SYNTHETIC STONES
For over 200 years mineralogists have been devising techniques for producing synthetic minerals in the laboratory, and attempts have been made, sometimes with considerable success, to apply these techniques to the production of synthetic gemstones. To qualify as a synthetic gemstone the man-made product must be identical chemically and structurally with its natural counterpart. Sapphire, ruby, spinel, emerald, and rutile in gem quality have been brought to commercial production.
Two of the basic techniques used in producing synthetic gems are the flame-fusion and the hydrothermal processes.
The Verneuil furnace, for making synthetic gem rough. A mixture of hydrogen (H) and oxygen (O) burns almost explosively, heating the fusion chamber (F) to high temperatures. For example, powdered aluminum oxide and coloring agents are sifted down from hopper (A) to the fusion chamber and form a cylindrical boule (B) on an adjustable stand (C).
In the flame-fusion process—invented in 1904 by the French chemist Verneuil—powdered aluminum oxide, containing coloring agents, is sieved down through the flame of a vertical blowtorch furnace. As it passes through the flame, the powder melts and accumulates as drops on an adjustable stand just below the flame, where it forms a single crystal boule of the synthetic rough. In a few hours a boule of several hundred carats can be formed. When such furnaces are operated in banks of several hundred units, the commercial production of corundum alone becomes possible at the rate of many tons a year. Through the years, of course, refinements have been made on Verneuil’s original furnace.
In the hydrothermal process, which differs greatly from Verneuil’s flame-fusion process, crystals are grown from solutions of the raw materials that have been subjected to varying conditions of very high pressure and temperature. Some of the quartz used for electronics purposes also is manufactured in this way.
Since chemical composition and crystal structure are the basic characteristics by which a gemstone is identified, and these characteristics are identical in both the manufactured stone and its natural counterpart, the synthetic gemstones offer a very serious challenge to those concerned with gem identification.
5
GEM LORE
All sorts of magic and symbolic properties have been ascribed to gemstones through the ages; for example, the cat’s-eye has been prescribed as a cure for paleness, citrine has been worn as a protection from danger, and the opal cherished as the symbol of hope. The result has been the creation of an intricate, chaotic, and contradictory but interesting mass of gem lore.
Among the treasures in the Smithsonian’s Museum of Natural History is a very old silver breastplate that once was in an ancient synagogue and supposedly was modeled after the one worn by Aaron, the first high priest of the Hebrews. In this plate are mounted twelve stones representing the Twelve Tribes of Israel. Among Christians, the Twelve Apostles also were represented symbolically by precious stones.
THE TWELVE TRIBES Levi, Garnet Zebulon, Diamond Gad, Amethyst Benjamin, Jasper Simeon, Chrysolite Issachar, Sapphire Naphtali, Agate Joseph, Onyx Reuben, Sard Judah, Emerald Dan, Topaz Asher, Beryl
THE TWELVE APOSTLES Peter, Jasper Andrew, Sapphire James, Chalcedony John, Emerald Philip, Sardonyx Bartholomew, Sard Matthew, Chrysolite Thomas, Beryl James the Less, Topaz Jude, Chrysoprase Simon, Hyacinth Judas, Amethyst
The number “12” seems to follow a chain of gemstone superstitions. Gemstones were considered to have mystical relationship not only with the Twelve Tribes and the Twelve Apostles but also with the Twelve Angels, the Twelve Ranks of the Devil, and the Twelve Parts of the human body.
Some stones were even endowed with astrological significance and were believed to be in sympathy with the twelve zodiacal signs. On the basis of an elaborate system of prognostications, an astrologer was considered able to foretell future events by proper observance of changes in hue and brilliance of the symbolic stones.
Aries the Ram, Bloodstone Taurus the Bull, Sapphire Gemini the Twins, Agate Cancer the Crab, Emerald Leo the Lion, Onyx Virgo the Virgin, Carnelian Libra the Scales, Chrysolite Scorpio the Scorpion, Aquamarine Sagittarius the Archer, Topaz Capricornus the Goat, Ruby Aquarius the Water Bearer, Garnet Pisces the Fishes, Amethyst
Perhaps in our own space-oriented times the ancient superstitions sympathetically relating certain gemstones with the planets will be revived. In the distant past, moonstone, topaz, and other white stones were believed to be in sympathy with the Moon, diamond and ruby with the Sun, jasper and emerald with Mars, amethyst, topaz, and emerald with Venus, carnelian, topaz, and amethyst with Jupiter, turquoise and sapphire with Saturn, and rock crystal, agate, and emerald with Mercury. Since Uranus, Neptune, and Pluto were unknown to the ancients, these planets have not been represented by gemstones.
Of special interest to the American public are birthstones. Many birthstone lists have been proposed, and in order to use this idea to popularize gemstones the American jewelry industry has agreed upon an official list. This list has served to bring about some uniformity in the selection of birthstones for the twelve months.
January, Garnet February, Amethyst March, Aquamarine or Bloodstone April, Diamond May, Emerald June, Moonstone or Pearl July, Ruby August, Peridot or Sardonyx September, Sapphire October, Opal or Tourmaline November, Topaz or Citrine December, Turquoise or Lapis lazuli
All these associations and strange beliefs have served to create in the general public a mental image of gemstones that gives to them an increased exoticism and mysterious appeal far exceeding their monetary value.
6
PRINCIPAL GEM SPECIES
An excursion into the literature of gems would reveal that there is much to be discovered about them other than the cold facts of gemology, techniques of gem cutting, and tales of gem lore. When all the information about an individual species is assembled, it provides a sketch of a fascinating gemstone personality. Whole books have been written about diamond—books filled with essays on its mining history, natural occurrences, scientific significance, and best known cut stones.
In the following sections of this book, some of the facts about several of the better known gem species have been gathered. The treatment is not meant to be complete, but enough information is given so that the Museum visitor may better understand and remember what he has seen.
For each species described there are color illustrations of certain gemstones displayed in the collection. Several photographic and artistic techniques have been used to emphasize the various aspects of the beauty of these stones, many of which are the largest and finest of their kinds known; however, not all of the finest gems are pictured here.
At the end of this descriptive section is a list of the significant faceted gemstones in the collection. Obviously, this list will change, because new gemstones constantly are being acquired.