Modified: April 2011
by David Federman, GG
What is the key to making a gem the most beautiful it can be? The ancients thought a blend of art and science was needed to unlock gemstone beauty. Brilliance and fire, they said, lie hidden within gemstones and await the cutter's art to be released. That art consisted of shaping, faceting, and polishing.
But there is more to gemstone beauty than the ability to glitter and glow. Gemstone beauty also consists of fine color and clear complexion. The ancients believed that science could help gems attain the finest color and appearance, and the enhancements that they developed remain essentially the same today--if not in practice, surely in principle.
Put simply, enhancement allows the jewelry industry to use various forces of nature, like heat, to unlock the inherent beauty residing within a gem.
In recent years, ancient gem-improvement technologies like heating have been used to produce gem colors in no other way possible. Most tanzanite, for example, comes from nature a rather drab brown. Once subjected to mild heating, however, these stones turn handsome shades of blue and violet.
What's more, the science of gem beauty has advanced to the point where the jewelry trade can harness other forces of nature, such as irradiation, that the ancients had no way of tapping. In the case of diamond, irradiation produces colors so like those of nature that gemological testing is needed to tell the natural from the enhanced. In the case of topaz, irradiation produces colors far superior to topaz found in nature.
Enhancements have been making gems beautiful for as long as people have been wearing them. So what is an enhancement?
The American Gem Trade Association (AGTA) defines a gemstone enhancement as any process other than shaping, faceting, and polishing "that improves the appearance (i.e., the color, clarity, or phenomena), durability, value, or availability of a gemstone." The process covers a wide range of techniques, from traditional ones like oiling and heating to modern innovations like diffusion and irradiation. Depending on the method used and the gem that receives it, these enhancements can be long lasting and very stable or require special care and handling.
Stable Enhancement Methods
The most stable enhancements permanently transform gems. How? By harnessing forces of nature like heat and irradiation to change a gem's chemistry and physics--usually in a manner that is irreversible under normal wear and tear.
Heating treatments use low-, medium-, and high-temperature heat, usually in a furnace, to alter gemstone color, clarity, and sometimes phenomena. Nearly all of the world's ruby, sapphire, and tanzanite owe their color and clarity to heating. A good many aquamarines are also heated to eliminate traces of green or gray.
Irradiation uses high energy, sometimes followed by heating, to alter gemstone color. Diamonds are frequently enhanced using this method. Some cultured pearls are also irradiated to produce permanent colors that rarely or never occur naturally.
Bleaching uses heat or chemicals to lighten or remove undesired colors in gemstones. Many cultured pearls are bleached to whiten them.
Moderately Stable Enhancement Methods
Some widely used traditional and modern enhancement methods require special care and handling to maintain their beauty.
Oiling infuses colorless oils, resins, or waxes into a gemstone's tiny surface-reaching fissures to hide them and give gems a cleaner complexion. This long-practiced clarity enhancement is used mainly for emerald and jade. The oils used are either natural or have a natural counterpart. If coloring agents are added to the oils, the stones are classified as dyed. Emeralds infused with man-made substances like plastics and polymers that have no natural counterpart are considered impregnated.
Diffusion uses heat and chemicals to produce surface layers of color on a gemstone. The chemicals are ones naturally associated with the gem being enhanced. For example, titanium--nature's coloring agent in sapphire--is added to pale corundum to turn it a beautiful blue. The thickness of the color layer depends on the size of the stone and the amount of processing time. Used exclusively for ruby and sapphire, diffusion produces beautiful color. However, any damage to the stone that might require it to be repolished could reveal the shallowness of its color, so wear with care.
Lattice diffusion uses heat and chemicals to produce deep penetration of color. In this case, the chemicals used are ones associated with other gems. For example, beryllium--found in chrysoberyl but not in corundum--gives lattice-diffused sapphire (corundum) beautiful orange and pink colors. It is an enhancement that should present no problems in normal wear and tear.
Enhancements Requiring Special Care
Space-age technology allows the jewelry industry to offer gems with exotic colors and effects that do not occur in nature. But the spectacular results produced using these high-tech enhancements require special care to maintain them.
Vapor deposition uses a strong electric current to build up and bond special-formula coatings to gemstones, producing unique colors and special effects. This technique is similar to ones that produce lens and eyeglass coatings. Used principally with "mystic" topaz and cubic zirconia, vapor deposition alters the light-absorption properties of these gems to create vibrant colors that are in no other way possible. Although these coatings are very durable, extra care must be taken when wearing and cleaning them.
Jewelry Television® is as committed to education as it is to service and value. The purpose of this article has been to inform gem buyers of both traditional and modern gem enhancements that have either proven their reliability over time or show great promise for the future. Methods about which Jewelry Television® has reservations are not discussed here. For a thorough comprehensive listing and description of present-day enhancements, as well as the gems for which they are used, we invite you to go to JTV.com's Gemstone Enhancement Chart.