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Decorative
Stones
Spinels tend to have fewer flaws than corundum gems
of comparable color, size, and quality. However, large
rough spinels are quite rare and might be fit for museum
display. The Diamond Treasury in Moscow contains a huge
deep-red spinel, clear, transparent, and irregular shape.
It is set at the top of a crown made for the Princess
Catherine II 1762. The stone weighs an estimated 400
carats. A gem of 105 carats in the collection of the
Louvre in Paris, and the British Museum of Natural History,
London, displays a polished mass from Burma ill, weighs
520 carats.
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Cut
spinels weighing more than ten carats can I can be considered
rare gems. Although they are available, few cut spinels
a sold because of the almost complete unfamiliarity
with spinel on t1 part of the general public. |
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The
world's most notable localities for gem spinel are the gem
gravels of Sri Lanka and Burma. The gem rough may occur as
perfect crystals, waterworn pebbles, or large irregular lumps.
Other localities include Afghanistan, Thailand, Australia,
Brazil, and the United State ¬Many historically important
stones came from the ruby mines of Badakshan, Afghanistan.
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DIAMONDS,
GEMSTONES & CRYSTALS
FACTS & FIGURES |
| Synthetic
spinels have been manufactured since about 1915.
The colors produced are generally designed to
mimic the appearance of other gemstones, such
as aquamarine and tourmaline, rather than the
natural colors of spinel or corundum! Synthetic
spinels are common, seen in class rings and inexpensive
birthstone jewelry, usually labelled (erroneously)
in quotes, such as "tourmaline" or "topaz."
Consumer
Tips-A buyer's suspicions must surely be aroused
when "topaz" in a 14K gold ring is priced
at $40 or less, since a precious topaz of the
same size and color might easily sell for ten
times that amount Spinels occur in such a wide
variety of natural colors that they could easily
be mistaken for other gems. Since they are very
hard, lovely, an, durable, spinels should be more
popular than they are, their current neglect is
due to a lack of exposure to the public by the
jewelry trade.
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Zircon
Records of the first uses of zircon as a gemstone
are hidden in the dark shrouds of a forgotten
past. Carved zircons have been recovered from
w of the most ancient of dated archaeological
sites, and zircon may been the earliest used of
all gems. It appears in the Bible and it recurs
through world literature under a variety of names,
including with, hyacinth, and jargoon. Zircon
was respected in the Middle Ages '' supposed curative
powers. |
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There
are three distinct types of zircon, generally known as high,
medium, and low. The chemical composition is basically zirconium
silicate, but the presence of radioactive elements in the
structure and its complex mode of formation makes zircon one
of the more interesting minerals. In addition, zirconium metal
is extensively used in space age alloys with sophisticated
applications. Non-gem zircon is before mined in large quantities
for its zirconium content.
For
gem purposes high-type zircon is the most important. The primary
sources are Cambodia and Thailand, where it is found as waterworn
, pebbles colored reddish-brown to yellowish-brown. The pebbles
are heated in primitive coal-burning ovens, sometimes several
times. The treatment causes a color change, producing blue,
golden-yellow, and Colorless material. Bangkok is a cutting
and heating center for zircon. Occasionally red or orange
stones appear on the market, but these colors are natural
in origin and not produced by heating. |
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