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TOURMALINE.
77

differently-coloured rays, not attainable by mere inspection of a polished slice of a tourmaline crystal:

COLOUR OF STONE. TWIN COLOURS.
Red Salmon—Rose pink.
Brownish red Columbine red—Umber brown.
Brown Orange brown—Greenish yellow.
Green Pistachio green—Bluish green.

A few illustrations of the influence of this powerful dichroism upon the appearance of cut and faceted tourmalines will be of service, not merely in identifying doubtful specimens, but in explaining the peculiar and exquisite quality of the colours which this gem-stone shows. If we cut a green tourmaline in such a manner that the table and culet are perpendicular to the axis of the crystal, the probability is that the gem will appear, especially in its thicker parts, perfectly opaque and black. Held sideways we may see some greenish and olive green hues, by looking across the stone from one part of the girdle to another. Now the same green tourmaline may be so cut as to present a brilliant appearance, with a fine play and interchange of two hues of green, by making the table parallel with the axis. If the crystal be a yellowish brown one, a very beautiful effect is secured by cutting it in the form of a brilliant, but with a small table parallel with the axis. The templets and other facets of the crown should be well developed so as to display, as the stone is viewed in different positions, the different colours of the light transmitted and reflected in different directions which become visible in one after another of the facets. If one of these be at one moment greenish yellow, presently it is yellowish brown, and then russet.[1] With pale yellowish and greenish grey tourmalines cut in a similar manner, there will be seen other and equally striking changes of hue.


  1. Frontispiece, Figs. 6 and 8.