Jewelry Lovers

ALL stages of imaginable color possibilities are captured by this gemstone which, in addition to white and black, embraces every hue to be found in the spectrum, not only in pure tones but in all the fine nuances of innumerable shades, transitions, and mixtures. Should a collector set himself the task of amassing all the colorings of tourmaline, he would find a lifetime insufficient to incorporate the thousands upon thousands of ever differently tinted specimens into his collection.

Mixed colors are an innate feature peculiar to tourmaline. Because of its moderate refractive index (1.64), it eschews striking brilliance in favor of a modest restraint and comforting tranquillity. It contents itself with a soft, mellow, one might almost say tender luster, which in a single stone harmonizes into a lovely color symphony of manifold tones. In this multicoloration, tourmaline displays in masterly fashion the distinctive characteristic of pleochroism (differential selective absorption), which results from the property of absorbing incident light differently in different directions. Through this peculiarity, one and the same individual stone may appear in more than one distinct color. In tourmaline this phenomenon is caused by an interchangeability between divalent and trivalent iron.

But there is no end to the magic of this truly astonishing family of stones; there is still another inherent oddity to be appreciated. Crystallizing trigonally and thus developing three-sided prisms with often very beautiful terminations, tourmaline exhibits within one individual crystal, contrasting colors which once again describe a wide arc from the lightest to the darkest shades. At one end of the crystal we may, for example, find ruby-red rubellite, at the other end sapphire-blue indicolite, and in between, all conceivable notes are sounded from orange, through brown and yellow, to green. The yellow and brown tourmaline colors are caused by trivalent iron, that of the blue by divalent iron.

Wherever magnesium displaces the iron the shades become lighter. Manganese ripens into pink to red colorings; the drowsy hue of green tourmaline, resembling that of magnolia leaves, emanates from chromium or vanadium.

The degree of hardness (7.5) and the specific gravity (3.05) favor the recovery of tourmaline wherever it occurs, be it in Africa, Burma, Ceylon, California, or Madagascar. In Brazil, the most important treasure house of tourmaline, it is found in all colors mentioned above; moreover, these are not even scattered through the country but often concentrated in a single pegmatite vein, even in a single crystal. As a complex borosilicate, tourmaline is a typical representative of the plutonic rocks, in which are stored the volatile materials vital to its formation.

However, only the black tourmalines originate from pegmatitic melts; the gem qualities are of hydrothermal origin. Its matrix today is an extensively weathered rock which can be very easily broken up. The mining methods in Brazil are therefore of the greatest simplicity. Equipped only with pick and shovel, hundreds and sometimes thousands of itinerant prospectors, called garimpeiros, mark out a small claim on the gemmiferous terrain and dig either a shaft or a tunnel according to the nature of the deposit. As soon as the gem cavity or the concentration in the gravel is reached, it is more or less completely exploited. If unworked ground still remains in the neighborhood, the garimpeiros take out a new mining license in order to try their luck for the varicolored stones on this as well. Were it not for the abundant cheap labor, Brazil could never be the generous and important producer of gemstones that it is.

The unsurpassed color magic of the turamali, as the Sinhalese used to call all brown gemstones occurring in Ceylon, first became known in Holland in the year i 703 as the “ash magnet,” so called from its capacity to become electrically polarized when heated and to attract ashes as well as dust particles. The Dutch used it to draw the ash out of their meerschaum pipes. Those born inOctober rejoice in the bountiful colors of tourmaline, which—as the Muses’ stone—is said to speed the flow of thought.

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