Enhancement Charts - A Reference Guide to Gemstone Enhancements

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Various Gemstones and their Possible Enhancements

GEMSTONE	CODE	ENHANCEMENT METHOD	FREQUENCY USED	STABILITY	CARE REQUIRED	SPECIAL ADVICE
Alexandrite	N	None	-----	----	Normal
Amazonite	E or W I	Impregnated with a colorless wax, paraffin or oil to improve appearance Impregnated with plastic and other hardness resins to improve appearance	Usually Usually	Good to fair Very good	Special Special	Avoid heat, chemical and ultrasonic Avoid chemicals and ultrasonic
Amber	E or H D	Heated to improve appearance, add "sun spangles" or deepen color Dyed of surface treated to add color	Usually Rarely	Very good to Good Variable	Special Special	Avoid chemicals and ultrasonic Avoid repolishing surface, chemicals and ultrasonic
Amethyst	E or H	Heated to lighten color and/or to remove "Smokey" components	Occasionally	Excellent	Special	Some unheated material may fade in long exposure to sunlight
Ametrine	N	None	----	----	Normal
Ammolite	I	Impregnated with colorless hardened substances to increase stability	Usually	Good to fair	Special	Avoid heat, household chemicals and ultrasonic
Andalusite	N	None	----	----	Normal
Aquamarine	E or H	Heated to remove yellow components thereby producing a purer blue color	Usually	Excellent	Normal
Beryl Blue Pink Yellow-Green Red Yellow	R E or H N E or O R	Irradiated blue from pale pink or colorless Heated to remove yellow component thereby producing a pure pink color None The penetration of colorless oil and resins into fissures to improve appearance Produced by irradiation	Always Commonly ----------- Commonly Usually	Poor Excellent ---------- Very good to fair Variable	Extra Special Normal Normal Special Normal / Special depending on method	Color fades, avoid light and heat Avoid high temperatures steam cleaning, chemicals and ultrasonic Certain stones may fade in light or heat depending on method
Chalcedony Agate Black (Onyx) Banded Blue Green Carnelian Jasper Chrysoprase	D D D D D E or H D D N	Dyed Dyed Dyed Dyed Dyed Heated to produce color Dyed to produce color Sometimes dyed to imitate other stones None	Usually Always Usually Commonly Usually Usually Occasionally Occasionally ----	Excellent to Good Excellent to Good Excellent Good to fair Good to fair Excellent Excellent to Good Excellent -----	Normal Normal Normal Special Special Normal Special Normal Normal	Certain stones may fade in light or heat Certain stones may fade in light or heat Certain stones may fade in light or heat
Chrysoberyl Cat's Eye Transparent Varieties: Yellow Brown Green	R N N N	Irradiated to change color None None None	Occasionally ----- ----- -----	Excellent ----- ----- -----	Normal Normal Normal Normal	For safety requirements, if neutron irradiated, refer to code letter "R" in gemstone information
Citrine	E or H	Produced by heating various types of quartz	Usually	Excellent	Normal
Coral Black White Pink Orange "Gold" Red	N E or B E or W I B D	None Bleached Impregnated with colorless wax Stabilized with plastic to improve color and durability Bleached from black coral Dyed	----- Commonly Commonly Commonly Usually Occasionally	----- Good Good Good Very Good Variable	Special Special Special Special Special Special to extra special depending on type of dye	Avoid chemicals, cosmetics and ultrasonic Avoid chemicals, cosmetics and ultrasonic: material may discolor in time Avoid chemicals and ultrasonic Same as above Avoid chemicals and ultrasonic Certain materials may fade in light or heat. Avoid chemicals, cosmetics and ultrasonic
