28 Nisan 2013 Pazar

Maine State Mineral

Maine State Mineral


Tourmaline is a crystal silicate mineral compounded with elements such as aluminum, iron, magnesium, sodium, lithium, or potassium. A semi-precious stone, tourmaline seems to have a special place in the hearts of mineral collectors as well as in that of gem and gemstone enthusiasts. Its nearly universal popularity is based on two very important facts: first, it is a bright and beautiful gemstone that can be found in just about any color; and second, materials that are of acceptable quality are affordable to most purchasers.
Tourmaline can be colorless to just about any hue or tone known to man. And as if range of colors among different tourmalines were not enough, individual crystals can vary in color along their length or in cross-section. Tourmalines occur in black, brown, green, red, blue, yellow, pink, purple, and rarely orange, white, or colorless. Crystals frequently contain two or more colors. Some specimens are pleochroic, meaning they exhibit two or more separate colors and change intensity when viewed at different angles. Some change color when viewed in daylight versus artificial light.
The variations in color along a crystal's length give rise to the bicolor and tricolor tourmalines, which have multitudes of color combinations. The variation in color in cross-section can be concentric, as in the case of 'watermelon' tourmaline, a pink core surrounded by a green "rind." Or the variation may have a distinct triangular pattern as in the case of liddicoatite.
The more common varieties of tourmaline are schorls, which are black; dravites, which are yellowish-brown to dark brown; and the elbaite species. Tourmalines colored green from tiny traces of chrome are called verdelites, intense red tourmalines are called rubellites, and blue tourmalines are known as indigolites. The highly prized gemstones of intense blue to blue-green color from the Brazilian state of Paraíba are called paraíba tourmalines.
One of the most beautiful minerals found in Maine, tourmaline was designated the official state mineral in 1971. The gem was first discovered in the state in 1820 at Mount Mica in Paris, Maine. The quarry that was opened at the site continues to produce fine specimens today. Over the years, mining operations on Mount Mica produced hundreds of kilograms of tourmaline. Museums and private collections around the world contain outstanding examples of tourmaline from the deposit. The largest cut stone from Mount Mica is a flawless, blue-green 256-carat tourmaline, the national record for this gem.
Mount Mica may have been the first tourmaline producer in Maine, but it is by no means the largest. The Dunton Mine on Newry Hill is the most prolific tourmaline producer in Maine. Since its discovery in 1898, production from the mine has exceeded thousands of kilograms of high-quality tourmaline. The company reported that from October 1972 until the fall of 1974, it produced more than one metric ton of fine-quality tourmaline.
The Hamlin Necklace, which contains fine tourmalines of various colors from the Mount Mica quarry, is named for Maine mining pioneers and is on display at the Harvard University Mineralogical Museum. A 10-inch specimen nicknamed the Jolly Green Giant was mined from the Dunton Mine in Newry, Maine, and now forms part of the gem collection of the National Museum of Natural History in Washington, D.C. The Peary Necklace and one of the largest crystals from Newry, as well as other tourmaline specimens from Maine, are on display at the Maine State Museum in Augusta.
The word tourmaline comes from the Sinhalese words tura mali, which means something like 'stone mixed with colors,' and was the name given to colored gem zircons on the island of Sri Lanka. Because tourmaline occurs in more colors and color combinations than any other gemstone, it can easily be mistaken for other gems. The Dutch East India Company transported large amounts of these stones to Europe. In the early 1800s, it was discovered that some of these 'zircons' were actually new minerals. Many gems in the 17th century Russian Crown Jewel collection were once thought to be rubies, but are actually tourmalines.
Tourmaline occurs in igneous rocks such as granite and granite pegmatite, and in metamorphic rocks such as schist and marble. Schorl specimens are usually found in granite and granite pegmatite. Dravites generally occur in schist and marble.
