The gemstone Garnet is the official
birthstone for January as adopted by the American National
Association of Jewelers in 1912. Garnet may be given as the
anniversary gemstone for the second and sixth year of marriage.
It is also the stone for the Zodiac sign Aquarius. Garnets range
from a 7.0 to 7.5 on the Mohs scale of hardness and are found in
the U.S. (Arizona), South Africa, Argentina, Australia, Brazil,
Myanmar (Burma), Scotland, Switzerland and Tanzania. Click here
for a picture in natural form.
Click here for a picture in natural form.
Click here for more faceted and natural specimens.
Description:
Garnets as a group are relatively common in highly metamorphosed
rocks and in some igneous formations. They form under the high
temperatures and/or pressures that those types of rocks must
endure. Garnets can be used by geologists as a gauge of how much
temperature and pressure the rock has endured. As a gemstone,
garnets have had a mixed reputation. Garnets do possess high
indices of refraction, are hard enough, have pretty colors, are
wonderfully transparent, lack cleavage and are durable; thus
making good candidates for gemstones. Garnet derived its name
from the Latin word granatus, meaning like a grain and also the
color of the pomegranate seed. Grain refers to the mode of
occurrence wherein crystals resemble grains or seeds embedded in
the matrix. Garnet is a family of minerals having similar
physical and crystalline properties. There are a number of trade
and variety names for garnet, most of these names are for
particular colors of a specie.
Chemistry:
The general formula for most of the garnets is A3B2(SiO4)3.
The A represents divalent metals such as calcium, iron,
magnesium and/or manganese. The B represents trivalent metals
such as aluminum, chromium, iron and/or manganese and in the
rarer garnets; vanadium, titanium, zirconium and/or silicon. The
general formula for a couple of rarer garnets (hibschite and
katoite) is A3B2(SiO4)3-X(OH)4X.
The main differences in physical properties among the members of
the garnet group are slight variations in color, density and
index of refraction. All species of garnet have been used as
gemstones.
- Grossular (also known as grossularite), Ca3Al2(SiO4)3,
Calcium Aluminum Silicate has many color possibilities and
is probably the most colorful of the garnets. It is believed
that these garnets form from the metamorphism of impure
siliceous limestones. Grossular can be colorless, white,
gray, yellow, yellowish green, various shades of green,
brown, pink, reddish, or black. Hessonite is the variety
name for a fine orange, cinnamon brown, or pinkish variety
of grossularite. Tsavorite is the trade name for fine dark
green grossularite.
- Almandine (also known as almandite), Fe3Al2(SiO4)3,
Iron Aluminum Silicate is the most common of the garnets and
is usually the garnet found in garnet schists (a type of
metamorphic rock composed mostly of mica). Pure almandine
and pure pyrope are rare in nature and most specimens are a
percentage of the two. Almandine is deep red, brownish red,
brownish black or violet-red in color.
- Pyrope, Mg3Al2(SiO4)3,
Magnesium Aluminum Silicate is the only garnet that is
always a shade of red. Although less common than most other
garnets, pyrope is a common gemstone. Pyrope is the only
garnet whose most common source is igneous rather than
metamorphic. Most pyrope comes from ultramafic igneous rocks
that contain olivine and/or diamond. Metamorphic pyrope
comes from the metamorphism of the igneous rocks previously
mentioned or from magnesium rich rocks. Almandine and Pyrope
form a series in which iron substitutes for the magnesium in
pyrope. In fact, pure Pyrope is unknown in nature and the
various proportions are referred to as pyrope-almandine
mixes. One mixture of approximately two to one (pyrope to
almandine) is a variety called Rhodolite which has an
attractive red-lavender color and is cut as a gemstone.
Pyrope is commonly purplish red, orangy red, crimson, or
dark red. Pyrope is difficult to distinguish from Almandine
but is usually clear and free from flaws, at least more so
than almandine. Fine-quality Pyrope garnets from
Czechoslovakia are often called Bohemian garnets.
- Spessartite (also known as spessartine), Mn3Al2(SiO4)3,
Manganese Aluminum Silicate like other garnets, forms
rounded crystals with 12 rhombic or 24 trapezoidal faces or
combinations of these and some other forms. This crystal
habit is classic for the garnet minerals. Spessartine is
formed in manganese rich metamorphic enviroments and in some
granitic pegmatites. Spessartine is somewhat rare but
occassionally will accompany other minerals and make a nice
accessory mineral to an outstanding mineral specimen.
Spessartite garnets can be red, reddish orange, orange,
yellow-brown, reddish brown, or blackish brown. Malaya is a
trade name for a pyrope-spessartite that varies in color
from red, through shades of orange and brownish orange to
peach and pink.
- Andradite, Ca3Fe2(SiO4)3,
Calcium iron silicate. Andradite forms in contact or
regional metamorphic enviroments as does grossular, the
calcium aluminum garnet. It is believed that these garnets
form from the metamorphism of impure siliceous limestones.
Andradite garnet can be yellow-green, green, greenish brown,
orangy yellow, brown, grayish black or black. Melanite is a
black titanium bearing variety of andradite. Demantoid is a
rich green variety and Topazolite is the yellow variety and
is also occassionally cut as a gem.
- Uvarovite, Ca3Cr2(SiO4)3,
Calcium Chromium Silicate is the only consistently green
garnet and has a beautiful emerald-green color. As with the
other calcium garnets (andradite and grossular), Uvarovite
is formed from the metamorphism of impure siliceous
limestones and some other rocks that contain chromium.
Mineral specimens of Uvarovite are much sought after by
collectors for outstanding brilliance and color.
- A few garnets exhibit a color-change phenomenon and
exhibit an "alexandrite-like" effect. They are one color
when viewed in natural light and another color when viewed
in incandescent light.
Legends, Myths and Healing
Properties:
 Garnet's
powers include healing, strength, and protection. Legends dating
from the Middle Ages suggest that primitive cultures thought red
gems would stop bleeding. Garnets were believed to protect one
from poisons and cure other sicknesses including those dealing
with blood and infection and it is often worn to relieve
inflammations of the skin. It is also believed to regulate the
heart and blood flow and aid in curing depression. They were
believed to have the powers to smooth discord between enemies
and to prevent bloodshed. Garnet is considered the gem of faith
and truth. In earlier times, garnets were exchanged as gifts
between friends to demonstrate their affection for each other
and to insure that they meet again. Garnet jewelry has been
found that dates back to the Bronze Age (3000 BC). It is
believed that garnet was buried within the tombs of the dead to
offer protection through the death experience. Present day
therapeutic beliefs include: Rhodonite, emotional support, helps
one take the next step emotionally. |
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