Gem Stone Enhancement

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s a consumer, you will regularly encounter in the marketplace gems that have been treated to change their appearance. Next thing comes up to the mind whether a particular gemstone is or isn’t treated. However, gems can often be treated in ways meant to alter their color or clarity. In addition to enhancing their appearance, the process may also improve (or in some cases diminish) the gem’s durability. Because these treatments are not always apparent to the unpracticed eye, and are sometimes difficult to distinguish even by experts, it is necessary and legally required for anyone selling a gem (including consumer to consumer trade) to disclose the treatment procedure it may have received.

Non-disclosure of this treatment could cause a person to believe that a particular gemstone was of higher quality naturally and therefore be more valuable than it actually is. An added challenge is that treatments can be permanent, long lasting, or short-lived under normal jewelry use. The following glossary includes terms that are often used in the gem treatment nomenclature. Finally, treatments for gemstones are constantly being changed and refined, and the detection of these new treated gems is an important.

As a company policy Ceylon Natural Gems Always disclosed the treatments done to the gem stones. Majority of our stones we were selling Natural Untreated. As a treated material we are selling only two kinds of gem materials which are heated and irradiated stones. These two treatments accept under any circumstances in the gem and Jewelry trade.

The following guide will give a short description of the treatment process, some gems for which the process is used, how easy or difficult the treatment is to detect for a trained gemologist, how often the treated gem might be encountered in the jewelry trade, and how durable the material is to normal handling procedures. Any special care instructions for these treated gems are also provided.

Bleaching

Bleaching is a process for organic gem materials such as ivery,coral and for pearls and cultured pearls. It lightens the color and is permanent and undetectable. No price difference exists as a result.

Jadeite is often bleached with acid to remove an unwanted brown component from the material. Bleaching in jade is typically part of a two-step process: because acid bleaching causes the material to become slightly porous or susceptible to breakage along fractures, it is then subsequently treated with polymer impregnation to fill these open spaces to produce a better overall appearance.

All types of pearls are routinely bleached with hydrogen peroxide to lighten and improve their uniformity of color.

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. The company is now coating topaz in all colors, including pinks and rich "imperial" tones. Recent reports have indicated that tanzanite is showing up in the labs with coatings on the pavilions to improve the appearance of saturation. Coatings are occasionally identified on diamonds to improve the apparent color of an off-colored stone and deceive a buyer.

Some black coral (also known as Horn coral) has been reported as bleached and then coated with relatively thick layers of artificial resin with the goal of protecting the coral and intensifying its color.

Thin-film coatings are sometimes used on diamonds to change their color. Crude, yet effective coatings can also include the use of permanent ink markers along the girdle surface of a diamond, causing its face–up appearance to be affected by the color of the ink used. More modern coating methods use metal oxide thin films.

Some pearls reportedly have been treated with a colorless hard coating in an effort to improve durability.

Occasionally, quartz is coated with metal oxides to create colors rarely seen in natural quartz.

Though rarely used, tanzanites have been coated to improve the intensity of their blue-violet color.

Some colorless topaz is coated with metal oxides to create the appearance of a variety of different colors. In the past, such treatments were often described as a form of “diffusion” of a chemical into the surface of the gemstone, but this was a misnomer since in most cases the added color was confined to the surface of the gemstone.

Dying

Introducing colored dyes into porous or fractured gems to change their color. Such fractures are sometimes purposely induced by heating the gem so that an otherwise non-porous material can more readily accept the dye.The process has been used since ancient times for materials such as coral, turquoise, lapis lazuli, howlite, nephrite jade, chalcedony, quartz, emerald, and ruby.

Dye often improves the appearance of lower–quality natural and cultured pearls by enhancing their color.

Fracture or Cavity Filling

Filling surface-reaching fractures or cavities with a glass, resin, wax or oil to conceal their visibility and to improve the apparent clarity of gem materials, appearance, stability, or in extreme cases—to add to a slight amount of weight to a gem. The filling materials vary from being solids (a glass) to liquids (oils), and in most cases, they are colorless (colored filler materials could be classified as dyes).

Surface-reaching fractures are sometimes filled with high-lead-content glass. This reduces the visibility of the fracture, with the goal of enhancing the appearance of the diamond. The filled fracture is still present – it is just less apparent.

Surface-reaching fractures in emerald are sometimes filled with essential oils, other oils, waxes, and “artificial resins” —epoxy prepolymers, other prepolymers (including UV-setting adhesives), and polymers to reduce the visibility of the fractures and improve the apparent clarity. These substances have varying degrees of stability in treated emeralds, and the volume of filler material present can range from insignificant to major amounts.

Numerous surface-reaching fractures are filled with a glass to lessen their visibility and make the gem more transparent than it really is. In some cases, the amount of filler glass can be significant in a treated ruby.

Heat Treatment

Heating is the most common treatment available. It can cause the color of a stone to lighten, darken, or change completely. It can bring about an improvement in clarity and brightness. Heating is detectable only by trained observers in a laboratory setting and is usually irreversible under normal conditions. Unheated rubies and sapphires will contain microscopic rutile needles or tiny gas bubbles in pockets of liquid which are evidence that laboratories can use to guarantee that these stones have not been heated. If these gems are the finest color they will command premium prices due to their extreme rarity.

