Treatments and Enhancements in Gemstones
Heating is the most common treatment available. It can cause the colour 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 colour 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 colour of the sapphire could be dramatically changed.
Oiling of emerald is universal, but not EVERY emerald is oiled, (fine untouched specimens will command high prices). The colourless oil seeps into the fissures on the surface of the emeralds. When the fractures contain the oil they are less eye visible. To complete this process oil is pressurized into the fissures of the polished stone. This is something that must be accepted; it's the way it is! The only way you will find an emerald that isn't oiled is if there are no fractures at the surface of the emerald, so no oil can get inside the stone. If colour is equal, obviously you will pay more for an emerald if it has no fissures that reach the surface; they simply will have fewer inclusions. If an emerald that originally had fissures that reached the surface, is put into an ultrasonic or is steamed clean, then the oil may be leached out and fractures. This will make the surfacing inclusions appear whiter and more obvious. In this case, the stone can be re-oiled.
Recently, I have read articles that other colored stones such as rubies, alexandrite, other varieties of chrysoberyl, and demantoid garnets have been treated with oils and resins to make surfacing inclusions less visible. Occasionally colored oils are used on emeralds and rubies. The idea is to add colour while concealing fractures. You want to avoid buying these because you can't judge the true colour or know how bad the fractures are. This is done to deceive the buyer. Fortunately this is not common and it is unlikely you will encounter this if you buy from a reputable source. Synthetic resins can be used to fill in fractures in emeralds and other stones with fractures that reach the surface of the gem. Hardeners are often applied to make the process more permanent. The use of these resins, with hardeners (Like Opticon) are NOT acceptable treatments.
Japanese cultured pearls, which are grown in an Akoya oyster grow into a limited selection of colours with various overtones of colours. If they are dark gray, bluish, violet, nearly black, or intense bronze, assume they are dyed. To meet current demand for pearls with rose overtones, some cultured pearls have been given a pink tint; this can be detected by looking for concentrations of dye around drill holes or around blemishes. On the other hand, South Sea cultured pearls which are generally larger than the Japanese cultured pearls, may grow into a variety of exotic colours naturally because they are grown in a different variety of oyster.
Tahitian black pearls are a good example of naturally colored black pearls. Cultured pearls with a natural exotic colour will command a much higher price than a dyed one. Dyeing of chalcedony and of pearls is prevalent, permanent, and acceptable. These colours do not occur in nature; no deception is involved. Coral beads may also be dyed. The suspect coral that has a very intense colour, coupled with an inexpensive selling price.
Impregnation and stabilization
Impregnation and stabilization are common for turquoise. 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. Of the two processes, stabilization is the most permanent. Impregnated pieces must be kept away from heat or the wax could melt & leak... not a pretty sight !!. Some gems are waxed on the surface to enhance lustre but this is not very usual. The upside for stabilized turquoise is that it will not absorb oils and discolour as untreated turquoise may.
Opal can be stabilized with plastic to hide crazing, but this is not common at all and would only be done to deceive the buyer.
Bleaching is a process for organic gem materials such as ivory, coral, and for pearls and cultured pearls. It lightens the colour and is permanent and undetectable. No price difference exists as a result.
Irradiation means pounding material with subatomic particles or radiation. Sometimes irradiation is followed by heating to produce a better or new colour for the gem This second step is also known as a “combination treatment. . Blue topaz is the most common example. Although blue topaz occurs in nature, it is quite rare and pale in colour. Off colored diamonds can be irradiated and heated and turned into intense greens, yellows, blues, browns & pinks. These stones are fairly common. Cultured pearls can be irradiated to produce gray or blue colours; but dyeing in these colours is more common. Varieties of quartz, Corundum, beryl and spodumene are irradiated and subsequently annealed with heat to produce dramatic and desirable colours.
Diffusion was originally used on sapphires. Chemicals, like beryllium, were infused at high temperatures, and actually penetrated the gems. Early diffusion only produced colour 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 colour, change colour, or create asterism (stars).
Filling is used on gems with surface fractures or cavities. Glass, plastic or other materials are used to fill these holes. This treatment is done to rubies, sapphires and Diamonds. With close examination with magnification you may be able to spot differences in surface lustre, or see a spectral effect in fractures when viewed with dark-field illumination. Filler can be damaged by heat, ultrasonic cleaning, and by re-tipping The AIGS, The Asian Institute of Gemmological Sciences, has done extensive research on filled rubies.
Lasering is sometimes used on diamonds. The process drills very tiny holes into a diamond to provide access to an inclusion which detracts from the beauty of the stone. The inclusion can then be, vaporized or bleached to make it less obvious if it is not burned out by the lasering. Under magnification laser holes are visible when viewed at the correct angle. A lasered diamond would be classified in the slightly imperfect or imperfect category regardless of the improvement in apparent clarity and should be priced accordingly. Diamonds are the only gemstones to be treated in this fashion, in part because only they can withstand the heat of a laser.
High Pressure, High Temperature (HPHT) Treatment
Heating a diamond to high temperatures under high confining pressures to remove, or change its colour.
Heating diamonds at high pressures and high temperatures can remove or lessen their brownish coloration so the gem becomes colourless.
Gems that are Not Enhanced
There are some gemstones that are not known to be enhanced. These include: Garnets,(with the exception of demantoid), Peridot, Iolite, Spinel, varieties of Chrysoberyl, Tourmaline (with the exception of the Paraiba variety), Malachite, Hematite, and Feldspar with the probable exception of varieties of andesine and 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.All our gemstones are thoroughly and carefully checked for the above treatments by our team of certified gemmologists before adding it to our stock, to give our customers the most Genuine, Authentic and Effective Jyotish standard gemstones.
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