DOES IT MATTER IF IT'S NOT NATURAL?

permanent. Others will dissolve in solvents like acetone or in ultrasound cleaners. Waxes melt when exposed to heat or strong light. Bleaching can be impossible to detect. Dyeing can usually be detected with a microscope.

Assembled stones may be composites like doublets and triplets, or they may be foilbacks. A composite stone is two or three pieces of material fused or joined by colorless cement. Although any stone may be made into a composite, opals are the best-known. An opal triplet consists of a piece of good opal sandwiched between a top layer of clear quartz and a bottom layer of low-quality opal. A doublet is usually good opal underneath a quartz layer. The quartz helps protect the delicate opal. Composites also allow the use of gemstones too small to be used otherwise.

False composites contain no gemstone material. False opal doublets are made from crystal cemented over abalone shell.

Foilbacks have been made for nearly 4,000 years, using a variety of techniques. One kind of foilback involves placing a backing of foil or a metallic coating on a stone to give it a more brilliant color. Cat's-eyes and star effects are created with etched backings. Rhinestones are one example of a popular foilback.

Imitation, or simulated, gemstones may be natural (substitutes) or manmade (artificial). Substitutes are cheaper look-alike stones. Red spinel or garnets may be substituted for ruby, and green tourmaline is used to replace emerald. Cubic zirconia, a manmade stone from a natural substance, is a well-known substitute for diamond.

Glass is a time-honored way of making gems. Glass imitations have been found in Egyptian tombs that are at least 5,000 years old. Non-transparent glass was first used to make artificial turquoise, lapis lazuli and onyx. Artificial gemstones of all varieties were later made from paste, which is a very hard kind of transparent glass. Glass is often used now to make artificial jade and opal. Plastic is also frequently used for artifical gems, particularly the organic ones like amber, ivory and coral.

A synthetic gemstone is laboratory-grown, or manufactured. All the chemical, physical and optical characteristics of synthetic gemstones are identical to their natural counterparts. Good synthetics have been made since the early 1900's. Because they mimic natural stones so well, most synthetics are difficult to detect, even by experts. Often, the only clue is the physical perfection of

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