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Garnet
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The garnet group is composed of differently colored minerals that have a similar
chemical structure. Different trace elements result in the variation of color
found in this group. This is a very versatile gem group, supplying durable gems
in various colors and at a reasonable price. The most expensive colors are the
green and orange found in the tsavorite, demantoid, and spessartite varieties.
Demantoid garnet is usually found in small sizes; one carat is considered large
for this gem material. It has a high dispersion which means that when cut and
polished, it sparkles like a green diamond. Demantoid garnet was used in
Victorian jewelry and can still be found in some older pieces today. It was
originally mined in Russia, in the Ural Mountains but that source has since
ceased production. New areas being mined in the world do not have the intense
green of the earlier material from Russia. It is characterized by having
"horsetail" inclusions, in this case highly desirable and worth more than
demantoids that do not exhibit this type of inclusion. Demantoid garnet in the
.50ct. to one carat size can cost from $8,400 to $10,500/ct.
Tsavorite garnet is found only in East Africa in a beautiful deep green
color. Very pale material has been found in Pakistan. Anything over five carats
is considered very rare. Commonly one to three carats is normal for this
material. Tsavorite garnet is often used as a substitute for emerald because it
is more durable and has a lovely green color. Prices for four to five carat
sizes vary from $6,600-$8,400/ct. One to three carat sizes go from
$3,000-$6,900/ct.
A new find in Africa of spessartite garnet has produced an orange color
compared to "Fanta orange drink" color. It is a bright color that is quite
striking and beautiful. Prices range from $250-$600/ct.
The other garnet colors are various shades of red with some secondary colors,
usually brown or purple. The prices are moderate, nothing over $300/ct.
Garnet can be synthesized but is not commonly available since it is expensive
to produce. Since the molecular structure is so complex for garnet, it does not
benefit from the usual treatments of heating or irradiation.
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| Sri Lanka, Malagasy Republic, India, Africa,
Russia, U.S. |
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| General composition AlSiO; color varies with added
molecules in structure; cubic crystal system |
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| Transparent to translucent; SR ( although shows
strain or anomalous double refraction in the polariscope) Hardness 7-7
1/2 |
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| Widely available in darker red colors but in
smaller sizes; larger sizes rare in other colors; other colors less
common and moderately available |
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| Red, orange, violet, green, yellow and mixtures of
these colors with brown modifier. |
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| None |
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| Avoid sudden temperature change; fractures fairly
easily |
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| History has confused the red garnet variety with
ruby; colors are similar; birthstone for January |
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| Faceted, often with unusual crown cuts (ex.
checkerboard); cabochon, beads; in large sizes red color becomes overly
dark; smaller sizes predominate |
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Fine quality in red colors; size 3.0-5.0cts=
$300/ct commercial quality $165/ct
tsavorite (green) in sizes 2.0-4.0cts=$3000-6,900/ct commercial quality
$1500/ct
orange-yellow colors in sizes 1.0-3.0cts=$300-600/ct
commercial quality $100/ct |
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