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Which is the best to buy: natural, enhanced, imitation, artificial
or synthetic gems? The answer depends on how you plan to use it.
Natural gemstones have not had anything done to them that changes
their color, stability or durability. They may only be polished or
cut to show off their beauty. Natural stones often have
imperfections in them, and can be quite expensive.
Many gemstones are enhanced, which may improve or change the color,
provide stability or increase durability. Stability means that the
stone won't change color under normal conditions. Durable stones
won't scratch or break when worn. The four main methods of
enhancement are heat treatment, irradiation, chemical treatment and
assembly. While some enhancements are done with an intent to
deceive, many gemstones would not be usable in jewelry if they
weren't treated in some way.
The results of heat treatment and irradiation often mimic what
Mother Nature would have achieved had the stones been left in the
ground a few more centuries. Chemical enhancements are generally
used to change the surface characteristics of gemstones and assembly
is often used to protect fragile stones.
Heat treatment is commonly used to improve color. Color changes
resulting from heating are permanent in most gemstones. Amethyst,
ruby, sapphire, topaz, tourmaline and zircon all are routinely
heat-treated. Most aquamarine now sold has been heated to change it
from its natural green to the blue that is currently popular.
Irradiation is also used to change or deepen gemstone colors. Clear
topaz is irradiated to produce blue topaz, and colorless tourmaline
may be changed to any one of several colors. Some diamonds are
irradiated to improve their color. Irradiation is not always
permanent; some irradiated stones revert to their natural colors
when exposed to extreme heat or light.
Heat treatment and irradiation are generally undetectable.
Chemical treatment of gemstones includes bleaching, dyeing and
staining. It also includes the uses of oils, waxes, resins or
plastics to stabilize or change the appearance of a gemstone.
Chemical treatments are often called impregnation, because the
chemicals usually penetrate the surface of the stone. Porous stones,
like turquoise, are frequently sealed with wax or resin to keep the
color from fading. Oils, waxes and plastics are used on many stones
to hide small scratches and surface flaws. Coral, ivory and pearls
may be bleached. Nearly all gemstones can be dyed or stained. Some
chemical treatments are 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
the stone--synthetics are usually flawless, while natural stones
contain imperfections. Alexandrite, amethyst, coral, diamonds,
emeralds, jade, lapis lazuli and opals are a few of the synthetic
gemstones available. Reconstituted gems fit into a separate
category. Although they do contain genuine material, experts regard
them as imitation. Reconstituting, or reconstructing, means that
small fragments of gem material have been combined to form a large
piece. Amber and turquoise are two common examples.
Reconstituted amber, typically called ambroid or pressed amber, is
made from scraps and shavings generated by amber carvers. The tiny
pieces are collected and heated, then pressed into large blocks.
Manufacturers of ambroid can easily insert insects to make it look
even more like natural amber.
Reconstituted turquoise is made from inferior grades of turquoise
that have been powdered. The powder is mixed with an adhesive and
dye mixture to form a solid mass, which is then cut into shapes.
Although there is a special pleasure in working with natural
gemstones, they aren't always the best choice. Purchase your gems
from a reputable dealer, then select what will best fit your needs.
****Sandra I. Smith, Writer ****
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