Agate: see Chalcedony

Alexandrite is not known to be enhanced by treatment.

Amber is occasionally heated to improve appearance, to add “sun spangles,” and to deepen the color. It can be dyed or surface treated to add color. Treatment stability: good.

Amethyst may be heated to lighten its color. Treatment stability: excellent.

Ametrine was discovered in Bolivia in the late 1970’s. It occurs naturally and exhibits both the purple of amethyst and the yellow of citrine within the same crystal. Occasionally it can be heat treated to improve the color. Treatment stability: excellent.

Aquamarine is commonly heat treated to remove the greenish hues and to enhance the blue. Treatment stability: excellent.

Blue beryl is always irradiated to obtain its color. Treatment stability: poor.

Pink beryl is occasionally heat treated to obtain its color: Treatment stability: excellent.

Yellow-green and red beryl are not known to be enhanced by treatment.

Yellow beryl is commonly produced by irradiation. Treatment stability: good.

Carnelian is commonly heated to produce its color. Treatment stability: excellent.

Chalcedony: agate, black, banded, blue, and green are usually dyed to enhance their colors. Treatment stability: excellent.

Chrysoprase is not known to be enhanced by treatment.

Chrysoberyl: yellow, brown, and green and cat’s eye chrysoberyl are not known to be enhanced.

Citrine is commonly produced by heating various types of quartz-family stones, especially the brownish varieties. Unless otherwise noted, we assume that all the citrine we sell has been heat treated. Treatment stability: excellent.

Coral is an organic gem, not a mineral. Enhancements include bleaching and stabilizing with colorless wax or plastic. Treatment stability: excellent. Coral may also by dyed. Treatment stability: good.

We do not sell treated diamonds, and the Canadian diamonds we sell come with documentation as to their untreated origin. When diamonds are treated, they may be heated, subjected to high pressure and high heat (HPHT), or irradiated to enhance their color. They may be laser-treated to improve appearance. We sell only untreated diamonds.

Emeralds, over the centuries, have been treated with oils and waxes to purify their transparency. Today, various types of resins are also used to penetrate the open fissures on the surface of the stones. Unless otherwise noted, we assume that all the emeralds we sell have been treated in some way. Treatment stability: Fair to Good.

Garnets are not known to be enhanced by treatment.

Iolite is not known to be enhanced by treatment.

“A” Jade is natural, untreated jadeite jade. It is commonly polished and waxed to fill the stone’s natural and microscopic surface pores. Treatment stability: very good. There are three other types of Jade which we do not sell: “B” is bleached, polymer-impregnated jadeite jade. “C” jade is dyed jade; and “D” is bleached, dyed, polymer-impregnated jadeite jade. We sell only “A” jade.

Jasper is not known to be enhanced by treatment.

Lapis Lazuli is occasionally impregnated with wax or oil and can be dyed to improve color and uniformity. Un less otherwise noted, we assume that the lapis we sell may have been waxed or dyed. Treatment stability: good to fair.

Moonstone is not known to be enhanced by treatment.

We do not sell treated opal. Opal, white opal, crystal or water opal and black opal are rarely enhanced other than by cutting. When they are enhanced, they may be immersed in sugar and sulfuric acid which brings out the fire, and they may be permeated with colorless oil, wax, resin, plastic and/or hardeners which can improve the opal’s durability. Fire opal (red or orange) is almost never enhanced.

Opal doublets are created by bonding a layer of opal to a bottom layer of black jade or other mineral to improve the durability and color of the opal. The opal doublets we sell are not treated in any other way.

White Japanese Akoya cultured pearls may be bleached to lighten and improve their color. Akoya pearls come in a variety of natural colors. Akoya pearls can be dyed or irradiated to produce a wide range of colors. Fresh water cultured pearls can be enhanced in the same manner. Unless otherwise indicated, we assume that the pearls we sell may have been enhanced.

Mabe Pearls are grown against the oyster’s shell using a hemispheric insert instead of a round one. When formed, the pearl is cut out of the shell. The insert is removed and replaced with resin and backed with a piece of mother of pearl. Mabe cultured pearls may be bleached to lighten and improve their color. Mabe pearls come in a variety of natural colors, but mabe pearls can be dyed or irradiated to produce a wide range of colors. Unless otherwise indicated, we assume that the mabe pearls we sell may have been enhanced.

Peridot is not known to be enhanced by treatment.

Rubies are commonly heat treated to maximize purity and intensity of the red color. Treatment stability: excellent. We do sell untreated rubies upon request.

Sapphires are commonly treated with heat to improve color and clarity. Treatment stability: excellent. We do sell untreated sapphires upon request.

Sodalite is very rarely enhanced.

Tanzanite must be heated to permanently change its color from orange-brown to violet-blue. Treatment stability: excellent.

Blue topaz is irradiated and heat treated. We assume that all the blue topaz that we sell is treated. Treatment stability: excellent.

Yellow/Orange topaz is occasionally irradiated to intensify its color. Treatment stability: variable.

Pink Topaz is usually heated and may be irradiated to improve its color. Treatment stability: very good to excellent.

Tourmalines are occasionally heated or irradiated to improve their colors. Occasionally, surface-breaking fissures may be filled with resins. Treatment stability: very good to excellent.

Turquoise is commonly permeated with plastic or colorless oil or wax to improve its color and durability. Treatment stability: good. Occasionally turquoise is dyed to improve its color, but this is an unstable enhancement.

Blue zircon is heat treated to achieve its color. Treatment stability: good.