Most gemstones are natural, mined from the earth. Some gems are synthetic and are made in a laboratory. But these days many gems are natural material which is enhanced by a variety of ingenious methods.

The most common technique for enhancing the color and clarity of gems is heat treatment. Heat treatment is an ancient art that has become well accepted in the trade. Indeed, the vast majority of sapphires and rubies in the market have been heat treated. A number of other gems, including tanzanite and blue zircon are also routinely heat treated.

Other methods of gemstone enhancement are of more recent vintage and involve application of quite sophisticated technology. The most dramatic of these new methods uses a high tech coating technology to turn colorless topaz and quartz into brilliant designer gems.

The technology of thin-film deposition is widely used in the optics industry for reflective and non-reflective coatings, and in the electronics industry for building up the layers of integrated circuits in semiconductors. The technology involves depositing an extremely thin layer of film on a substrate material, where the film layer may be only a few microns thick.

In the gemstone industry, the thin metallic film is applied to the pavilion of the gemstone, so that the interesting color effects are reflected from the crown. The film is molecularly bonded to the substrate, effectively becoming part of the topaz or quartz material. The film is hard and durable, and since it is applied only to the pavilion of the stone, it cannot be affected by scratches on the crown.

The most well known gems produced by this method are usually sold under the names Mystic Topaz and Mystic Quartz. They display a prismatic rainbow effect. Some brilliant blue and pink topaz is also produced in this way. These inexpensive gems have no pretensions and are typically used to make fun and colorful jewelry. But these gems are natural topaz or quartz, with all the virtues of those gem materials. In the future we may see more valuable gemstones optically modified using thin film deposition techniques.

The coated gems are very durable and do not require any special care. They should not be exposed to abrasives, acids or harsh chemicals. They are best cleaned with just mild soap, water and a soft brush. However, coated gems cannot be recut or repolished, since the coating would be affected.