Thursday, July 18, 2013

More on Gemstone Treatments

Dyed Chalcedony
Since I am interested in knowing how and why gemstones are treated, I thought you might like to know to.  

Many dealers treat gemstone materials through several of the methods listed below.  The reason being, to gain higher prices when selling on the world markets.

The goal of any gem treatment is to improve the stone's color and clarity. Some methods help to remove inclusions; some fill the cracks in a stone; other methods can make clear crystals appear colorful.

The following list will help you identify and understand some of the gemstone treatments known to exist in the gem trade. Some of these treatments are temporary, while others are permanent.

Heating : Heat is used to achieve a desired alteration of color, clarity, and /or phenomena. This is a permanent treatment. Examples: Tanzanite, Blue Topaz, Smoky Quartz, Citrine, Aquamarine, Quartz.

Diffusion: The use of chemicals in conjunction with high temperatures to produce color and/or asterism-producing inclusions. This is a permanent treatment. Examples: Topaz, Sapphire.

Irradiation : The use of neutron bombardment to alter a gemstone's color; may be followed by a heating process. This is a permanent treatment. Examples: Topaz, Smoky Quartz, Diamonds.

Coating : The use of surface enhancements such as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color or add other special effects. This is a temporary enhancement.Examples: Emerald, Opal.

Dyeing : The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.  Sometimes stable, but often not, may fade or bleed. This is a temporary enhancement. Examples: Chalcedony, Quartz, Agate.  Sometimes (not always) also used to intensify the color of Amethyst, Garnet, Iolite and many other stones.

Dyed Pink Chalcedony
Oiling/Resin Infusion : The intentional filling of surface breaking cavities with a colorless oil, wax, natural resin, or unhardened man-made material into fissured transparent gemstones to improve appearance. (i.e., oil, man-made resin, cedar wood oil, Canada balsam, paraffin, etc.) This is a temporary enhancement. Examples: Emerald.

Filling : As a by-product of heat enhancement, the presence of solidified borax or similar colorless substances. This is a temporary enhancement. Examples: Emerald, Opal.

Infilling : The intentional filling of surface cracks or fractures usually with glass, plastic, or other hardened foreign substances to improve durability, appearance and / or weight. This is a temporary enhancement. Example: Emerald, Mexican Opal.

Waxing/Oiling : The impregnation of a colorless wax, paraffin and oil in porous opaque gemstones to improve appearance. This is a temporary enhancement. Examples: Emerald, Opal.

Laser : The use of a laser and chemicals to reach and alter inclusions in diamonds. This is a permanent treatment.

Vacumn Deposition  : A newly patented process, that deposits a permanent coating. Stable. This is how all "Mystic Topaz", Green Topaz, and most or probably all Pink Topaz available to the average consumer is acquirred.

Stabilization The use of resin like coatings. Usually stable, but may attract grime and discolor. Common with Turquoise.  Sometimes a dealer may incorrectly use this term for chips that have been reconstituted and dyed.

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