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minerals-n-more.com
Mineral
Specimens, Gems, Jewelry & Gifts
CHEMISTRY Elbaite, Na(Li,Al)3Al6B3Si6O27(OH)3(OH,F)
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.603 - 1.655
HARDNESS 7 - 7.5
SPECIFIC GRAVITY 2.84 - 3.10
CLEAVAGE No
HEAT SENSITIVE Some
WEARABILITY Very Good
SPECIAL CARE INSTRUCTIONS
Multicolored gems are often weak
where the colors meet
ENHANCEMENTS Heat treatment,
common on dark gems, occasional.
Irradiation, occasional.
Tourmaline has more varied colors than any other gemstone. With more than
100 hues available. Tourmaline's almost limitless colors, can resemble
almost any other gemstone. Although red, green, and multicolored are its
most famous colors. Scientifically, tourmaline is not a single mineral,
but a group of minerals related in physical and chemical properties.
The mineral elbaite is a member of the tourmaline group responsible for
almost all the gem varieties. Although elbaite is a separate member of
the tourmaline group, and occurs in all different colors, the term elbaite
refers only to green tourmaline in the gem trade. The other color forms
of elbaite have their own variety names on the gem market.
There are three other members of the group. Dravite, Schorl, and Liddicoatite.
These varieties are seldom used as gems. Dravite is brown in color, and
is rarely transparent enough to be used as a gem. They can be heat-treated
to lighten their dark color and are sometimes cut into gems. Schorl, which
is dark gray to black, basically has no gem use. With the exception of
being used in it's natural crystal form. Liddicoatite is too rare to be
used extensively, although its popularity as a gemstone is increasing.
More rare members of this group are in the Silicates Class, under Cyclosilicates
Rubellite is the term used for red or pink tourmaline, and indicolite
is the term used for blue tourmaline. A recent trend in the gem market.
Is to call all tourmalines by the color designation as opposed to variety
name. For example "Rubellite" would be "red tourmaline"
Current Gem Trade Names:
Anchorite:
A Colorless variety of tourmaline
Bi-color:
Bi-color tourmalines are very unique. As there are no other gems that
resemble them. Only Ametrine, a Bi-color mixture of purple amethyst and
yellow citrine, comes close. But this gem has characteristic colors that
would not be confused with Bi-color tourmalines
Cat's Eye:
Are pink and green tourmalines from certain localities that contain tiny,
parallel inclusions, causing them to display a strong cat's eye effect
when polished. Such stones are usually cut as cabochons.
Chrome:
A rare type of tourmaline from Kenya, Zambia, Namibia and Tanzania. It
comes in very rich green colors. Caused by Chromium or Vanadium oxides.
Chromium is same element which causes the green in emerald. Chrome Tourmaline
was first mined in Tanzania in the 1960's. This Tourmaline can have the
color of top grade Emerald and is much more durable.
Dravite:
A brown variety of tourmaline
Elbaite:
(Green Tourmaline) This is the most recognized of the Tourmaline
colors. Green Tourmalines are typically eye clean stones. Most are cut
in rectangular shapes. Shades range from a pastel Green to a deep, vibrant
Green.
Indicolite:
The finest Blue Tourmalines are medium dark Blue, close to the color of
Blue Sapphire. Sources for Indicolite are Sri Lanka, Brazil, Madagascar,
California and Maine. Indicolite is typically a clean Gemstone, seldom
with eye visible inclusions
Orange & Yellow:
These colors don't seem to have any real well known commercial names.
But Tourmaline does come in these colors and many shades in between.
Paraiba:
Or Neon Tourmaline. First called "Electric" then "NEON." This gemstone
was discovered in 1989. It's brilliant blues and greens are the most vivid
ever seen. It is the only Tourmaline in the world that contains Copper.
A recent study by the German Foundation for Gemstone Research also discovered
a surprisingly high gold content, 8.6 parts per million. The term "NEON"
defiantly describes the colors of this gem. It's only location is near
the village Sao Jose de Batalha. In the state of Paraiba, Brazil. The
mine shafts are deep, hand-excavated tunnels, with very thin veins. This
means the supply will always be limited, rare and expensive.
Pink:
Pink Tourmaline has become a favorite for mounting because it is available
in so many shades, ranging from light pink to hot pink and many shades
in between. Gemologists think that natural irradiation produces the Pink,
Red and Violet colors in Tourmaline. To get the color of the very hot
pinks. You can expect it to be Cobalt treated.
