|
|
|
|
Garnet
Uvarovite is deep green in color. Transparent material
suitable for mg, however, is extremely rare, and only
tiny cut gems exist. Crys¬tal occur in various parts
of the world, but large crystals with gem potential
occur only in Finland and the U.S.S.R.All of the garnets
that occur in nature can be classified as one of six
major garnet species. Many color varieties, however
,have been given special names that are widely used.
Essonite, or hessonite, isOrangy-brown or brownish-orange
grossular.
|
|
Large
gems have been cut from crystals found at the Jeffrey
Asbestos Mine at Asbestos, Quebec. Rhodolite is a garnet
with a chemical composition between pyrope and -~dine.
Its color is violet-red or purple, the hue sometimes
resem¬'hat of amethyst. Good rhodolite is scarce
and expensive comto most other garnets. |
| |
|
Localities
include Brazil, Ceylon, and with some purple material known
from Cowee Creek, North Carolina. "Transvaalite,"
or "Transvaal jade" is a name given to a massive
form of grossular. This material, green in color. does bear
resemblance to jade, although its value is much inferior.
Localities :e South Africa and Canada. Massive white grossular,
suitable for carving, has been found in Burma, associated
with jadeite.
|
|
 |
 |
|
DIAMONDS,
GEMSTONES & CRYSTALS
FACTS & FIGURES |
| Almandine
containing fibrous inclusions occurs in Idaho.
When cut into Cabochons this material produces
four-rayed and six-rayed stars that make curious
and attractive collector items, as well as beautiful
59 Spessartine from.Modern technology has produced
a host of new and exotic crystal¬line materials
designed chiefly for use in semi-conductor and
laser work. Among these compounds are some materials
that have the same basic atomic structure as the
natural garnets. However, being laboratory products,
they have chemical compositions that do not correspond
to any garnets produced by nature. Some of these
so-called "synthetic garnets" have optical
properties that make them suitable for use as
simulated diamonds. These are discussed on page
146.
Consumer Tips-Garnet is the birthstone for January,
and inexpensive red garnets are plentiful and
readily available. In spite of this, much birthstone
jewelry features synthetic gems, either corundum
or spinel, designed to resemble garnet. Since
these synthetics have very little intrinsic value,
it is worthwhile insisting on natural garnets
if the posses¬sion of a natural gem is at
all important to the buyer.
Grossular
garnets in shades of yellow, orange, and green
are rarely seen in the gem trade. For this reason
untrained sales personnel may regard with suspicion
such gems brought into a jewelry shop for evalua¬tion
or appraisal. The gem's owner should remember
that such a task requires the talents of a trained
gemologist, and not be upset by random opinions
as to the lack of authenticity of a stone. A good
example of this is the case of vanadium grossular,
which could easily be mistaken for emerald. For
someone who is unaware of the color range of natural
garnets, it is hard to imagine that a gem of such
rich and beautiful a green hue could be a garnet.
The same, could be true of yellow, orange, and
colorless stones. |
|
|
 |
Many
reddish garnets are called rhodolite in the gem trade, whereas
they may actually be almandine or pyrope. Since a chemical
analysis may be needed for certain identification, color is
not a suitable criterion to establish a species or variety
name for a given gem. If a high-price premium is attached
to the stone because of its supposed identity, 60 verification
of this identity might be worthwhile before purchase. |
 |
 |
 |
| diamond
1 | 2
| 3 |
|
|
|
