Thursday, April 16, 2009

Jewelry - All About Enhancements and Treatments

Ever wonder how that piece of Turquoise in your ring got to be shaped so perfectly? Or why, despite all the matrix (those spiderweby lines throughout the stone), the stone isn't crumbling? My blog article today will help explain how and why turquoise and so many other gemstones have such a beautiful appearance. It's not just luck, or even an incredible job on the part of the lapidary!

Life has been crazy-busy lately, but I wanted to take some time to post some information about gemstone enhancements and treatments.

First of all, treatments and enhancements have nothing to do with whether or not a gem is a lab created gemstone or a synthetic gemstone. In fact, the terms really only apply to genuine gemstones. Gemstone treatment and enhancement has been practiced for literally thousands of years. The oldest known reference to it is in a document authored by Pliny the Elder, a Roman author and naturalist who died in the famous eruption of Mt Vesuvius which destroyed the city of Pompeii in AD 79. Some of those same treatments and enhancements are still in use today!

While some enhancements can barely be detected, other treatments like heat treating and irradiation produce dramatic and beautiful changes. One example is the transformation of colorless topaz into beautiful blue topaz thru this process. Some gemstones, like yellow citrine, tanzanite and pink topaz would not be available at affordable prices if it wasn't for these treatments. In an ironic twist, natural gemstones that have not been treated, like unheated rubies and sapphires, have become much more expensive recently - not because they are more naturally beautiful, because they usually aren't, but because it is so rare to find an untreated ruby or sapphire.

So... let's look at some of these treatments and enhancements.

Heating - the most commonly used treatment, subjecting a stone to heating can dramatically changes the stone's natural color to make it lighter, darker, or completely different. A heated gemstone can only be detected by a trained observer in a lab. Some of the gemstones that are routinely heat treated are: zircons, citrine, rubies, sapphires, tanzanite, aquamarine, and pink topaz. Rubies that are treated with heat often develop tiny surface fissures which have to be subsequently treated with flux healing (the filling of a fracture with molten glass which bonds permanently with the stone).

Dyeing - many of the gemstones available today, especially some of the newer cultured pearls, and onyx, chalcedony, and agate are routinely dyed. The dyes applied to these stones are very prevalent, very permanent and well received in the jewelry trade. Other gemstones that may frequently be dyed to enhance their appearance are jade, lapis, emeralds, rubies, turquoise, sapphires and coral. Caution should be used since sometimes, dyeing is used to disguise poor quality rather than to change or enhance colors.

Impregnation and Stabilization - Impregnation is the infusion of paraffin or was into a porous material. Stabilization is the introduction of a bonding agent into a porous material and is the most permanent of these two methods. The most commonly used stabilizing agent is plastic. Turquoise is commonly stabilized, allowing it to retain its original color and luster. Opals may also be stabilized, but it is usually done to make a lower quality stone appear more beautiful.

Irradiation - Irradiation is the process of pounding a material with radiation. It is sometimes followed by heating to produce dramatic color changes. Naturally off colored diamonds can be irradiated and then heat treated to produce intense colored diamonds in bright blues, yellows, pinks, browns and greens. Blue Topaz is probably the most commonly irradiated gem, although quartz and tourmaline are also frequently irradiated. In the US, irradiation is regulated by the Nuclear Regulatory Agency to ensure the gemstone's safety after treatment, but this protection is not guaranteed on gemstones bought from outside the US.

Coating - This process involves the application of a lacquer or film to a gemstone to improve its appearance. Topaz is routinely coated, and tanzanite and opals are sometimes coated to improve their appearance and/or intensify their color.

Filling/Infilling - Liquified glass, plastic or other materials are applied to gemstones with surface fractures or small cavities to correct these imperfections. This type of treatment is only detectable under magnification or dark-field illumination. Rubies, tourmaline, and diamonds are sometimes filled to enhance their appearance.

Bleaching - Organic gem material like coral, ivory, pearls and bone can be bleached through a chemical process to lighten their color. This is a permanent and completely undetectable treatment.

Oiling - This process involves colorless oil being pressurized into the surface fissures of a gemstone. Emeralds are routinely oiled. Any stone that has been oiled may need to be re-oiled if it is cleaned using ultrasound or steam.

Lasering - Used primarily with diamonds, lasering involves drilling tiny holes into the stones to reach inclusions or flaws in the stone. The inclusion is then vaporized or bleached if it was not already corrected by the lasering.

Composite Assembly - Assembled stones may be composites like doublets and triplets, or they may be foilbacks. A composite stone is two or three pieces of material fused or joined by colorless cement. Although any stone may be made into a composite, opals are the best-known. An opal triplet consists of a piece of good opal sandwiched between a top layer of clear quartz and a bottom layer of low-quality opal. A doublet is usually good opal underneath a quartz layer. The quartz helps protect the delicate opal. Composites also allow the use of gemstones too small to be used otherwise.

Reconstruction/Reconstitution- Crushed, fragmented stone is mixed with a colorless acrylic resin and sometimes dyed to create a larger slab. While this contains genuine gemstone material, it is considered an imitation gemstone. Amber and Turquoise are the most commonly reconstituted gemstones.

Keep in mind that not all gemstones need to be enhanced or treated. Peridot, Iolite, some Tourmaline, Hematite, and Chrysoberyl are examples of gemstones that are more likely to not require any of these processes. It's important to keep in mind that while some treatments and enhancements are acceptable and necessary to produce beautiful gemstones or unique colorations, they can also be used to disguise poor quality stones... although in my opinion, some stones are only enhanced by natural flaws and imperfections. You are the only one who can judge a gemstone's beauty for yourself - in this case, beauty is truly in the eye of the beholder!

1 comment:

kim* said...

lots of cool info thanks

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