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Gemstone Treatements
When buying or selling gemstones, the question of gemstone treatment often arises. The finest, untreated natural gemstones are very rare and are consequently very expensive. The first documentation of gemstone treatment was presented by Pliny the Elder. Some enhancements improve on nature, cannot be detected and are permanent, thus providing the gem market with a larger supply of beautiful gemstones. Virtually every colored gemstone cut into beads or cut for setting into jewelry on the market today has been enhanced by some method.Gemstones are generally treated to improve or alter color and enhance clarity. Beadworks prides itself of selling top quality gemstone beads and we clearly label any known treatment
used on the gemstones we sell.
The following important product knowledge is offered to help educate you about the common and acceptalbe types of gemstone treatments encountered in the marketplace today.
- Heat Treatment
Heat treating gemstones is the most common and oldest form of enhancement. It is permenant and irreversible. It is considered a "natural" type of treatment since the process is similar to what occured in nature when the stone was formed. The stone is heated to a very high temperature (450 to 1850 centigrade) for 2 to 12 hours. This causes inclusions to dissolve and the chemical elements of the stone to rearrange, thus altering the color and clarity of the stone. The color change may be lighter, darker or completely different.
For example, Tanzanite is brown when mined and only turns the distinctive violet-purple color after heating. Another example is ruby. Only the most valuable and expensive rubies possessing the richest colors are not heat-treated.Heat treated ruby is heated, almost to the melting point which allows the aluminium oxide in the stone to re-form, creating a new crystal stucture. This allows the chromium in the stone to combine with different atoms, allowing for an improved color of red.
Heat treatment is hard to detect, and is considered an acceptable form of enhancement. This allows more stone material to reach the market at affordable prices and it is just as true of gems set in Tiffany rings as it is with faceted rondelles sold at Beadworks. Here is a list of some common heat treated stones and how the heat enhances them:
- Amethyst - lightens the color and changes pale amethyst to "yellow" that will be sold as Citrine.
- Aquamarine - removes the greenish undertones and produces a deeper and bluer colored stone, which is generally more appealing in the market.
- Ruby - improves overall color. heat removes iron, dissolves inclusions and fills tiny cracks.
- Sapphire - lightens, intensifies and clarifies the color.
- Tourmaline - lightens darker shades of the green and blue stone.
- Dyeing
Without dyeing there would be no black onyx, as this is not a natural color of chalcedony! Dyeing involves introducing a coloring matter into a gemstone to give it new color, intensify present color or to improve color uniformity. This is a common practice and can often be detected by carefully examining the string the beads are strung on. Dyed beads can lose their color over time or with exposure to the sun or hea. Always store delicate beads in a pouch, jewelry roll or jewlery box.
- Coating
Coating is a process (used and described for over 200 years! where a lacquer or film of some type is applied to improve a gem's appearance. Today, coatings are increasingly utilized to alter and improve the color of gems. Mystic topaz is an example of a coated gem that was conceived by Azotic Coating Technologies.
- Irradiation
Another common method of color enhancement is irradiation. This process involves exposing the stone to electromagnetic or ionizing rays to move electrons to more desirable color-producing locations. This is also considered an acceptable form of color enhancement and is also permenant and irreversible
- Reconstitution
This process involves combining powdered gemstone material with a
coloring agent, to improve the color and an epoxy binder to hold the powdered material together.
This mixture is molded to form large pieces which are then
cut into beads. This is a permenant process.
- Stabilization
Stabilization of gemstone material is done to improve the surface
durability of soft stones. This process is primarily used on turquoise.
A clear layer of liquid acrylic is applied to the surface which seals the stone and helps to protect it from damage.
Some gemstones are not generally enhanced.
These include: Garnets, Peridot, Iolite, Spinel, Tourmaline , Malachite, Hematite, and Feldspar with the probable exception of labradorite. Keep in mind that new technology in gemstone treatment is always changing and improving and many are seriously difficult, if not impossible, to detect. |
