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.
[Illustration: 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.
[Illustration: {zodiac symbols}]
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.