Symbols for Specific Forms of Enhancement

• B = Bleaching: The use of heat, light and/or chemicals or other agents to lighten or remove a gemstone’s color. This is often accompanied by subsequent dying and/or impregnation. Example: bleached cultured pearl; bleached/impregnated jadeite (‘B-jade’)
• 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. Example: coated diamond
• D = Dyeing (staining): The introduction of coloring matter into a gemstone to give it new color, intensify existing color or improve color uniformity. Example: dyed green jadeite
• F = Filling: The filling of surface-breaking cavities or fissures with colorless glass, plastic, or some similar substance. This process will improve durability, appearance and/or add weight. Example: ruby
• Fh = Flux healing: During heat enhancement, fluxes (or heat alone) may be used to heal fractures/fissures which were formerly open. The process dissolves the walls of the fractures and redeposits the molten gem material, healing the fractures closed. Example: ruby (particularly that from Möng Hsu, Burma)
• H = Heating: The use of heat to alter color, clarity, and/or phenomena. Example: Ruby, sapphire, tanzanite, aquamarine, demantoid garnet
• I = Impregnation: The impregnation of a porous gemstone with a colorless agent (usually plastic) to give it durability and improve appearance. Example: Stabilized turquoise
• L = Lasering: The use of a laser and chemicals to reach and alter inclusions. Example: diamond
• O = Oiling/Resin Infusion: The filling of surface-breaking fissures with a colorless oil, wax, resin or other colorless substances, except glass or plastic, to improve the gemstone’s appearance. Example: emerald
• R = Irradiation: The use of neutrons, gamma, ultraviolet and/or electron bombardment to alter a gemstone’s color. The irradiation may be followed by a heating process.Example: blue topaz
• U = Lattice (‘bulk’ or ‘surface’) Diffusion: Outside-in diffusion of coloring chemicals via high-temperature heat treatment to produce color and/or asterism. Example: lattice diffusion-treated sapphire
• W = Waxing/Oiling: The impregnation of a colorless wax, paraffin and/or oil in porous gemstones to improve appearance. Example: jadeite

Natural Gemstone Enhancement Chart

(based on the AGTA Source Directory 2000–2001)

 

