Garnet Informations:
Color: The versatile garnet comes in a virtual rainbow
of colors, including pink, red, purple, orange, yellow, violet, green,
colorless, occasionally black, brown and many shades of red and green.
The most common color of garnets is reddish brown. Bohemian Garnet is
deep red gemstone, Russian Demantoid and African Tsavorite are vibrant
green.
Description: Pyrope: Mg3Al2[SiO4]3. Garnets are a group
of common silicate minerals that have similar crystal structures and
chemical compositions.
It can be translucent to transparent, sometimes opaque with a vitreous
or resinous lustre. The best known type of garnet is red semi-precious
stone pyrope, one of several red gems, which the ancients used to call
Carbuncles.
Garnets are actually one of the largest families of gemstones. Most
natural garnets are mixtures of two or more of the following pure species:
pyrope, almandine, spessartine, uvarovite, grossular, andradite. Garnets
occur in a very wide variety of formations, colors, and clarities.
The name's origin: Garnets were so called by the ancient
Greeks since color reminded them of the pomegranate seed or granatum.
Birthstone: The garnet is considered to be the birthstone
for Capricornus (Goat): Dec. 22 - Jan. 19.
Varieties: There are following major types of garnets:
Almandine, Pyrope (also called Bohemian garnet, or Cape ruby), Spessartine,
Grossular (also called grossularite, or Gooseberry garnet), Andradite,
Rhodolite, Carbuncle, Hessonite (also called essonite, or Cinnamon stone),
Topazolite, Uvarovite and Uralian emerald (or demantoid).
Care and treatment: Clean garnet with a dry soft cloth.
As with all gemstones, care should be taken to protect it from scratches,
sharp blows, harsh chemicals and extreme temperatures.
From the stone history: One of the world's most ancient
gems, garnet has been treasured for thousands of years.
Use of garnets as gems is traced to the Nile Delta in 3100 B.C. Egytian
artisans created beautifull garnet beads, bracelets and other jewelry.
Garnets since ancient times used widely as an abrasive. Garnets are
said to have been used by Asiatic tribes in place of bullets.
During the latter part of the 19th century, garnet bracelets and brooches
were particularly popular. Most familiar during the peak of popularity
were varieties of pyrope.
The hardness of garnets and their sharp fracture make them suitable
as abrasives for wood, leather, glass, metals, and plastics.
Garnet varieties have become known by misleading names, frequently consisting
of a locality with the name of another mineral variety, such as Uralian
emerald or Cape ruby.
Shopping guide: Garnet is a reasonably priced stone.
It is beautiful in rings, pendants, necklaces and bracelets. There are
some beautiful orange garnets. A green tsavorite garnet is a very rare
and high-priced stone.
The dazzling beauty of garnets is responsible for their widespread use
as gemstones.
Healing ability: Garnet is an excellent assistance for
blood deficiency diseases. It stimulates bloodstream and pituitary gland,
relieves rheumatism and arthritis pain.
Garnet combats depression and lethargy. Garnet also stimulates the spleen
properly. Garnet protects against depression and impure thoughts. Cures
fever and promotes good health.
Mystical power: Garnet should be carried close to the
body. Its energy is balancing and peaceful. This stone of passion stimulates
the sexual drive. Garnet gives energy and courage. It is said to encourage
robust good health and sexual desire, enhance the wearer's imagination.
Garnet symbolizes fire, faith, courage, truth, grace, compassion, constancy
and fidelity. It also offers protection to the traveler.
Deposits: Garnets are
found in a wide variety of locations including Kenya, Sri Lanka, Thailand,
Brazil, India, Madagascar, Canada and USA. In USA garnet has been obtained
in Arizona, Colorado, Georgia, Idaho, New Hampshire, New Mexico, North
Carolina, Pennsylvania, Utah, Florida, California and Virginia. The
majority of today's Garnet supplies come from Africa. Notable quantities
of garnets have been also found in Czech Republic and Spain.
The oranges and browns of Spessartite and Hessonite hail from Namibia
and Sri Lanka.
Hardness
Because the chemical composition of garnet varies, the atomic bonds
in some species are stronger than in others. As a result, this mineral
group shows a range of hardness on the Mohs Scale of about 6.5 to 7.5.
The harder species, like almandine, are often used for abrasive purposes.