Within the last couple of decades, it was discovered, quite accidentally, that if sapphires were heated along with a flux containing beryllium, the color of the sapphire could be dramatically changed.

When amber is submerged in hot oil—linseed oil for example—it's inherent body color can darken, and the material can take on a clearer appearance. The hot oil can also cause the material to develop a series of spangled, glittery inclusions.

Heating can remove unwanted brownish inclusions in some amethysts or lighten the color of overly dark stones.All purple and blue varieties of the stone are the result of heat treatment. The stone is a yellowish-brown "bug juice" color when it is mined, but when heated to between 800-900 degrees Fahrenheit, it becomes that gorgeous violet blue that is used in jewelry. The stone has never been found in another locality, so it is indeed a depleting resource. It is somewhat soft (6-7 on Moh's scale of hardness), and has a direction of cleavage, along which it can be easily broken. It is desirable because of its' elegant and opulent color.

Without treatment, much of the aquamarine is blue–green in coloration. Heating in a controlled environment can remove the greenish color component from the material to produce a more blue appearance.

Citrine is a yellow or golden variety of quartz. Most citrine available today is heat-treated amethyst. When amethyst is heated to about 900 degrees Fahrenheit, it alters to to a golden tone. Citrine has been credited with curing urinary tract infections, jaundice and kidney ailments. This is obviously a color association. I prefer the chakra based interpretation that views citrine as uplifting, bright, energizing and inspirational.

Heating can remove purplish coloration rendering a more pure red color. The process can also remove “silk” (minute needle–like inclusions) that can cause a gem to appear lighter in tone and be more opaque. Heating can also cause recrystallization of the silk inclusions to make them more prominent which allows the gemstone to have stronger asterism (a reflecting star effect).

Heating can intensify, or even induce, a blue coloration in sapphires. The heating can also remove “silk” inclusions, which also helps to make the material appear more transparent. It in can also cause recrystallization of the silk inclusions to make them more prominent, which allows the gemstone to have stronger asterism (a reflecting star effect).

The mineral zoisite, which includes the gem variety known as tanzanite, it is often heated at low temperatures to remove a brownish color component to produce a stronger purplish-blue color.

Heating yellowish pink topaz sometimes has the effect of removing the yellowish color component, thereby intensifying the pink color. Heating is also used to control the color of blue topaz—the material that may have started out as colorless is irradiated followed by heating which results in a desirable blue color.

Sometimes heat treating can cause overly dark green material to become lighter in tone, or it may affect the color in other tourmalines.

Some reddish brown zircons are heated in controlled environments to produce more commercially viable colors, including an intense blue.

Impregnation

the surface of a porous gemstone is permeated with a polymer, wax or plastic to give it greater durability and improve its appearance.The most commonly encountered wax or plastic impregnated gemstones are opaque, and they include turquoise, lapis lazuli, jadeite, nephrite, amazonite, rhodochrosite and serpentine.

Irradiation

Exposure of a gem to an artificial source of radiation to change its color. This is sometimes followed by a heat treatment to further modify the color. This second step also known as a “combination treatment.

Some bright orange colors are induced in sapphires with a pale yellow natural color. The color in these is not stable and fades upon exposure to light.

Neutron and electron radiation are the most common forms of artificial irradiation, and it is possible to induce black, green, blue green, deep yellow, orange, pink and red diamonds (often combined with a secondary step of heating, to achieve certain colors).

Some pearls are irradiated resulting in dark gray colors.

Varieties of quartz may be irradiated to produce amethyst, and some combination treatments that include heating after irradiation resulted in green quartz.

Colorless topaz has little commercial value in the gem market today, but it can be subjected to artificial radiation to dramatically change its color. Used in conjunction with heat treatment, a variety of strong blue colors can be achieved for topaz.

Lattice Diffusion

Chemicals, like beryllium, were infused at high temperatures, and actually penetrated the gems. Early diffusion only produced color on the surface of the gem's surface and was referred to as "Surface Diffusion". Surface diffusion was easily detectable with immersion, and often with simple magnification. Great advancements have been made in diffusion treatment in the last decade and it was discovered that if corundum is heated to very high temperatures for a long duration, the diffusion would penetrate the entire stone! It can improve color, change color, or create asterism (stars).

Within the last couple of decades, it was discovered, quite accidentally, that if sapphires were heated along with a flux containing beryllium, the color of the sapphire could be dramatically changed.

while experimentation during the 1980s concentrated on diffusion of titanium and chromium (which are coloring agents in corundum), the ability to fully penetrate the stone with color met with little success. In 2003, very strongly colored sapphires began to appear in the market, and diffusion was again suspected. It was found that it was diffusion — but of a new element: beryllium. Beryllium which has a much smaller atom than titanium or chromium, was able to diffuse all the way through a sapphire; even large sapphires, successfully changing their color. It was soon found that the color of rubies could be accentuated as well using this treatment process.

Varieties of feldspar, notably andesine and labradorite were found to be receptive to the diffusion of copper, completely altering their color.

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