The
strong dichroism of tourmaline should be borne in mind in cutting gems
from it. Since a crystal looked at in the direction of the vertical
axis is usually much less transparent and of less pleasing color than
when seen at right angles to this direction, gems should be cut with
the table parallel to the prism. They will then exhibit their most
pleasing color in the direction in which they are usually seen.
Of
the different colors of tourmaline used for gems, red shades are less
abundant, and more highly prized than green. Of the red tourmalines,
those dark red are most valued, especially if, as is sometimes the
case, a color like that of the ruby is exhibited. A rose-red color is,
however, more common. The green tourmalines are usually dark green,
shading to blue or yellow, and almost never exhibit the true
emerald-green. Blue tourmalines are least abundant of any, and are
rarely cut. Their color is usually an indigo-blue. Tourmaline is not
attacked by acids, and the transparent varieties are infusible. Partly
on account of its lack of strong color, and partly because it is not
better known, tourmaline has not hitherto obtained much popularity as a
gem, although its hardness, dichroism, and transparency are such as to
warrant its more extensive use.
Recently, however, it has obtained more favor, and the supply of Brazilian tourmalines especially is hardly equal to the demand.
One
of the best known localities for gem tourmalines is Paris, Maine. It
was discovered by two boys, by name Elijah L. Hamlin and Ezekiel
Holmes. They were interested in the study of minerals, and spent much
of their leisure time searching for them. One day in the fall of 1820,
having been out many hours hunting for minerals, they were about to
return home when a gleam of something green at the roots of a tree
caught their eye. Eagerly bringing it to light, they found it to be a
beautiful green tourmaline. A fall of snow that night prevented their
obtaining more of the crystals, but the following spring they returned
and secured many fine gems. The locality has been extensively worked
since then, and has furnished many fine gems, which have gone to adorn
the coronets of kings and enriched the mineral cabinets of the world.
The tourmaline occurs in pockets in pegmatitic granite. Black
tourmaline, muscovite, and lepidolite are of constant occurrence
through the granite. The granite is overlaid by mica schist, which at
present is being stripped off to permit of further mining. It is
estimated that fifty thousand dollars' worth of tourmalines have been
taken from this one locality. Auburn and Rumford, Maine, are two other
neighboring localities where good gems have been found. At Haddam
Neck, Connecticut, fine transparent tourmalines occur, generally green
in color, and many of them of gem quality. They occur in granite.
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