Garnet group endmember species
[edit] Pyralspite garnets – aluminium in Y site
Almandine: Fe3Al2(SiO4)3
Pyrope: Mg3Al2(SiO4)3
Spessartine: Mn3Al2(SiO4)3
Almandine
Almandine in metamorphic rock
Almandine, sometimes incorrectly called almandite, is the modern gem
known as carbuncle (though originally almost any red gemstone was known
by this name). The term "carbuncle" is derived from the Latin
meaning "live coal" or burning charcoal. The name Almandine
is a corruption of Alabanda, a region in Asia Minor where these stones
were cut in ancient times. Chemically, almandine is an iron-aluminium
garnet with the formula Fe3Al2(SiO4)3; the deep red transparent stones
are often called precious garnet and are used as gemstones (being the
most common of the gem garnets). Almandine occurs in metamorphic rocks
like mica schists, associated with minerals such as staurolite, kyanite,
andalusite, and others. Almandine has nicknames of Oriental garnet,
almandine ruby, and carbuncle.
Pyrope
Pyrope (from the Greek pyropós meaning "fire-eyed")
is red in color and chemically a magnesium aluminium silicate with the
formula Mg3Al2(SiO4)3, though the magnesium can be replaced in part
by calcium and ferrous iron. The color of pyrope varies from deep red
to almost black. Transparent pyropes are used as gemstones.
A variety of pyrope from Macon County, North Carolina is a violet-red
shade and has been called rhodolite, from the Greek meaning "a
rose." In chemical composition it may be considered as essentially
an isomorphous mixture of pyrope and almandine, in the proportion of
two parts pyrope to one part almandine. Pyrope has tradenames some of
which are misnomers; Cape ruby, Arizona ruby, California ruby, Rocky
Mountain ruby, and Bohemian garnet from the Czech Republic. Another
intriguing find is the blue color-changing garnets from Madagascar,
a pyrope spessartine mix. The color of these blue garnets is not like
sapphire blue in subdued daylight but more reminiscent of the grayish
blues and greenish blues sometimes seen in spinel. However, in white
LED light the color is equal to the best cornflower blue sapphire, or
D block tanzanite; this is due to the blue garnet's ability to absorb
the yellow component of the emitted light.
Pyrope is an indicator mineral for high-pressure rocks. The garnets
from mantle derived rocks, peridotites and eclogites, commonly contain
a pyrope variety.
Spessartine
Spessartine (the reddish mineral)
Spessartine or spessartite is manganese aluminium garnet, Mn3Al2(SiO4)3.
Its name is derived from Spessart in Bavaria. It occurs most often in
granite pegmatite and allied rock types and in certain low grade metamorphic
phyllites. Spessartine of an orange-yellow is found in Madagascar. Violet-red
spessartines are found in rhyolites in Colorado and Maine.
[edit] Ugrandite group – calcium in X site
Andradite: Ca3Fe2(SiO4)3
Grossular: Ca3Al2(SiO4)3
Uvarovite: Ca3Cr2(SiO4)3
Andradite
Andradite is a calcium-iron garnet, Ca3Fe2(SiO4)3, is of variable composition
and may be red, yellow, brown, green or black. The recognized varieties
are topazolite (yellow or green), demantoid (green) and melanite (black).
Andradite is found both in deep-seated igneous rocks like syenite as
well as serpentines, schists, and crystalline limestone. Demantoid has
been called the "emerald of the Urals" from its occurrence
there, and is one of the most prized of garnet varieties. Topazolite
is a golden yellow variety and melanite is a black variety.
Grossular
Grossular on display at the US National Museum of Natural History. The
green gem at right is a type of grossular known as tsavorite.
Grossular is a calcium-aluminium garnet with the formula Ca3Al2(SiO4)3,
though the calcium may in part be replaced by ferrous iron and the aluminium
by ferric iron. The name grossular is derived from the botanical name
for the gooseberry, grossularia, in reference to the green garnet of
this composition that is found in Siberia. Other shades include cinnamon
brown (cinnamon stone variety), red, and yellow. Because of its inferior
hardness to zircon, which the yellow crystals resemble, they have also
been called hessonite from the Greek meaning inferior. Grossular is
found in contact metamorphosed limestones with vesuvianite, diopside,
wollastonite and wernerite.
Grossular garnet from Kenya and Tanzania has been called tsavorite.
Tsavorite was first described in the 1960s in the Tsavo area of Kenya,
from which the gem takes its name.[citation needed]
[edit] Uvarovite
Uvarovite is a calcium chromium garnet with the formula Ca3Cr2(SiO4)3.
This is a rather rare garnet, bright green in color, usually found as
small crystals associated with chromite in peridotite, serpentinite,
and kimberlites. It is found in crystalline marbles and schists in the
Ural mountains of Russia and Outokumpu, Finland.
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