The history of treating gemstones with a variety of methods to improve their appearance goes back thousands of years. Today, gemstones are commonly treated to improve their color, clarity and/or durability. These treatments are various, common and acceptable in the industry as long as disclosure of the treatment is made to the buyer. It is estimated as many as 99% of rubies, sapphires and emeralds are treated, and verified un-treated examples in finer qualities command a premium price over the treated varieties.

Many popular gem types are treated, and all permanent techniques are universally accepted, again, as long as disclosure of the treatment is made to the buyer. Please note that the term "natural gemstones" refers to those formed in the earth, whether or not they have been treated after mining. These are distinctly different from "lab created", "man made" or "synthetic" gems which must be clearly labeled as "man made materials" and not "natural gemstones" according to Federal Trade Commission (FTC) law. Gemstones which are a combination of natural and man made materials must be declared as "assembled stones". Click Here to see a list of Various Other Treatments.

Gemstone types Treatments and benefits Care instructions Agate (see Chalcedony) Routinely heated, bleached or dyed to improve color Normal care Alexandrite Not routinely enhanced Normal care Almandite (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Amazonite Impregnated with wax, oil, plastic or colorless hardened resins to stabilize and improve appearance Avoid heat, household chemicals and ultrasonic Amber Routinely heated or dyed to deepen or add color Avoid chemicals, steam and ultrasonic cleaning Amethyst (Quartz) Routinely heated and/or irradiated to improve color Normal care Ammonite (Ammolite) Impregnated with colorless hardened resins to stabilize and improve appearance Avoid heat, household chemicals and ultrasonic Ametrine (Quartz) Routinely heat- treated to improve color Normal care Andalusite Occasionally heat-treated to improve color Normal care Apatite Occasionally heated to improve color Avoid chemicals, steam and ultrasonic cleaning Aquamarine (Beryl) Routinely heated to improve color Normal care Aventurine (Quartz) Occasionally dyed to improve color Normal care Azurite Occasionally filled with epoxy or resin to stabilize and improve surface appearance Avoid chemicals, steam and ultrasonic cleaning Azure-malachite Rarely filled with epoxy or resin for smoother surface and improve durability Avoid chemicals, steam and ultrasonic cleaning Bixbite (red beryl) Routinely oiled or resin treated to improve clarity Avoid heat, household chemicals and ultrasonic Topaz Usually irradiated and heated to produce color Normal care but avoid sudden temperature changes Canary Aqua ™ Routinely irradiated to enhance color Normal care but avoid excessive heat. Cat's Eye Chrysoberyl Rarely irradiated to darken color Normal care Chalcedony Routinely heat-treated, bleached and dyed to induce different colors Normal care Chrome Diopside Not routinely enhanced Avoid chemicals and sudden temperature changes Chrysoberyl transparent varieties (yellow, green, brown) Not routinely enhanced Normal care Chrysoprase Not routinely enhanced Normal care Citrine (Quartz) Routinely heat-treated to improve color Normal care Coral Routinely dyed, bleached and/or impregnated with wax, plastic or resin to improve color and stability Avoid chemicals, steam and ultrasonic cleaning Demantoid (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Diamond - colorless Occasionally laser drilled and then filled with lead glass to improve clarity. Occasionally fracture filled with lead glass to improve clarity. Occasionally HTHP treated to improve color Normal care Diamond - colored Often irradiated to improve color Normal care Emerald (Beryl) Routinely oiled or resin treated to improve clarity Avoid chemicals, steam and ultrasonic cleaning Fluorite Routinely heated and/or irradiated to improve color Avoid chemicals, steam and ultrasonic cleaning Garnet (also listed by type) Not routinely enhanced Normal care but avoid sudden temperature changes Gaspeite Occasionally stabilized with plastic Normal care Goshenite Not routinely enhanced Normal care Heliodor Irradiated to improve color Normal care Hematite Not routinely enhanced Normal care Hessonite (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Howlite Routinely dyed to improve color and to emulate turquoise Avoid steam and ultrasonic cleaning Indicolite (Tourmaline) Routinely heat-treated to improve color Normal care but avoid sudden temperature changes Iolite Not routinely enhanced Normal care but avoid sudden temperature changes Jadeite Type “A” Not routinely enhanced in higher qualities. Lower grades routinely filled with wax to reduce visibility of cracks and improve surface appearance Type “B” Routinely bleached and dyed. Routinely filled with wax to reduce visibility of cracks Normal care Jasper Occasionally dyed to enhance color Normal care Jet Not routinely enhanced Avoid steam and ultrasonic cleaning Kornerupine Not routinely enhanced Normal care but avoid rough handling Kunzite (Spodumene) Occasionally heated and/or irradiated to enhance color Avoid sudden temperature changes, rough handling and exposure to strong light. Kyanite Not routinely enhanced Avoid rough handling, steam and ultrasonic cleaning Labradorite Not routinely enhanced Avoid rough handling, steam and ultrasonic cleaning Lapis Lazulli Routinely dyed, wax or resin impregnated to improve color and luster Avoid chemicals, steam and ultrasonic cleaning Lepidolite Not routinely enhanced Normal care Malachite Occasionally dyed, wax or resin impregnated to improve color uniformity and surface appearance Avoid chemicals, steam and ultrasonic cleaning Mariposite Not routinely enhanced Normal care Moldavite Not routinely enhanced Normal care Moonstone Not routinely enhanced Normal care Morganite (Beryl) Routinely heated and/or irradiated to enhance color Normal care Mother of Pearl Routinely dyed to produce a wide variety of colors Avoid chemicals, steam and ultrasonic cleaning Muscovite Not routinely enhanced Normal care Onyx (Chalcedony) Black Onyx Routinely heat-treated, irradiated, bleached and dyed to induce different colors Always dyed Normal care Opal Occasionally oil, wax or resin treated to hide cracks and provide stability. “Matrix” variety commonly treated with sugar and acid depositing carbon in pore spaces significantly darkening the stone Avoid chemicals, steam and ultrasonic cleaning Pearl Routinely bleached, dyed and/or irradiated to improve or induce color Avoid chemicals (including hairspray and cosmetics), steam and ultrasonic cleaning Peridot Not routinely enhanced Avoid chemicals, steam and ultrasonic cleaning, sudden temperature changes Petalite Not routinely enhanced Avoid rough handling, ultrasonic cleaning Petrified Wood (see Chalcedony) Occasionally bleached and heated to improve color Normal care Pietersite Not routinely enhanced Normal care Pyrope (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Rainbow Calsilica An artificial material created for carving/lapidary purposes. Avoid chemicals, steam and ultrasonic cleaning Rhodochrosite Not routinely enhanced Avoid chemicals, rough handling, and excessive heat. Rhodolite (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Rhodonite Occasionally dyed to even color Normal care Rosenite™ (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Rubellite (Tourmaline) Routinely heated and/or irradiated to improve color Normal care but avoid sudden temperature changes Ruby Routinely heated to improve color and/or clarity. Occasionally diffusion heat treated with chemicals to improve color. Often clarity enhanced with borax and/or lead glass to fill fissures and fractures. Occasionally enhanced by a combination of these treatments. Normal care Rutilated Quartz Not routinely enhanced Normal care Sapphire Routinely heated to improve color and/or clarity. Occasionally diffusion heat treated with chemicals to improve color. Occasionally clarity enhanced with borax and/or lead glass to fill fissures and fractures, and occasionally enhanced by a combination of these treatments. Normal care Scapolite Routinely irradiated for color enhancement Avoid steam and ultrasonic cleaning, avoid exposure to strong light Serpentine Routinely dyed and/or impregnated with waxe to improve appearance and enhance colors Avoid steam and ultrasonic cleaning Shell Commonly dyed to produce a wide variety of colors Avoid chemicals, steam and ultrasonic cleaning Smokey Quartz Routinely heat-treated or irradiated to improve color Normal care Sodalite Not routinely enhanced Avoid chemicals, steam and ultrasonic cleaning Spessartite (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Sphene Not routinely enhanced Avoid chemicals, sudden temperature changes, and rough handling Spinel Not routinely enhanced Normal care Sugilite Not routinely enhanced Avoid steam and ultrasonic cleaning Sunstone Not routinely enhanced Avoid chemicals, steam and ultrasonic cleaning Tanzanite Routinely heated to remove brown tones and purify , violet- or violet colors Avoid steam, ultrasonic cleaning and sudden temperature changes Tiger Iron Not routinely enhanced Normal care Tiger's Eye (Quartz) Routinely heat-treated, dyed or bleached to enhance color Avoid sudden temperatures changes and strong chemicals Topaz (other than ) Routinely heated to enhance colors Normal care but avoid sudden temperature changes Tourmaline Greens and s routinely heat-treated to enhance color. Normal care but avoid sudden temperature changes Tsavorite (Garnet) Not routinely enhanced Normal care but avoid sudden temperature changes Turquoise Routinely stabilized (impregnated) with plastic or resins to enhance durability and color, and occasionally dyed Avoid chemicals, steam and ultrasonic cleaning. Perspiration and cosmetics may alter color. Unakite Not routinely enhanced Avoid chemicals, steam and ultrasonic cleaning Variscite Occasionally stabilized (impregnated) with plastic or resins to enhance durability and color, and occasionally dyed Avoid chemicals, steam and ultrasonic cleaning Verdelite (Tourmaline) Routinely heated to improve color Normal care but avoid sudden temperature changes White Aqua™ (Beryl) Routinely heated to remove faint color Normal care Yellow Beryl (Heliodor) Routinely heated and/or irradiated to improve color Normal care but avoid excessive heat Zircon Routinely heat-treated to induce color and improve yellows and reds Avoid abrasives, rough wear and exposure to strong light.

