectly cut – the more brilliance, fire and sparkle.

Depth Percentage
All percentage measurements are based on the diameter of the gemstone being 100%. The depth percentage is simply the height of a gemstone, measured from the culet to the table, divided by its diameter.

The flat polished surfaces on a gemstone. These surfaces act as both windows and mirrors in a diamond – allowing light to pass through and/or reflect. A round, brilliant-cut diamond has 58 facets.

The quality of each facets polish and symmetry, the condition of its girdle, and the overall precision of the cut determine a diamond’s finish.

The spectral colors of light reflected and refracted from within a diamond through its crown. Fire is maximized by cutting all 58 facets of a round brilliant diamond to the correct proportions.

Some diamonds glow when exposed to ultraviolet light. This is often very faint blue, but may occur in other colors. Subtle fluorescence that is not visible under normal light conditions does not affect the value of a diamond.

Gemological Institute of America (GIA)
GIA is the leading educational institution in the jewelry industry.

Gemological Institute of America – Gem Trade Lab (GIA-GTL)
An independent gemological lab recognized as a top authority on grading all types of gemstones.

The girdle is the thin band around the circumference or widest portion of the diamond. This edge is secured in jewelry settings and protects the diamond from damage.

A head is the part of a mounting that sets and holds the stone in place.

Head Size Range
The carat weight range of a gemstone that can be mounted into a setting's head.

Inclusions are trace minerals, fractures, and other characteristics that make up the unique internal fingerprint of a gemstone. Inclusions are created during the gem’s formation within the Earth.

Kimberley Process (KP)
The United Nations, all diamond-producing countries and non-governmental have adopted an international agreement known as the Kimberley Process (KP) to prevent traffic in “conflict” diamonds. Over 99% of the world’s rough diamonds are documented with Certificates of Origin to ensure that they come from conflict-free sources.

This term describes the absence of cross-graining or included crystals within a diamond. Diamonds have 12 polishing grains formed in an octahedron. You can only polish across one at a time to achieve adamantine finish. If the grains are crossed, twisted or knotted, then achieving a superlative polish becomes impossible.

The first two numbers of a diamond’s measurement represent its maximum and minimum diameter in millimeters. The third number represents the depth of the diamond from its culet to its table.

The pavilion is the bottom portion of a diamond, which extends from the girdle to the culet. In a classic round brilliant the pavilion consists of eight main and sixteen brilliant facets.

Polish is the term that describes the external finish of a gemstone. Because diamonds are the hardest substance known, they are capable of taking the highest level of polish known as adamantine. Poorly polished diamonds do not achieve this level of finish.

Prong Setting
In a prong setting, metal prongs are cut to fit the diamond's girdle, and then pushed securely down over the gem’s crown facets.

Proportions are the set of measurements used to describe the various angles and percentages of a finished gem diamond. They define the footprint of the diamond relative to its size. It is well known that very particular proportions create the best visual results in a diamond.

Round Brilliant Cut
Round is the shape with the highest degree of symmetry. That is why round diamonds have always been considered top performers. The brilliant cut has 58 facets. This cut makes the best possible use of light for utmost brilliance, fire and sparkle.

Commonly called "sparkle" - and known scientifically as dynamic contrast brilliance - scintillation refers to the tiny flashes of light when the diamond, the light source, or the observer moves. Scintillation is affected by the number, size, and position of all facets, as well as the quality of their polish.

A piece of jewelry that is set with only one gemstone is often referred to as a solitaire. The gemstone itself is also often referred to as a solitaire.

Symmetry describes the overall shape of a diamond as well as the alignment, shape and positioning of all its facets. Perfect symmetry greatly enhances a diamond’s ability to reflect and refract light.

System of Warranties (SoW)
In order to curb any potential for illicit trade in diamonds passing through troubled areas, a System of Warranties ensures that KP diamonds cannot be tampered with during transit. A written statement must accompany diamonds and diamond jewelry, to guarantee they are from legitimate sources.

The table is the largest facet of the diamond, located directly on the top. The table is the window through which we see most of a diamonds magic.

Table Percentage
The width of the table divided by the diameter of the diamond gives us the table percentage.