Diamond Colorless to faint Yellow Colored	L C F HP L F R C H	Laser drilled to improve appearance Coated to disguise off-color Filling of surface cavities or fractures with a hardened substance Use of heat with pressure to alter color and/or clarity Laser drilled to improve appearance Filling of surface cavities or fractures with a hardened substance Irradiated and/or heated to induce "fancy" colors Coated to "fancy" colors Use of heat to alter color	Occasionally to common Rarely Occasionally Rarely Occasionally Rarely Occasionally Rarely Rarely	Very Good Very good to poor depending on method Very Good Unknown Very good Very good Excellent to very good Fair to poor Unknown	Normal Variable Special Normal Normal Special Normal except green Special Normal	Recutting, steam cleaning, ultrasonic and occasionally alcohol may adversely affect color and appearance Recutting or extreme heat may remove filling material Recutting or extreme heat may remove filling material Avoid heating treated green stones as the color may change. Some green stones have been radium irradiated. For safety requirements refer to the NRC. Recutting, steaming and ultrasonic may adversely affect color and appearance
Diopside (Chrome)	N	None	----	----	Special	Avoid sudden temperature changes and harsh chemicals
Emerald	E or O D	The penetration of colorless oil, wax and resins into fissures to improve appearance Dyed with colored agents	Usually Occasionally	Very good to fair Variable	Special Special	Avoid sudden temperature changes, steaming, chemicals and ultrasonic Same as above
Garnet Almandite Demantoid Grossularite Pyrope Rhodolite Spessarite Tsavorite	N N N N N N N	None None None None None None None	---- ---- ---- ---- ---- ---- ----	---- ---- ---- ---- ---- ---- ----	Normal Normal Normal Normal Normal Normal Normal	Avoid sudden temperature change Same as above Same as above Same as above Same as above Same as above Same as above
Hematite	N	None	----	----	Normal
Iolite	N	None	----	----	Normal
Ivory & Bone Mammoth (Ivory)	E or B D W I	Bleached to whiten and remove discoloration Dyed for artistic purposes Impregnated with colorless paraffin wax Impregnated with colorless hardened substances to increase stability	Commonly Occasionally Occasionally Commonly	Good Good Good Good	Special Special Special Normal	Avoid chemicals and ultrasonic: may discolor in time Same as above Same as above
Jade Jadeite Green, White and Purple Nephrite	E or W B and W B and S D D	Coated with colorless wax Two-step bleaching and wax impregnation Two-step bleaching and polymer impregnation Dyed to imitate natural colors Dyed selectively to alter color for artistic purposes in carvings	Commonly Rarely Commonly Occasionally Rarely	Fair Poor Very good to good Variable Unknown	Normal to Special Special Special Special Special	Avoid ultrasonic Avoid heat, chemicals and ultrasonic same as above Avoid strong light, chemicals and ultrasonic: may discolor in time. Avoid chemicals, ultrasonic and strong light
Kunzite	E or H R	Heated to improve color from certain locations Irradiated and heated to darken color	Commonly Commonly	Fair Fair	Special Special	Natural and/or treated materials may fade-avoid strong light, ultrasonic Same as above
Lapis Lazuli	E or W D	Coated with colorless wax or oil to improve appearance Dyed to provide color and/or uniformity	Commonly Commonly	Fair Variable	Normal to special Special	Avoid chemicals and ultrasonic Same as above
Malachite	W I	Coated with colorless wax Impregnated with plastic and/or other hardened agents to improve durability and appearance	Occasionally Rarely	Fair Good	Special Special	Avoid chemicals and ultrasonic Same as above
Moonstone	N	None	----	----	Normal
Opal White, Black & Semi-Black Matrix Boulder Fire Opal Cat's Eye Hydrophane	O I D O N I O D I	Impregnated with colorless oil, wax and resins Impregnated with colorless plastic to increase durability & improve appearance Sugar solution infilling in acid bath to darken background and enhance color play and intensity Infusion of unhardened essentially colorless substances into voids to improve appearance None Impregnated with colorless resins to give durability and improve appearance Impregnated with colorless oil, wax and resins to hide crazing Impregnated with hardened agents to improve appearance and increase durability Impregnated with colorless plastic to improve appearance and increase durability	Rarely Rarely Commonly Occasionally ---- Usually Commonly Commonly Commonly	Fair Good Good Fair ---- Good Fair Good Good	Special Special Special Special Special Special Special Special Special	Avoid ultrasonic, heat and solvents Avoid heat and solvents Avoid solvents and repolishing Avoid heat, chemicals, ultrasonic and repolishing Avoid heat Avoid heat, solvents and ultrasonic Avoid heat, solvents and ultrasonic Avoid heat and solvents Avoid heat and solvents
