Gem Enhancement


 
Mark Gershburg, CEO, Gemological Science International
(GSI): The American Standard
 
Gem treatment was found in an Egypt goes as far as 1300 BC.  Many of these treatments are still being used today in the gem and jewelry industry.
Gem treatment was also mentioned in The History of the world by Pliny (Space) The Elder (1st Century AD). In the last two books of his work, he describes many different minerals and gemstones. The topic concentrates on the most valuable gemstones, and he criticizes the obsession with luxury products. 
In the earlier period, treatments of gemstones were usually done by the cutter. The lapidary wanted the value of the finished product to be as high as possible. Today, there are facilities that specialize in treatments of both rough and fashioned gems.
 
BUT WHAT IS ENHANCEMENT OR TREATMENT?
 A treatment is a process of artificially altering and improving the appearance and properties of a gemstone in order to make it saleable or/and better quality.
Some enhancements are permanent, while others are unstable and fade, wear away, or alter with time and exposure to environmental factors. Some of them easily detectable while others are very hard or impossible to detect.
Any kind of gem material could be used for enhancement. As a rule the poor quality material used to produce better quality gems. A fine quality gem usually doesn’t require any kind of enhancement.  
 
THE BASIC REQUIREMENTS FOR IDENTIFICATION OF TREATMENT IN A GEM MATERIAL: 
•  General knowledge of various gemstones and treatments
•  Basic gem instruments sufficient for most gem treatment detection
•  Advanced equipment for further examination
•  Skilled gemologist with good observation skills 
•  Experience and scientific thinking
 
WHAT ARE THE TYPES OF TREATMENTS?
• Heating
• Diffusion
• Oiling
• Irradiation
• Dyeing
• Impregnation and stabilization
• Bleaching
• Coating or painting
• Waxing
• Fracture filling in gemstones and diamonds
• Laser drilling
• High pressure high temperature
 
HEATING OR THERMAL ENHANCEMENT: 
The most versatile and widely used treatment for gems is heating. It was documented by Arabs in 12th century. It is most commonly used to lighten, darken, or change the color of the stone completely, depending on the gem and the desired effect on it. Temperatures, periods of heating, presence or absence of oxygen, all these factors vary and depend upon the gemstones or gem materials.
Heat rearranges the atoms in the stone. In some stones it improves clarity and brightness. It is a combination of heat and some of the chemicals such as beryllium, borax, lead, and tantalum, to permanently lighten, darken, or alter a stone's color to make it more visually appealing.

DIFFUSION:
In the last few decades, it has been observed that heating sapphires along with a flux containing chemicals, like beryllium, at high temperatures resulting in infusion, and penetration of the gems by the chemicals. This process changes the color of the sapphire dramatically. These treatments are known as ‘Lattice diffusion’.
Earlier diffusion treatments produced color change on the surface of the gems and therefore were referred to as ‘Surface Diffusion’. It can improve the color, change the color or create asterism (stars). Surface diffusion is easily detectable with immersion, and often with simple magnification.
 
OILING : 
Oiling of emeralds is universal, while most emeralds are oiled not EVERY emerald is. While oiling improves clarity of emerald, the color improves too as a result of the treatment. The colorless oil seeps into the fissures on the surface of the emeralds. Other colored stones such as rubies, alexandrite and other varieties of chrysoberyl and demantoid garnets could be treated with oils to make surfacing inclusions less visible.
 
IRRADIATION: 
A gemstone's color can be altered through the use of radiation such as electrons, gamma rays or neutrons. This is often followed by a heating process. The enhanced color of irradiated gemstones is permanent.
For example colorless or pale color sapphires, diamonds can be irradiated and heated to change color. Cultured pearls can be irradiated to produce gray or blue colors. Gamma ray irradiation is used for this kind of treatment. The gamma ray usually imparts color to the nucleus of a saltwater pearl instead of coloring the nacre, whereas in a freshwater pearl the gamma ray will make the nacre very dark and may also give it a metallic and even iridescent sheen. 
We should also be aware that some gems have been colored by natural radioactivity in the earth's crust.
 
DYEING: 
Dyeing treatment is an act of adding coloring agents so that they fill a colored gemstone to enhance, alter color, intensify existing color or improve color uniformity.
Dyeing is relatively easily accomplished with porous gems and those crystalline gems which aggregates, as well as gemstones with surface reaching fractures.
The dyes can vary greatly from organic or vegetable dyes to chemical salts and natural pigments. 
Dyes will often vary in its degree of penetration from just the surface to deep within a gem. All dyed gems require special care, for example re-polishing is not recommended on most dyed gems. The cleaning of these gems should be done very carefully as well as dyes can sometimes be removed. It's important to understand that the dyes are not permanent.
One of the examples of dyeing is its application to low quality rubies and sapphires (particularly cabochons and Indian star rubies and beads) by using colored oil to hide cracks and improve color.
 
