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Gemstone Enhancements

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Gemstone Enhancements
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  Introduction: What are enhancements?
Types of Gemstone Enhancements
A list of Gemstones and Their Common

Most gemstone material, both cut stones and often rough, is enhanced. For most gemstones, the enhancements have relatively no effect on value, are permanent, and undetectable to the human eye (and often difficult to determine under a microscope as well). Enhancements increase the available supply of gemstones, thereby increasing their affordability as well. Giving Mother Nature a little hand has produced some wonderful results that imitate some of the natural processes that accompany geologic formation (such as heat and irradiation) of gemstones.

What are enhancements?    

Gem enhancements, or treatments, are human initiated processes that improve the appearance and/or durability of a gemstone. Heat treatment, using high temperature to change the appearance of color of a gem, is one of the oldest and most common enhancement processes; it has been used for millennia.

As a gemologist, I assume that most gems are treated, and I encourage my clients to understand this without losing their love for gems and jewelry. Where gem enhancement makes the largest difference is in disclosure. Buyers have a right to know about and understand gemstone enhancements.

The Federal Trade Commission (FTC) has strict guidelines concerning the disclosure of gemstone enhancements. Recently, the jewelry industry has been working with the FTC to tighten the legal guidelines for disclosure of gemstone treatments. Disclosure means that a buyer has the right to know which enhancement processes have been performed on a gemstone.

For simplicity's sake, I have compiled a list of the different categories of enhancements and the gemstones commonly treated with this process. Most of these enhancements are commonly accepted within the gemstone trade as routine processes. Unless otherwise stated as a natural, untreated gemstone, the gem materials I have used in my designs, like most gemstones, have been enhanced in some way.

One final note:
In the case of rubies and sapphires, however, there is a price difference between a natural, untreated stone and a natural, treated stone. Before paying the premium for an untreated ruby or sapphire, one must be certain that the gemstone is, in fact, untreated. The determination of treated vs. untreated can be determined fairly easily with equipment in a gemological laboratory such as the Gemological Institute of America (GIA) in California or the Gubelin Laboratories in Switzerland.


Gemstone Enhancements    


Heat treatments are used to lighten, darken, deepen, or even completely change gemstone color. The temperatures and length of time vary, but temperatures range from 157-1900 C. Heat treatment works like it sounds- the stones are heated.

Irradiation affects only a gemstone's color. Subatomic particles, such as gamma rays, are used to bombard the electrons of the gem, causing them to be 'knocked' lose, and captured by other atoms. The light-absorbing pattern is thereby changed and as a result, so is the color. In the case of gamma rays, no leftover radioactivity remains. Many gem laboratories regularly check irradiated gemstones to ensure that they are not radioactive.

This is the largest group of enhancements with the greatest number of effects on the gemstones. These include:

Bleaching and Dyeing
Just like they sound: chemicals are used (such as bleach and hydrogen peroxide) to remove color; just the reverse, dyeing adds a chemical agent to change or deepen color. Dyeing works best with porous materials such as lapis lazuli.

Chemical agents are used in the presence of heat. The chemical agents penetrate a shallow layer of the surface, become part of the crystal structure, and change color superficially. Sapphires and rubies can be diffusion treated.

Oiling & Impregnation
This enhancement involves the filling of surface reaching fractures with oil (for oiling) or a plastic polymer substance (for impregnation) to make them appear less noticeable. Emeralds are routinely oiled and jadeite is commonly polymer impregnated.



A List of Gemstones and Their Common Enhancements

can be dyed

Amethyst: Not always treated. If treated, heat treatment can lighten the color. Can also be produced by irradiating citrine to turn it from yellow to purple.

Aquamarine: heat treatment can change green material to blue.

Carnelian: can occasionally be dyed; heat treatment can improve color.

Citrine: Not always treated. If treated, can be produced by heat treating amethyst to change color from purple to yellow.

Diamond: Colorless diamonds are generally untreated. However, they can be laser drilled, the impurities bleached, and then fracture filled to improve clarity. Light yellow and brown diamonds can be irradiated to change color to green, brown, blue, yellow, orange, and more rarely, pinks and reds.

