Buying Guide

Pearl Facts | Ring Sizing | The 4 C’s of Diamonds | The 4 C’s of Gemstones
Diamond & Gemstone Size Ranges | Metal Types

Published by the American Gem Trade Association.

Enhancement: Any treatment process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.

N: The “N” symbol appears on the chart only for natural stones which are not currently known to be enhanced; however, the “N” symbol can also be used for other natural gemstones in the event that a gemstone has received no enhancement and the seller will provide a guarantee that there has been none.

E: The “E” symbol indicates that a gemstone has undergone its traditional enhancement process.

B Bleaching:
The use of heat, light and/or other agents to lighten or remove a gemstone’s color.
C Coating:
The use of such surface enhancements as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color, or add other special effects.
D Dyeing:
The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.
F Filling:
The filling of surface-breaking cavities or fissures with colorless glass, plastic, solidified borax or similar substances. This process may improve durability, appearance, and/or add weight.
H Heating:
The use of heat to effect desired alteration of color, clarity, and/or phenomena (if residue of foreign substances in open fractures is visible under properly illuminated 10X magnification HF should be used.
HP Heat & Pressure:
The use of heat and pressure combined to effect desired alterations of color clarity and/or phemonena.
I Impregantion:
The impregnation of a porous gemstone with a colorless agent (usually plastic) to improve durability and appearance.
L Lasering:
The use of a laser and chemicals to reach and alter inclusions in diamonds.
O Oiling/Resin Infusion:
The filling of surface-breaking fissures with colorless oil, wax, resin, or other colorless substances, except glass or plastic, to improve the gemstones appearance.
R Irradiation:
The use of neutrons, gamma rays or beta particles (high energy electrons) to alter a gemstones color. The irradiation may be followed by a heating process.
U Diffusion:
The use of chemicals in conjunction with high temperatures to produce artificial color and/or asterism-producing inclusions.
W Waxing/Oiling:
The impregnation of a colorless wax, paraffin, and oil in porous opaque or translucent gemstones to improve appearance.

Because of the rarity of naturally occurring pearls, a process of cultivating pearls was introduced in the early 1900s. In this process, a small bead of polished shell is inserted into an oyster or mollusk to act as an irritant and produce a pearl, which can take up to 24 months. These pearls are referred to as cultured pearls. Pearls are classically elegant and never go out of style.

Pearl Facts | Ring Sizing | The 4 C’s of Diamonds | The 4 C’s of Gemstones
Diamond & Gemstone Size Ranges | Metal Types