Professional Jeweler Archive: Namibian Mint

August 2000

Gemstones & Pearls/News

Namibian Mint

A classic tourmaline mine prepares to reopen

Minty green is one color you don’t expect to see in the brown, arid Namib Desert in Namibia in southwestern Africa. But deep within pegmatite dikes under the barren landscape, nature has compensated.

Conditions here are right for the formation of luxurious green tourmalines in clear, finger-sized crystals and curious rounded formations called kugels (German for balls).

This 70-year-old source for blue-green tourmaline is a classic by any mine’s standard. “And it’s still going strong,” says Jim Alger of Alger & Co., a gemstone dealer in Bedford, NH. Alger recently visited the mine near Usakos, northwest of Namibia’s capital of Windhoek. In fact, a recently discovered pegmatite pocket caused temporary closure of the mine as a security precaution. The entire area is being prospected though, and the owner seems optimistic about several new finds. Alger says once the mine reopens later this year, good supplies of the green gem will reach the market once again.

Tin to Tourmaline

Meanwhile, the mine is for sale, stirring memories of its history. About 70 years ago, a tin miner waited to complete the sale of his tin mine near Usakos. The compulsive miner took one last go at the dynamite. The resulting blast uncovered a “vug,” or tourmaline pocket, that yielded a ton of the gem. The sale of the mine was off, at least temporarily, and the tourmaline search was on.

Two years later, Gebrüder Bank of Idar-Oberstein, Germany, a multigenerational cutting family, bought the mine. Sid Peters later held the mine before selling to David and Shelley Mansfield, owners of the nearby Neu Schwaben mine. Neu Schwaben produces similar-looking, large blue-green tourmaline.

The first mine produces about 700 kilograms of tourmaline annually.

Beauty of Usakos Tourmaline

Alger says much of the tourmaline from Usakos is “open axis,” meaning light splits and travels at about the same speed through the gem. (Tourmaline is doubly refractive, which means light splits into two directions upon entering the gem. Often in tourmaline, one direction of light is perceived as weak or dark. The other direction may exhibit a bright color. Green tourmalines are often cut to show their “best” color through the table facet.)

Tourmaline may be perceived green in one direction and blue, brown or black in another. So tourmalines that show lively colors in both directions – such as bright green in one and blue in another – are doubly prized and coveted.

Usakos tourmalines contain chromium, says Joel E. Arem, Ph.D., F.G.A., in his book, Color Encyclopedia of Gemstones (Van Nostrand Reinhold Co., New York City, 1977). Chromium is known as the cause of color in some of the finest green tourmalines.

The crystals from the mine near Usakos also lend themselves to spectacular gem cutting. The crystals tend to be large and relatively free of inclusions, allowing cutters to create fine, large faceted gems ranging from 3 to 10 carats.

  • James Alger Co., Bedford, NH; (603) 625-5947.

– by Robert Weldon, G.G.

Tourmalines from Usakos, Namibia, are mined in long, finger-sized crystals that lend themselves to large cut gems. Dichroism in the 11.60-ct. center gem accounts for the lively mix of blue and green. Courtesy of James Alger Co., Bedford, NH.
Some crystals from Usakos have a rounded, translucent appearance and bright, minty green color. Courtesy of James Alger Co., Bedford, NH.
The main pit at the Usakos tourmaline mine has been in operation for close to 70 years.

Copyright © 2001 by Bond Communications