In October 2002, Tanzanite was added to the official birthstone
list by the American Gem Trade Association as an additional
birthstone for December. Tanzanite was first discovered in 1967
in Tanzania, East Africa. As one of the newest and most
exotically colored gemstones, Tanzanite is part of the Zoisite
mineral species. Tanzanite is a brittle stone and although it
can be worn daily, care should be taken to protect it from
knocks, pressure and extreme temperature changes. Do not use a
home ultrasonic to clean jewelry with Tanzanite. Tanzanite is
very rarely a pure blue and usually exhibits rich purple
overtones. Tanzanite is 6.5 - 7 on the Mohs scale of hardness.
The only known source of Tanzanite is a five square mile hilltop
at Merelani, ten miles south of the Kilimanjaro International
Airport in Tanzania.
Click here for a picture in natural form.
Click here for more faceted and natural specimens.
When first mined, most stones are a muted green color, often a
blue color and it can also be brown. Tanzanite is routinely heat
treated to permanently draw out its exotic bluish-purple color.
It has better fire than the Tourmaline elbaite or Peridot and an
adequate hardness. Its only one direction of cleavage is
somewhat of a problem because it is oriented with the direction
of strongest pleochroism. Pleochroism is very pronounced in
Tanzanite and is seen as three different color shades in the
same stone. In the viewing a tanzanite stone, the colors dark
blue, green-yellow and red-purple can be seen, all a result of
pleochroism. Lesser stones may have a brownish color due to the
mixing of blue, purple and green. This would be a problem in
most gemstones because that is the direction the gemcutter would
usually select to maximize the color. However, with tanzanite
the color is usually strong enough anyway.
Iolite is a blue-violet gemstone variety of the mineral
cordierite, has strong pleochroism and can be confused with
Tanzanite. However, Iolite is usually less strongly colored, its
pleochroic colors vary from blue-violet to yellowish gray to
blue and it has less fire. Iolite's unusual color shades makes
it an exotic colored gemstone whose popularity is growing day by
day. Tanzanite is named after the only location it is found, the
country of Tanzania.
The formula for Tanzanite is variety of Zoisite, Ca2Al3(SiO4)3(OH),
Calcium Aluminum Silicate Hydroxide. Zoisite, like all epidote
minerals, is a structurally complex mineral having both single
silicate tetrahedrons, SiO4, and double silicate
tetrahedrons, Si2O7. The formula of
Zoisite could be expressed in a such a way so as to reflect this
Zoisite has been known for nearly two centuries as as a
sometimes ornamental stone of limited distribution. Only in 1967
was the blue gemstone variety found in Tanzania. The variety was
a surprise to minerologists and gemologists alike in that it had
come from a very ungemstone-like mineral. The blue-lavender
color of Tanzanite is unique and sets it apart from the other
gemstones. Besides tanzanite, Zoisite has produced other
attractive specimens that are of interest to collectors. A pink
variety called Thulite is usually massive and used for beads and
cabochons. A brilliant green variety is associated with medium
grade Rubies and is quite popular as an ornamental stone. The
Red Rubies are often distorted and irregularly spread throughout
the sea of massive Green Zoisite. It is one of the most colorful
of ornamental stones and competes well with the popular pink
Tourmaline and lavender Lepidolite of California.
Legends, Myths and Healing
says that it was Masai cattle herders that first noticed this
stone some 30 years ago after a fire caused by lightening burned
areas in Tanzania. The herders noticed that brown zoiscite
crystals had turned a deep blue-purple due to the heat from the
fire. Because this is such a new gemstone, there is little
folklore or healing properties surrounding this stone.