Various Other Treatments:

• Bleaching: Use of chemicals to lighten or remove a gem's color.
  
• Coating: Use of surface treatments such as films, lacquers, etc. to provide color or other special effects.
  
• Dyeing: The introduction of coloring matter into a gem to give it a new color or greater intensity.
  
• Filling: Introduction of colorless borax, lead glass or other substances into cracks through heating.
  
• Gamma/Electron Radiation: The use of gamma or electron irradiation for the purpose of changing a gem's color, may be followed by a heating process to stabilize the color. Such stones do not exhibit residual radioactivity.
  
• Heating: The use of heat to clarify, change color or create phenomena in gems.
  
• Infilling: The intentional filling of surface breaking cracks and cavities with a foreign material such as synthetic resins with hardeners (Opticon), glass or plastic.
  
• Lasering: The use of a laser to drill into a stone and remove or alter an inclusion, refers most often to diamonds.
  
• Oiling or Resin Infusion: The intentional filling of surface breaking cavities and cracks in transparent or translucent gems with a colorless oil, wax, resin or man-made unhardened resin.
  
• Irradiation: The use of neutron bombardment to alter color. This process creates residual radioactivity and such stones must receive a Nuclear Regulatory Commission safety release prior to sale. Usually used in combination with other radiation and or heating treatments.
  
• Bonding: The intentional use of a colorless bonding agent (usually plastic) within a porous gemstone.
  
• Diffusion: The use of specific chemicals during a high temperature heating process for the purpose of penetrating the surface layer (usually to a slight depth only) with coloring or star-making chemicals.
  
• Waxing/Oiling: The impregnation of colorless wax, oil or paraffin into porous opaque gems to improve appearance.
  
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