The tourmaline or precious schorl is known under many different names, and no other mineral has such a suite of colors.

The colorless variety is known as achroite; the red, as rubellite or siberite; the blue, indicolite or Brazilian sapphire; the green, Brazilian emerald; and the yellowish-green, Ceylon chrysolite or Ceylon peridot. Besides the above colors and their shadings, the tourmaline occurs in black and brown. The crystallization is obtuse rhomboid, and generally forms six-, nine-, and twelve-sided prisms.

Some of the crystals are very large, specimens over eight inches long having been mined.

The tourmaline crystals are remarkable for their varied and beautiful groupings of colors. Some are internally blue or brown, surrounded by a bright carmine red or dull yellow; others are red internally and are enveloped by a green exterior; crystals are sometimes pink at the summit and light green at the base, or crimson tipped with black, or white at one end shading into green and finally into red at the other end. The hardness of the tourmaline is 7 to 7.5, specific gravity 3 to 3.1, and lustre vitreous.

The tourmaline becomes decidedly electric by heating or rubbing, and will readily attract small pieces of paper and other small objects. The rubellite or red tourmaline is composed of:

The green tourmaline is composed of

The tourmaline possesses double refraction to a high degree, and its power of polarizing light is so great that, cut into slices, it is used in the polariscope for analyzing other minerals.

If two slices of tourmaline, cut parallel to their axis, be laid one on the other in one direction, both are transparent; if laid in another direction they become opaque, and if a doubly refracting crystal be placed between the two plates of tourmaline, the part covered by the crystal is transparent while the other is opaque.

Tourmaline melts with borax into a transparent glass; the rubellite turns white, and the indicolite and green tourmalines turn black, under the blow-pipe.

Tourmalines can be distinguished from other gems by their specific gravity, but principally by their property of assuming polaric electricity after being heated, one end becoming positive and the other negative.

The history of the discovery of the tourmaline and its electric property is a curious one.

On a warm summer day, early in the eighteenth century, some children were playing in a courtyard in Amsterdam. Amongst their playthings were some precious stones which the Dutch navigators had brought from Ceylon. Some of the stones seemed to be possessed of the strange power of attracting and repelling small bits of straw, ashes, and other light substances. The little ones called their parents to witness this strange phenomenon, and the stolid Dutch lapidaries, themselves puzzled at the sight, called the stones aschentreckers or ash-drawers.

A number of years afterwards, careful experiments disclosed the wonderful electric powers of the aschentreckers or tourmalines. Purple, green, and blue tourmalines are found in Brazil. In Ceylon the stones are found in gravel beds. Rubellites or siberites are found in Siberia.

Tourmalines are also found in Moravia, the island of Elba, Sweden, Burmah, Tyrol, Canada, and the United States.

The first tourmaline deposits known in the United States were discovered at Paris, Maine, in 1820. Another wonderful deposit was found at Mt. Apatite in Maine in 1882, and up to the present time the finest tourmaline crystals have been discovered in the United States.

Really fine specimens of red, blue, or green tourmalines are uncommon and command very good prices.