Man-Made Gem Materials

The first man-made gem materials dates back a few thousand years; early Romans made glass beads and gems. Since natural materials are also in short supply and often hard to mine, man will look for alternatives. Glass gem substitutes are still with us. Glass can be made in any color and it can take on some interesting effects. But glass lacks durability, it breaks easily and is easily scratched. Also a low refractive index means little brilliance. Foil backings and coatings on glass stones increase their brilliance; these are quite easy to spot.

Somewhere a few hundred years ago, someone solved the durability problem of glass gem substitutes; the doublet was born! The most common doublet has a glass bottom and a thin slice of garnet for the top. These two pieces are bonded together, of course this was with glue in the old days. Garnet doublets are truly amazing. The stone has the luster and hardness of a garnet on the top and it takes on the color of the glass on the bottom. Doublets are common in Victorian and older jewelry. With magnification doublets are easy to identify. There is a definite luster difference where the glass end and the garnet begins. Usually just a little more than the table is garnet. If the stone is unmounted, you can turn it table down and observe a red ring which delineates the garnet portion on the top. Of course you do not see this if the glass portion is red.

A doublet is an assembled stone, it is composed of various parts and assembled together. Triplets were the next logical step in creating gem substitutes. Triplets consist of a crown and pavilion section and have some coloring substance bonding the top and bottom together. Opal triplets are quite common today.

In the late l800’s synthetic corundum (rubies and sapphires) was developed. The chemical formula of corundum is simple: aluminum oxide. It is rumored these stones were reconstituted from naturally mined stones, but these are easily made from the chemical components. This art was refined in Switzerland and synthetic corundum is still used in watch movements. If you are looking at old jewelry, keep in mind synthetics have been available for over l00 years!

A synthetic gem is defined as one that has the chemical, physical and optical properties of the corresponding natural gem material. Many synthetic gem materials have been developed during the twentieth century: spinel, emeralds, alexandrite, chrysoberyl, opal, turquoise, lapis lazuli and quartz (especially amethyst). Some of these are expensive to produce and difficult to distinguish from their natural counterpart. Synthetic spinel is very cheap and used as “birthstones”; fortunately it can be easily identified by a gemologist. More sophisticated methods of making synthetics developed which makes identifying some rather difficult. Expensive synthetics are term “luxury synthetics”. Advertising on these luxury synthetic stones today may call them “created”, “cultured” or “laboratory grown”. Synthetic rubies, sapphires, and emeralds are now mass produced; some are quite challenging to tell apart from their natural counterpart. The inclusions in the stone and fluorescence provides clues to the origin of gemstones; it takes knowledge and experience to tell the difference.

So how are you going to know if you are buying a mined gemstone or a laboratory grown one? It may take you a few years to become expert yourself, so you need to be buying stones from a qualified, experienced, and honest seller. Again it is important to have the seller write down exactly what it is you are buying. If you are on the streets of Bogota, Rio de Janiero or Cairo and you are offered something fabulous for five dollars, know deep in your heart this is not a something for nothing world.

Diamond substitutes have been around about as long as the lust for diamonds has been in human blood. Glass, either coated or by itself is probably the oldest diamond substitute. Colorless natural zircons were used in place of diamonds, but these lack durability. Many other man-made materials have been developed in the quest to sell a cheap “diamond imitation”: synthetic spinel, synthetic garnet materials, YAG and GGG, strontium titanate, synthetic rutile and a few more. None of these withstood close scrutiny by a knowledgeable person as being truly diamond appearing. Then cubic zirconia was developed. It really looks diamond-like and fooled few “experts” for a while. Today there are diamond testing machines that actually test the conductivity of the material being tested. If it is a diamond the machine’s needle points to diamond; if it is something else the needle indicates that.

Close scrutiny is required to see the difference between cubic zirconia and a diamond. A cubic zirconia has a much higher specific gravity than a diamond; if it is loose, it can be weighed and will weigh about 70% more that a diamond would if it had the same diameter. If a diamond is a round brilliant and well cut, it can be placed down on print and the print will not be visible through the diamond; with a cubic zirconia the print will be visible through the stone. This test does not work on fancy cuts.

The surface of the girdle is another indication of whether a stone is a diamond or not; most diamonds have a characteristically rough girdle; this has not been successfully imitated by other stones. But this will not be an indication on a stone with a faceted or polished girdle. Cubic zirconia does not have the hardness of a diamond and could be scratched with a hardness point of “9”; destructive tests are discouraged in the gem business. Naturally occurring flaws in a diamond also indicate it is a natural stone.

Synthetic diamonds were developed in the first half of the twentieth century. Today there is capability of producing synthetic gem quality diamonds. But man made stones are not things that romance is made from: there is no passion in a test tube. Where is the thrill of discovery in man made gems? Gems found in Mother Nature have been formed in the heat of passion of volcanoes and the Earth’s other dynamic flow and liquids. Romance! That’s what a natural stone offers.

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Copyright © Sondra Francis, G.G. 1999
About the Author
Sondra Francis has scoured every major colored gemstone market in the world since 1978. She was a charter member of the American Gemstone Association and served as a board member. She was a founding member of the International Colored Gemstone Association. A true gem lover, Sondra has marketed her treasures on the wholesale and retail markets.
Acknowledgments: A special thanks to Pam Dulgar, Alex Edwards, Cheryl Kremkow, Kate Kirby, Helen Mitchell, Carol Morgan Page, David Pond, Elaine Proffitt, and Ray Zajicek for their help.
Photographs: Bart Curren and ICA Gembureau; Alex Edwards, Pearl Sales Institute; David Dikinis