Pearl Natural Cultured Mabe 'Pearl'	E or B D E or B D D D R D	Bleached to improve color and appearance Dyed with or without chemical treatment combined with heat to produce gray to black. Bleached to improve color and uniformity of white color only Dyed to give rose, blue or golden overtones Dyed blue, black and other colors includes use of colored nuclei Dyed all colors (freshwater) Irradiated to produce blue, gray black and bronze colors Chemical treatment combined with heat to produce gray to black See assembled materials	Usually Rarely Usually Usually Occasionally Usually Occasionally Commonly	Very good Very good to good Excellent Good Variable Very good Very good Very good to good	Special Special Special Special Special Special Special Special Extra Special	Avoid cosmetics and household chemicals Avoid chemicals, cosmetics and ultrasonic Same as above Same as above Same as above Same as above Same as above Same as above Avoid household chemicals, cosmetics, abrasives and sudden shocks
Peridot	E or O F	Penetration of colorless oil, wax and resins into voids to improve appearance Filling of surface fractures with a colorless hardened substance	Rarely Rarely	Good to fair Good	Special Special	Avoid sudden temperature changes, harsh chemicals and ultrasonic Same as above
Rhodonite	D	Dyed to "even out color"	Occasionally	Poor	Special	Avoid chemicals and ultrasonic
Ruby	E or H D F R U	Heated to improve color and appearance (Residue of foreign substance is not visible under 10X magnification.) Dyed with colored oil to improve appearance Intentional filling of surface cavities and fractures with a foreign material, including glass which is visible under 10X magnification Irradiated to change color Diffusion of color or asterism in corundum at or near the surface	Usually Rarely Commonly Rarely Rarely	Excellent Poor Very good to fair Unknown Good	Normal Special Special Normal Special	Avoid household chemicals and ultrasonic Fracture filling in Rubies may be fragile and may fall out under extreme pressure; avoid heat and ultrasonic For safety requirements, if neutron irradiated, refer to code letter "R" Avoid repolishing or recutting
Sapphire	E or H U R	Heated to produce, intensity or lighten color and/or improve color uniformity and appearance Diffusion of color or asterism at or near the surface, usually blue Irradiation to provide temporary intense yellow or orange color	Usually Occasionally Occasionally	Excellent Good Very Poor	Normal Special Extra Special	Avoid repolishing or recutting Fades quickly in light or heat
Serpentine	D E or W	Dyed various colors Impregnated with colorless wax	Commonly Commonly	Good to fair Very good to good	Special Special	Dye may fade Avoid ultrasonic
Sodalite	D	Dyed	Rarely	Fair	Special	Dye may fade
Spinel	N	None	----	----	Normal
Spodumene Green Yellow	R R	Irradiated to produce green color Irradiated to produce yellow color	Rarely Rarely	Poor Poor	Extra special Extra special	Color fades in light or heat Same as above
Sugilite	N	None	----	----	Normal
Tanzanite	E or H	Heated to produce violet-blue color	Usually	Excellent	Special	Avoid sudden temperature changes
Topaz Blue Yellow/Orange Pink/Red Brown Green Green	R R E or H N R U	Irradiated brown and often heated to produce blue color Irradiated to intensify color Heated chromium-bearing pinkish-brown to orange stones Normal Irradiated to produce a green color Diffusion of color at or near the surface	Usually Occasionally Usually ---- Occasionally Usually	Excellent Variable Excellent ---- Poor Good	Normal Special Normal Special Extra special Special	For safety requirements, if neutron irradiated, refer to code letter "R" Avoid heat and strong light May fade in exposure to sunlight Color fades in exposure to sunlight Avoid repo