Which has comparison as follows :
AAA (A3) : 4 stars.
AA (A2) : 3 stars.
BA: 2 stars.
C : 1 star
||Very exelent quality for beads standard|
|Very beautiful, but not the most popular color|
|Common as you will see in the market|
|Not constant color in one string. Sometimes mixed color.|
||Good shape. Cut beatutifully by machine.|
|Cut beautifully. But the hole might not be straight or the hole edge might not be beautiful.|
|Not beautifully cut. The shapes might not be very round or not be symmetrically.|
Looks like cut by hand.
|Not very good. Contains a lot of inclusion. Looks cloudy.|
|N||Not enhanced. The stone has received no enhancement and the seller will provide a guarantee that there has been none.|
|B||Bleaching: The use of chemicals or other agents to lighten or remove a gemstone's color.|
|C||Coating: The use of such surface enhancements as laquering, 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: As a by-product of heat enhancement, the presence of solidified borax or similar colorless substances which are visible under properly illuminated 10X magnification.|
|G||Gamma/Electron Irradiation: The use of gamma and/or electron bombardement to alter a gemstone's color; may be followed by a heating process.|
|H||Heating: The use of heat to effect desired alteration of color, clarity, and/or phenomena. (Residue of foreign substances in open fractures is not visible under properly illuminated 10X magnification.)|
|I||Infilling: The intentional filling of surface breaking cavities or fractures usually with glass, plastic, resin with hardeners and/or hardened foreign substances to improve durability, appearance and/or add weight.|
|L||Lasering: The use of laser and chemicals to reach and alter inclusions in diamonds.|
|O||Oiling/Resin Infusion: The intentional filling of surface breaking cavities with a colorless oil, wax, natural resin, or unhardened man-made material. (Oil, man-made resin, cedar wood oil, Canada balsam, paraffin, etc.)|
|R||Irradiation: The use of neutron, requiring an environmental safety release from the Nuclear Regulatory Commission, with the combination of any other bombardement and/or heat treatment to alter a gemstone's color.|
|S||Bonding/Stabilization: The use of colorless bonding agents (commonly plastic) within a porous gemstone to give it durability and improved appearance.|
|U||Diffusion: The use of chemicals in conjunction with high temperatures to produce color and/or asterism-producing inclusions.|
|W||Waxing/Oiling: The impregnation of a colorless wax, parafin and oil in porous opaque gemstones to improve appearance.|
|Category of synthetic stones|
|SYN||Synthetic materials. The name synthetic must be accompanied by a specific reference to the actual composition.|
|IMIT||Imitations, product-simulants, subsitutes. Trade names used to promote various simulant products in these category must be accompanied by a specific reference to the actual composition of the simulant.|
|ASBL||Assembled materials, composite, doublets, triplets. Tag for products of multiple layers or combinations of manufactured and/or natural materials fused, bonded or otherwise joined together to increase stability and/or to imitate the appearence of a natural gemstone, create a unique design or generate unusal color combinations.|
The above codes and explanations were taken from the American Gem Trade Association's AGTA Source Directory 2000-2001.