Diopside: no known treatments.

Emerald: Traditionally, for hundreds of years, almost all emeralds have been treated by soaking in oil to improve appearance. The oil penetrates the surface reaching fractures and makes them appear less noticeable. It can also help to increase color saturation. Today, while still routine, this practice has taken on a more advanced level. Instead of oil, emeralds are commonly treated with a high-grade epoxy resin, such as Opticon (registered), to improve their appearance and increase durability. The 5.76 carat emerald featured on the "Green with Envy" page has been treated in this more advanced fashion. These treatments are not permanent and can all be reversed. Because it is well known that all emeralds are treated, this has virtually no effect on value.

Garnet: no known treatments.

Iolite: no known treatments.

Jade (both jadeite and nephrite): can be bleached, dyed, polymer impregnated, or heat treated- or a combination of these. The trade typically refers to three types of jadeite: 'A' jade, 'B' jade, and 'C' jade.

'C' jade is the most common type of jade and accounts for most jade found in jewelry. It is usually bleached, dyed, and polymer impregnated.

'B' jade is a natural color jade that has been bleached to remove any dark, unattractive discolored areas. It is also often polymer impregnated (which increases the durability of this already tough gem material).

'A' Jade is completely untreated in every way and is both very rare and expensive.

Kunzite: can be (but very uncommonly) irradiated
Kunzite Note: Unrelated to enhancement--Exposure to intense sunlight over a very long period can cause the gradual fading of this pink gem.

Lapis: commonly dyed and polymer impregnated or oiled to improve color and luster.

Malachite: very uncommonly impregnated with a polymer/epoxy resin.

Moonstone: no known treatments.

Opal: I use untreated opals and occasionally opal doublets. Opal doublets are an assembled stone that combines, via epoxy, a thin layer of opal backed by either chalcedony or boulder rock.

Pearl: Routinely bleached to remove discoloration. White pearls are dyed to achieve a pink overtone (rose overtone). While some pearls are dyed to change color completely, most dark colored Chinese pearls are irradiated to change their color. The pastel colors of Chinese freshwater pearls are supposedly untreated and therefore of natural color.
Pearl note: Mabe pearl: Mabe pearls are cultured 'blister pearls.' In the culturing process, instead of inserting a bead nucleus 'free-floating' into a mollusk or oyster to get a round-shaped pearl, the nucleus is attached to the inner lining of the shell. The mollusk then begins to 'cover' this irritant with calcium carbonate, composed of calcite and aragonite, the two minerals that make up the pearly nacre of a pearl. When the mollusk is harvested, the pearl that has formed like a blister on the inner shell is cut out and backed with mother of pearl or shell.
Pearl note: Keshi pearls: Keshi pearls are entirely untreated. After being removed from the mollusks, they are washed only with a gentle soap and rinsed with water.

Peridot: no known treatments.

Rock Crystal Quartz: no known treatments.

Ruby: can be heat treated, diffusion-treated (I do not sell), and occasionally oiled and dyed (I do not sell).

Blue sapphire--can be heat-treated or diffusion treated (I do not sell)
Yellow/Orange Sapphire--irradiated.

Smoky Quartz: usually natural; very black material is usually irradiated.

Tanzanite: routinely heat-treated.

Blue: irradiated followed by heat treatment.
Pink: heat-treated.

Pinks & Reds: commonly irradiated.
Greens: often heat-treated.

Turquoise: can be polymer impregnated
Note: Turquoise is often reconstituted, and this can be hard to detect. Reconstituted turquoise involves grinding up pieces of turquoise, pressing them into solid pieces with an adhesive binder such as an epoxy, and then recutting.

*Important note to gemstone enhancements: While the following list describes many of the changes to various gemstones, gemstone enhancement is not an exact science. Results of treatments are not always predictable. For example, two gemstones of the same color from the same geographic location and deposit, when heat-treated, may turn completely different colors.