Diamond Glossary

The knowledge and more information you have the better diamond purchase you will make. Here are a number of diamond terms that are used by jewelers to describe diamonds and which appear on diamond grading reports.

G:

Gemological Institute of America (GIA):
Founded in 1931 by Roger Shipley, this non- profit organization upholds the highest standards for grading diamonds and other precious gems. The GIA has one of the most-respected and well-regarded gemological laboratories in the world; GIA was responsible for developing and standardizing the diamond grading system that is used today by nearly all other gem labs.

Girdle:
The outer edge, or outline, of the diamond's shape. 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. While it is less desirable for a round diamond to display an extremely thin or extremely thick girdle, such girdle widths are more common and acceptable in fancy shapes.

For example, shapes such as pears, marquises or hearts may be cut with extremely thick girdles at their points (and at the cleft, in the case of a heart) in order to protect these delicates corners from damage. Most diamonds have smooth girdles that are fashioned by a "bruter" (a diamond cutter who is responsible for shaping the diamond's basic outline) early on in the cutting process. In some cases, cutters go a step further and do additional cutting on the girdle. In these cases, they may decide to create a "polished" girdle or a "faceted" girdle. In both cases, the difference between these and a regular, smooth girdle is generally not distinguishable to the eye. A polished or faceted girdle doesn't improve a diamond's grade. Most labs grade a girdle's thickness, not its appearance.

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

Gemologist:
One who has successfully completed recognized courses of study in gem identification, grading and pricing, as well as diamond grading and appraising; e.g., a Gemologist or Graduate Gemologist of the Gemological Institute of America or a Certified Gemologist of the American Gem Society.

Girdle Facets:
The 32 triangular facets that adjoin the girdle of a round brilliant-cut stone, 16 above and 16 below. Also called upper- and lower-girdle facets, upper- and lower-break facets, top- and bottom-half facets, skew facets or cross facets. Facets are sometimes placed directly on the girdle, in which case the stone is usually said to have a faceted girdle, to have a polished girdle or to be girdle faceted.

Girdle Reflection:
When a diamond has a pavilion that is too shallow or flat, the girdle is seen reflected in the table.

Girdle Thickness:
The width of the outer edge, or periphery, of a fashioned diamond or other gemstone. In a rounded style of cutting, such as the round brilliant or pear shape, the girdle edges, when viewed parallel to the girdle plane, consist of undulating lines caused by the intersection of the flat facets with the curved girdle. In such stones, the girdle thickness is measured across the midpoints of opposing upper- and lower-girdle facets.

Girdling:
The step in the fashioning process of a diamond in which the stone is given a circular shape. The stone is held in a lathe, or cutting machine, and another diamond, called a sharp, which is affixed to the end of a long dop that is supported by the hands and under an armpit, is brought to bear against the stone behind shaped. An older method consisted merely of rubbing two diamonds together until the desired shape was obtained.

Growth or grain lines:
These can be considered internal flaws, and can often be seen only by rotating the diamond very slowly. They can appear and disappear almost instantaneously. They appear as small lines or planes within the diamond.

Gypsy setting:
The Gypsy setting is predominantly used for men’s jewelry. The band is one continuous piece that gets thicker at the top. The top is dome shaped and the stone is inserted in the middle. Click here to learn more about ring settings.

GGG:
Gadolinium Gallium Garnet, a modern imitation of a natural diamond.

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

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.

Top