- Infilling Diamonds
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.
Oiling of emerald is universal, but not every emerald is oiled. When the rough emerald is mined it is thrown into a barrel of oil; when it is cut, oil is used as a lubricant on the cutter’s lap. The colorless 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. 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 color 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.
Irradiation means pounding material with subatomic particles or radiation. Sometimes irradiation is followed by heating to produce a better or new color for the gem. Blue topaz is the most common example. Although blue topaz occurs in nature, it is quite rare and pale in color. In the United States irradiated gems are regulated by the Nuclear Regulatory Agency to in an attempt to insure there is no harmful residual radiation.
Filling is used on gems with surface fractures or cavities. Glass, plastic or other materials are used to fill these holes. This is sometimes done to rubies. With close examination with magnification you may be able to spot differences in surface luster, or see a spectral effect in fractures when viewed with dark-field illumination. The AIGS, The Asian Institute of Gemological 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.
Bleaching is a process for organic gem materials such as ivory, coral, and for pearls and cultured pearls. It lightens the color and is permanent and undetectable. No price difference exists as a result.
Coating is a method of enhancement that can vary widely 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.Coatings allow for a wide range of colors and effects to be applied to natural stone materials. Colorless topaz can be coated blue to resemble blue topaz that is typically irradiated, and colorless quartz can be coated purple to resemble amethyst, but most often coatings create new colors and effects that cannot be found in nature.
Diamonds with inclusions are sometimes filled with glass to make them appear clearer. Oved and Yehuda Diamonds have undergone this treatment. 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. If you look at a filled diamond closely, rotate it under light, you should be able to notice a bluish flash. Both Yehuda and Oved will usually refill your diamond for free if it is ever damaged. Check for guarantees before buying such a diamond.