IMPREGNATION AND STABILIZATION: 
Impregnation is the infusion of wax or paraffin into a porous material. Stabilization is the introduction of a bonding agent, usually plastic, into a porous material. For example, impregnation and stabilization are common for turquoise. Highly porous turquoise which may have nice color, but is extremely fragile and very difficult to polish, can be greatly enhanced by resin impregnation. Stabilization results in enhanced hardness, density and color, and reduces the level of porosity.
This treatment is also used for gems such as jade, opal and ammolite.
 
BLEACHING: 
Bleaching treatment is stable and permanent. It removes color rather than adding it. It is also a color enhancement treatment. The treatment commonly used for the following gems, such as pearls, ivories, B-jade and corals. In many cases, to make material whiter, a mild hydrogen peroxide formula is used to even the color. Sometimes bleaching may be applied before dyeing, so that dyes may be applied more uniformly. 
 
PAINTING OR SURFACE COATING: 
Coated gems are those that have been treated with surface enhancements such as inking, painting, foiling, or sputtering of a film to enhance color, improve appearance or add phenomena.
Painting and coating is an age old method of enhancing a gemstone. Coating often used on the gems with low hardness and porous gems to keep the surface from accumulating skin oils and dirt
“Mystic” quartz, for example has a thin layer of titanium applied to the pavilion which causes interference effects and results in a display of rainbow colors.  Coating is occasionally used on diamonds to improve the apparent color of an off-colored stone.
 
WAXING : 
Waxing is a process of coating a surface of a gem. It is coated with colorless wax (or oil). It's done to improve the durability and in some cases appearance. This treatment is used with stones with a vulnerable, porous surface, or those with microscopic surface imperfections whose polish luster can be boosted with it.
It protects from absorbing skin oils and other environmental contaminants.
Though waxing is not permanent it is fairly simple to wax the gem again.
Gemstones that are often waxed are: Jadeite, turquoise, lapis lazuli and rhodochrosite.

FILLING : 
Filling is used on gems with surface fractures or cavities. Materials with same refractive index use as filler it may be resin, glass or any other material.
Close examination under magnification may allow to spot differences in surface luster, or viewing spectral effect in fractures with dark field illumination allows      identification of the filling.

FRACTURE FILLING OF DIAMONDS: 
In diamonds surface reaching fractures could be filled with lead glass.
Lead glass has the refractive index close to that of diamond so that the fracture becomes less visible and clarity of diamond is improved. 
Filler can be damaged by heat, ultrasonic cleaning, and by re-tipping. The filling does not repair the inclusion; it just makes it less visible. 
The advantages are that it improves the appearance and feel of a gemstone. A disadvantage is that this is not a permanent change and over time the color of the filling may change, showing discolored areas on a gemstone.
Commonly filled gemstones: sapphires and diamonds.

LASER DRILLING OF DIAMONDS:
During the growth of diamond it often has dark inclusions present, usually consisting of graphite/sulfide and/or other iron-containing minerals. Diamonds with visible dark inclusions are less attractive than those with light or transparent inclusions. There are two known methods for reaching a dark inclusion which is completely sealed inside the diamond:
1) Traditional laser drilling and 
2) Internal laser drilling (KM Treatment)
 
1) TRADITIONAL  LASER DRILLING : This process is as follow:
A high-power laser beam (1064nm solid state) focused on a dark inclusion in diamond. 
The laser beam hits the inclusion and bounces back creating a tiny channel, or ‘drilled hole’, from the dark inclusion to the surface; 
Than the diamond positioned in a vessel  for pressure boiling in acid              
The deep boiling in acid or bleach removes the dark matter and cause the inclusion to be less visible.
The drilled holes themselves appear as fine, straight tunnels from the surface of the diamond to an inclusion. 
 
2) INTERNAL LASER DRILLING (KM TREATMENT): 
"KM laser drilling", or "KiduachMeyuhad" - special drilling in Hebrew, as it was invented in Israel. This treatment has few different options:
It may take advantage of existing fractures to reach the inclusions that do not reach the surface, meaning the drilling process is done completely within the feather fairly invisible even under a jeweler's loupe.
It creates its “own fractures” by shooting not one but series of laser beams focused on the dark inclusion. This creates “fan like” appearance and masquerades the created channels as a fracture.
The next stage is the same as in “traditional” laser drill.
The KM or ILD treatment is much more difficult to detect, since it imitates the nature or hides the channels within existing fractures.

HPHT  (HIGH PRESSURE HIGH TEMPERATURE) :
High Pressure High Temperature treatment (HPHT) is relatively new color changing process. A diamond is exposed to extreme pressure and heat, similar to a diamond’s natural environment. This process is used to turn brownish diamonds into colorless diamonds, or creating fancy colors that are rare in natural untreated diamonds. HPHT treatment is a permanent treatment.  
The final result of this treatment greatly depends on the initial properties and the type of the treated diamond. Nowadays, starting with a brown, grey or light yellow diamond, one can achieve a whole range of colors like intense yellow, to greenish yellow to pink and blue and colorless. 
While the industry organizations and government agencies worldwide require full disclosure of all treatments, it's also strongly suggested to ask for an opinion of qualified independent party, such as Gemological Science International (GSI).

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