Tourmaline
Tourmaline is a group of mineral species that is so complex they are grouped as a single species by gemologists.  Their wide spectrum of color is produced by different trace chemicals and their species designations apply more to mineralogy than gemology.  The color range of Tourmaline is perhaps the greatest in the gem kingdom.
 
Colors and Origins  
Green is the color that initially comes to the minds of most Tourmaline aficionados.  Characteristically, green Tourmaline can occur in many variations, from the grayish- to yellowish-green of the famous California Himalaya Mine, to the bluish-green from the Maine deposits--incidentally, the first Tourmaline mines discovered in America.  These green Tourmalines are usually flawless or, at most, very slightly included.  A deep and pure green chrome Tourmalines originates from Africa.  Very rarely this African chrome Tourmalines produces change-of-color material that switches from chrome green in fluorescent light or daylight to deep red when viewed through transmitted light.  California’s Stewart Lithia Mine produces a characteristic “bubble gum” pink color peculiar to that locality; this color is a favorite of many mineral collectors because the rough specimens can be quite beautiful on their own, and the cut stones are very bright in hue.  The much rarer red or Rubellite Tourmaline comes mainly from Brazil, alongside more extensive pink Tourmaline deposits.
 
In addition, Tourmaline can display from two to five colors in a single crystal, and sometimes in characteristic patterns, such as “Watermelon” Tourmaline, a gem with a pink center surrounded by green or vice versa.  Tourmaline also occurs with aligned hollow tubes that create a cat’s eye effect when cut as a cabochon.  Although in modern times most Tourmalines are described by using a color to prefix the name (e.g. “Green Tourmaline”), older varietal names (Rubellite, Indicolite) exist and are listed below (at the Tourmaline properties).  These varietal names are no longer in common use.
 
Paraiba Tourmaline 
The new kid on the block, Paraiba Tourmaline, displays neon blue, green and violet hues in remarkable intensities.  The term “Paraiba” pertains to the locality where these special vividly colored gems first were discovered in 1987 in Brazil.  In the 1990s, larger deposits of similarly colored Tourmalines were discovered in Mozambique and Nigeria in Africa.  Today, unless the locality is documented, these specially colored Tourmalines are labeled “cuprian” or “Paraiba-like” Tourmaline. 
 
Formations & Mines 
Primary gem Tourmaline deposits occur in singular geologic formations called pegmatites.  In these pegmatites, pockets of air form and create a type of oven in which the Tourmaline crystals form.  Tourmaline crystals tend to form long thin crystals called “pencils.”  Because of the shape of these crystals, elongated rectangle step cut stones are often cut from the crystals to display the optimal color and to use as much of the crystal as is efficiently possible.  Tourmaline is most frequently mined in Brazil, Mozambique, Madagascar, Sri Lanka, and in the U.S. (specifically, California and Maine).
 
One of the most spectacular gem deposits was found in 1978 in the Itatiaia region of Brazil.  Magnificent cranberry red crystals, some of which were nearly 4 feet long and 16 inches in diameter, and weighing 100 kilograms, were pulled from the Jonas Mine and supplied gem cutters with more than 3.6 tons of cutting material in total.  The largest known single faceted Tourmaline is a slightly included 509 carat dark pink gem mined at the Tourmaline Queen Mine near Pala, San Diego County, California.
 
Famous Tourmaline Jewelry 
A famous piece of Tourmaline jewelry is the Hamlin Tourmaline necklace.  Consisting of 18 faceted Tourmalines of different colors, extracted from the Mount Mica mine located near Newry, Maine, the stones vary in size from 3 to 30 carats and the necklace is centered with a 34.25 carat green square cushion cut stone.  This center stone was mined in 1886 by Augustus Hamlin, son of one of the original discoverers of the mine.  A prominent family in American politics, Hamlin served as the mayor of Bangor, Maine, and his uncle, Hannibal Hamlin, served as vice-president under Abraham Lincoln.  The necklace was donated by Augustus Hamlin to the Harvard Museum in 1892, and it remains there to this day.
 
The hardness of Tourmaline enables it to be worn confidently without undue worry concerning scratches or breakage.  Tourmaline should not be steam-cleaned or put into an ultra-sonic cleaner; it is best cleaned with warm soapy water and a small brush.
 
Tourmaline properties
Species:  Tourmaline
Varieties:  Chrome (fine intense green), Rubellite (dark pink to red), Cats’ Eye Tourmaline, Paraiba, Cuprian, Color Change, Watermelon (pink center with green periphery), Verdelite (yellowish-green to bluish-green), Indicolite (violetish- to greenish-blue), Dravite (brown), Schorl (black), Achroite (colorless), Parti-Color (more than one color), Tsilaisite (bright greenish-yellow).
Chemical composition:  (Ca, K, Na)(Al, Fe, Li, Mg, Mn)3(Al, Cr, Fe,
V)6(BO3)3Si6O18(OH, F)4
Color:  Colorless, Brown, Black, Yellow, Green, Blue, Violet, Red, Pink, Orange.
Hardness:  7 - 7½
Crystal System:  Hexagonal
Refractive Index:  1.624 - 1.644 (+.011/-.009)
Specific Gravity:  3.06

Image by Paul Wild.
ADVERTISEMENT
image
ADVERTISEMENT
image
ADVERTISEMENT
image
v.2.0.0.1
The contents of the site are owned by The Net2 Group Inc. and may not be copied in any medium (including via caching), shared, or used for any purpose without its express written permission.
Copyright 2012 The Net2 Group Inc. All rights reserved.