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.
The word "rainbow" is used figuratively to describe tourmaline. In reality, it is a well recognized fact that tourmaline's diversity in color is not limited to the seven colors of the rainbow. Tourmaline can be colorless to just about any color, hue, or tone known to man. And if range of colors among different tourmalines is not enough, individual crystals can vary in color along their length or in cross-section.
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.
California.--Tourmaline was, until recently, the single largest contributor to the value of gemstones produced from California. And for the past 5 years, California has ranked as high as second and as low as sixth in the value of natural gemstone produced in the United States. The State's fabulous tourmalines were discovered by the gemstone industry in the late 1870's or early 1880's. The caveat, discovery by the gemstone industry, is used because Native Americans discovered and used these beautiful tourmalines long before that.
Since their discovery, the tourmaline deposits in Riverside and San Diego Counties have had more tourmaline produced and of greater value than any other deposits in the Northern Hemisphere. In fact, it is probable that only the deposits in Brazil have been more productive.
One of the reasons for the productivity of the area is the longevity of the individual mines. Many of them have operated intermittently from the 1890's until the present. The famous Himalaya Mine is quite likely the best example.
Records indicate that from 1898 until 1914, the Himalaya was the world's largest producer of tourmaline. Furthermore, the records indicate that in 1904 production from the mine was at least 5.5 metric tons. In 1989, 84 years later, a single pocket in the mine produced more than 0.5 metric ton of tourmaline.
The history of production from the mine is not one of steady continuous operation. The mine operated continuously from 1898 until 1914, after which it operated sporadically until 1952. At this time, it once again began continuous operations that lasted until 1964 when it returned to intermittent operation until 1977. Since then the mine has been in operation under the direction of Pala International.
California tourmalines come in all colors except certain shades of blue and yellow. They also occur in bicolors, tricolors, and concentrically and laterally zoned combinations. Crystals vary in diameter from about 3 millimeters to as much as 125 millimeters, and vary in length from about 12 millimeters to as much as 250 millimeters.
Because of the large size of the crystals available, some large stones have been cut from California tourmaline. A 400-carat pink-red stone has been cut, as well as a flawless 75 carat green to pink bicolor and flawless 30- to 40 carat green to colorless to pink tricolored stones.
California deposits should continue to produce quantities of faceting, carving, and cabochon grade, as well as specimen-grade tourmalines for some time into the future. In late 1992, a new deposit of tourmaline was discovered in Riverside County that could result in greater production over even a longer period of time.
Maine.--Tourmaline was the first gemstone mined in the United States by miners other than prehistoric man or Native Americans. Tourmaline mining began at Mount Mica, ME, in 1822 and, with starts and stops, has continued to the present. In 1992, operations at Mount Mica produced both gem-quality and mineral specimen tourmaline.
Figure 11.--Tourmaline from Maine.
(Photo is courtesy of Smithsonian.)
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 reported crystal from the site apparently is one that is 39.4 centimeters long, 17.8 centimeters wide, and weighs about 14.3 kilograms. Apparently, a flawless, blue-green 256-carat stone is the largest cut stone from Mount Mica.
Mount Mica may have been the first tourmaline producer in Maine, but it is by no means the largest. Newry Hill, a spur off Plumbago Mountain, or more specifically 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 mines ability to yield large quantities of quality tourmaline was clearly demonstrated by Plumbago Mining Corp. The company reported that from October 1972 until the Fall of 1974, it produced more than one metric ton of fine-quality tourmaline.
Other mines and quarries in a three county area produce gem- and specimen-grade tourmalines. The level and type of activities at each mine or quarry vary from year to year. Currently, most of them are open to hobbyist or professional collectors for a fee or with the owners permission.
Maine tourmalines come in a wide variation of colors, deep grass green to light green to
yellow-green to blue green. They are also found in all shades of red, from pink to deep red, and
blue-green to light blue to deep blue, and as colorless crystals. The State's mines also produce
bicolors and watermelon crystals. The colors can be very fine and some believe that Maine
tourmalines set the standard for non-chrome green tourmaline.
U.S. Department of the Interior
U.S. Geological Survey
988 National Center
Reston, VA 20192 USA
Maintained by: email@example.com
Last modification: 11-Jan-2013@16:56