Natural Gemstone	Enhancement Symbol	Description Used	Frequency Encountered	Stability	Care Requirements
Agate	D	–	Usually	Excellent to good	Normal
Fire Agate	N	–	–	–	Normal
Alexandrite	N	–	–	–	Normal
Amber	E or H	–	Usually	Very good to good	*Special
	D	–	Rarely	Variable	Special
Amethyst	E or H	–	Occasionally	Excellent	*Special
Ametrine	N	–	–	–	Normal
Andalusite	N	–	–	–	Normal
Aquamarine	E or H	–	Usually	Excellent	Normal
Beryl	R	Maxixe	Always	Poor	X-Special
	R	Yellow	Usually	Variable	Special
	N	Yellow-green	–	–	Normal
	E or O	Red	Commonly	Very good to fair	Special
Chalcedony	D	Black	Always	Excellent to good	Normal
	D	Banded	Usually	Excellent	Normal
	D	Green	Usually	Good to fair	Special
	D	Blue	Commonly	Good to fair	Special
	E or H	Carnelian	Usually	Excellent	Normal
	D	Carnelian	Occasionally	Excellent to good	*Special
	D	Jasper	Occasionally	Excellent	Normal
	N	Chrysoprase	–	–	Normal
Chrysoberyl	N	Transparent	–	–	Normal
	R	Cat’s eye	Occasionally	Excellent	Normal
Citrine	E or H	–	Usually	Excellent	Normal
Coral	N	Black	–	–	*Special
	E or B	White	Commonly	Good	Special
	E or W	Pink	Commonly	Good	Special
	I	Orange	Commonly	Good	Special
	B	Gold	Usually	Very good	Special
	D	Red	Occasionally	Variable	X-Special
Natural Gemstone	Enhancement Symbol	Description Used	Frequency Encountered	Stability	Care Requirements
Diamond	L	–	Occasionally	Very good	Normal
	C	–	Rarely	Very good to poor	Special
	F	–	Occasionally	Very good	Special
	HP	–	Rarely	Unknown	Special
Diamond – Fancy	R	–	Occasionally	Excellent to very good	Special
	L	–	Occasionally	Very good	Normal
	F	–	Rarely	Very good	Special
	C	–	Rarely	Fair to poor	Normal
	H	–	Rarely	Unknown	Normal
Diopside – Chrome	N	–	–	–	*Special
Emerald	E or O	–	Usually	Very good to fair	Special
	D	–	Occasionally	Variable	Special
Garnet	N	All varieties	–	–	*Special
	E or H	Some demantoid	Commonly	Very good	*Special
Hematite	N	–	–	–	Normal
Iolite	N	–	–	–	Normal
Jade – Jadeite	E or W	–	Commonly	Fair	Special
	B and I	Green/purple/white	Commonly	Very good to good	Special
	D	–	Occasionally	Variable	Special
	B and W	–	Rarely	Poor	Special
Jade – Nephrite	D	–	Rarely	Unknown	Special
Kunzite	E or H	–	Commonly	Fair	Special
	R	–	Commonly	Fair	Special
Natural Gemstone	Enhancement Symbol	Description Used	Frequency Encountered	Stability	Care Requirements
Lapis lazuli	E or W	–	Commonly	Fair	Special
	D	–	Commonly	Variable	Special
Moonstone	N	–	–	–	Normal
Morganite	E or H	–	Commonly	Excellent	Normal
Opal	O	White/black	Rarely	Fair	Special
	I	–	Rarely	Good	Special
	O	Boulder	Usually	Good	Special
	D	Matrix	Commonly	Good	Special
	N	Fire opal	–	–	*Special
	I	Cat’s eye	Usually	Good	Special
	I/O/D	Hydrophane	Commonly	Good to fair	Special
Pearl – Natural	E or B	White	Usually	Very good	Special
	D	–	Rarely	Very good to good	Special
Pearl – Cultured	E or B	White	Usually	Excellent	Special
	D	Many colors	Usually	Variable	Special
	R	Black/gray	Occasionally	Very good	Special
Peridot	E or O	–	Rarely	Good to fair	Special
	F	–	Rarely	Good	Special
Ruby	E or H	–	Usually	Excellent	Normal
	Fh	–	Commonly	Excellent	Normal
	O	–	Occasionally	Good to fair	Special
	D	–	Rarely	Poor	Special
	R	–	Rarely	Unknown	Normal
	F	–	Commonly	Very good to fair	Special
	U	–	Rarely	Good	Special
Natural Gemstone	Enhancement Symbol	Description Used	Frequency Encountered	Stability	Care Requirements
Sapphire	E or H	–	Usually	Excellent	Normal
	U	–	Occasionally	Good to fair	Special
	O	–	Occasionally	Good to fair	Special
Sapphire – Fancy	E or H	–	Usually	Excellent	Normal
	R	Yellow/orange	Occasionally	Very poor	X-Special
	O	–	Occasionally	Good to fair	Special
	U	–	Occasionally	Good to fair	Special
Serpentine	D	Various colors	Commonly	Good to fair	Special
	E or W	–	Commonly	Very good to good	Special
Spinel	N	–	–	–	Normal
	O	–	Occasionally	Good to fair	Special
Sugelite	N	–	–	–	Normal
Sunstone	N	–	–	–	Normal
Tanzanite	E or H	–	Usually	Excellent	*Special
Topaz	R	Blue	Usually	Excellent	Normal
	R	Yellow/orange	Occasionally	Variable	Special
	R	Green	Occasionally	Poor	X-Special
	U	Green	Usually	Good	Special
	N	Brown	–	–	*Special
	E or H	Red/pink	Usually	Excellent	Normal
Natural Gemstone	Enhancement Symbol	Description Used	Frequency Encountered	Stability	Care Requirements
Tourmaline	N	Chrome green	–	–	Normal
	N	Cat’s Eye	–	–	Normal
	E or H	Yellow/orange	Rarely	Excellent	Normal
	R	Yellow/orange	Rarely	Very good	Normal
	E or H	Green/blue	Commonly	Excellent	Normal
	O	Any color	Occasionally	Good to fair	Special
	E or H	Pink/red/purple	Occasionally	Excellent	Normal
	R	Pink/red/purple	Commonly	Good	Normal
	D	Pink/red/purple	Occasionally	Fair to poor	Special
Turquoise	W	–	Commonly	Fair to poor	Special
	D	–	Rarely	Poor	X-Special
	I	–	Commonly	Good	Special
Zircon	N	Green/brown	–	–	*Special
	E or H	Blue/colorless	Always	Fair to poor	Special
	E or H	Yellow	Rarely	Good	Special
	E or H	Red	Commonly	Fair to poor	Special

Notes:

• The “N” symbol is used only for gemstones that we guarantee have not been enhanced.
• All jewelry (with or without stones) requires special care; some jewelry requires extra-special
  (X-Special) care.
• * Indicates a gemstone that generally requires special or extra-special care (although the need for care is not necessarily related to the enhancement).