  • United States: Pala area and Little Three Mine, San Diego County, California; Newry (Mount Mica area), Oxford County, Maine
  • Brazil: Minas Gerais
  • Sri Lanka
  • Russia
  • Myanmar
  • Afghanistan
  • Pakistan
  • Nepal
  • Namibia
  • Nigeria
  • Tanzania
  • Kenya
  • Mozambique
  • Malawi
  • Mexico: Alamos, Baja California
Other varieties of tourmaline are found in various other locations around the world. For example, elbaite is named for the island of Elba, Italy. Many fine specimens have been found in Elba, including the Mohrenkopf or Moor's Head variety, which are transparent stones with black tops that resemble a German confection.
Enormous dravite crystals have been found in Yinniethara, Western Australia. Excellent dravite and schorl specimens have come from DeKalb, Pierrepont, and Gouverner, in St. Lawrence County, New York. The rare uvite variety of tourmaline has been found in Gouverner, St. Lawrence County, New York, and in Ogdensburg and Hamburg, Sussex County, New Jersey. The best liddicoatite crystals come from the town of Alakamisy Itenina in Fianarantsoa province, Madagascar. The rare variety Buergerite comes from San Luis San Luis Potosí, Mexico.
Tourmaline is both pyroelectric, meaning it generates electricity under a temperature change, and piezoelectric, which means it will generate electricity under stress. This makes it an important component of high-pressure gauges. When the electrical charge changes, the stone begins to oscillate. In the 18th and 19th centuries, these properties were recognized and put to practical use by the Dutch, who were the first to bring the gem to Europe. They used tourmaline to clean ash and dust from tobacco pipes, and therefore the stone was known in the Netherlands as aschentrekker("ash puller").
Some tourmaline gems, especially pink to red colored stones, are altered by irradiation to improve their color. Irradiation is almost impossible to detect in tourmalines and does not impact the value. Heavily included tourmalines are sometimes clarity enhanced. A clarity-enhanced tourmaline is worth much less than a non-treated gem.
Tourmaline specimens are cut into gems and cabochons, sliced into cross-sections, carved into figurines, and kept in their natural state for collectors.
American gemologist George Frederick Kunz got his start collecting gem specimens and educating himself about gems and minerals as a child. At the age of 20, he sold the first semi-precious gems to Tiffany & Co. in New York, beginning with green tourmaline. Previously, Tiffany's had only sold the precious stones diamonds, rubies, sapphires, and emeralds.
Kunz went on to become Tiffany's resident gem expert, one of the founders of the New York Mineralogical Club, honorary curator of precious stones at the American Museum of Natural History, and author of several important articles and books on gemstones. He amassed several of the greatest gemstone collections in the world, which reside in museums today.
In 1912, the American National Association of Jewelers adopted tourmaline as the birthstone for October. It is also the stone for the zodiac sign of Leo and the accepted gem for the eighth wedding anniversary.
Ancient legend says that tourmaline is found in all colors because it traveled along a rainbow on its journey from the center of the earth, gathering all the rainbow's colors along the way.
Tourmaline is said to be the gem of love and friendship and is believed to strengthen both. Tourmaline is also thought to strengthen the body and spirit, especially the nervous system, blood, and lymphs. Because tourmaline is also thought to inspire creativity, artists and writers used the stone as a talisman.
State Mineral
Green Tourmaline Crystals
State Mineral
Bi-colored Tourmaline Crystal
State Mineral
Tri-color Crystals on Quartz
State Mineral
Polished Tourmaline Showing Range of Colors
Group: Silicate 
Chemical Formula: (Na,Ca) (Mg,Li,Al,Fe2+,Fe3+)3  (Al,Mg,Cr)6 B3 Si6 (OH,O,F)4
Crystal Structure: Trigonal
Hardness (Mohs): 7
Color: Green, red, blue, purple, pink, yellow, orange, brown, colorless, white, black. Very often multicolored, with a seemingly unlimited amount of color combinations.
Transparency: Transparent to opaque
Luster: Vitreous
Birefringence: ¦Ä = 0.0040–0.0070
Refractive Index: n¦Ø = 1.564–1.595,
n¦Å = 1.568–1.602
Density: Average 2.76
Streak: White
Cleavage: Imperfect on the [0001]
Fracture: Conchoidal
Some data courtesy of the Mineralogical Society of America
Author: World Trade Press

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