Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/169

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JARGOON.—TOURMALINE.
133

A century ago this gem was considered to be a variety of diamond; it was usually set in rings, buckles, and around stones of little value: at present it is seldom used in jewellery, and therefore bears but a very low price.


TOURMALINE.

Tuts stone is remarkable for its electrical properties. It generally occurs in black and opaque crystals; but the precious varieties are translucent, and of a green, blue, or pink color; they are used for ring-stones, brooches, or seals. By heat or friction it becomes elec tric, and may be distinguished by this property, which it retains many hours.