Rubellite:
Called Rubellite because the deepest shades appear Ruby Red. The darker
reddish colors tend to have more natural inclusions than the other Tourmaline
colors because they are formed near the center of the crystal pocket and
receive more stress and pressure during formation. Eye clean Rubellite
is one of the most expensive of the Tourmalines. Since most Rubellite
has visible inclusions. Clean Rubellite is very rare, so if you see a
super clean stone it's probably a radiated Pink Tourmaline or a Rhodalite
Garnet.
Schorl:
black variety of tourmaline
Watermelon:
Or Tri-color are Green and Red with a White separation. The vast majority
of the stones are obscure or heavily included. Clean Gems are much more
expensive. Definitely one-of-a-kind Gems. Watermelon Tourmaline is a highly
valued Collectors Gemstone.
General Information:
Almost every color of tourmaline can be found in Brazil, especially in
Minas Gerais and Bahia. Pink and green colors are particularly popular.
In addition to Brazil, tourmaline is also mined in Tanzania, Kenya, Madagascar,
Mozambique, Namibia, Afghanistan, Pakistan, Sri Lanka, and California
and Maine in the United States. Maine produces beautiful sherbet colors
of tourmaline and spectacular mint greens. California is known for perfect
pinks, as well as beautiful bicolor.
Tourmalines are most often, pencil thin. Because of this long narrow crystal
shape.Tourmaline is often cut in long rectangular shapes. This long narrow
cut has been called "Tourmaline Cut" More and more, the Crystals
them selves are being set in jewelry.
Tourmaline crystals are often cracked and flawed, especially in the Red,
Pink and BI-colors. Clean stones of 10 Carats or more in these colors
command a premium price. The Green and Blue colors are generally very
clean.
Tourmaline exhibits the interesting electrical properties of pyroelectricity
and piezoelectricity. When heated or rubbed, it attracts dust and dirt
particles. This is caused by its atomic structure, which causes it to
generate an electrical charge when heated or rubbed.
The vivid colors like Bubble Gum Pink in Tourmaline is Heat or Cobalt
Irradiation treated. To enhance and stabilize the color. Heat Treatment
can enhance the color of some tourmalines. Some greenish stones can be
made deep green, some reddish brown stones can be made red, and some light
pink stones can be made colorless. Some lighter colored stones can also
be made into a deeper hue, and dark, transparent Dravite can be made lighter.
All colored tourmaline gems display pleochroism, meaning their color changes
when viewed at different angles. In some gems, this effect is hardly noticeable,
while in others it is strongly apparent. Gemstone cutters must take this
into account when cutting a tourmaline, so the finished gem brings out
its best color.
CARE:
Tourmaline is a very good choice for jewelry. But the more rare and expensive
stones should be treated with respect. It is a relatively hard stone.
But it is only a little harder than Quartz. So sharp quartz sands in your
gardening or whatever. With a little pressure can scratch your beautiful
expensive Tourmaline. Jewelry made with Tourmaline should not be cleaned
in an ultrasonic or steam cleaner. We recommend ionic cleaners and/or
warm, soapy water and a soft brush as the best way to clean Tourmaline.
Some Tourmaline Lore:
Its name comes from the Sinhalese word "turmali" meaning
mixed. Bright rainbow collections of gemstone varieties were called
"turmali" parcels. Due to the tendency to confuse Tourmalines with other
Gems. Tourmaline lives up to its name. Perhaps this is why this gemstone
is said to encourage artistic intuition. It has many faces and expresses
every mood.
Tourmaline from Sri Lanka (formerly Ceylon) was first introduced to the
Europeans in the late 1600's or early 1700's by Dutch traders. Many stones
in the Russian Crown jewels from the 17th Century once thought to be rubies
are actually tourmalines.
The Empress Dowager Tz'u Hsi, the last Empress of China, loved pink tourmaline.
She bought almost a ton of it from the Himalaya Mine in California. This
mine was located a long way from the Mother Country . The Himalaya Mine
is still producing tourmaline today but the Dowager went to rest eternally
on a carved tourmaline pillow.
Tourmaline is also of interest to scientists because it changes its electrical
charge when heated. It becomes a polarized crystalline magnet and can
attract light objects. This property was noticed long ago before science
could explain it. Many years ago in the Netherlands. Tourmalines were
called "aschentrekkers" because they attracted ashes and could be used
to clean pipes!
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