from
DeKalb through all the shades of brown to the black variety found in
Pierrepont. On the other hand, the lithia tourmaline, containing more
or less manganese, gives us the red, green, blue, and colorless
varieties. The shades of color do not appear to depend on the absolute
amount of manganese present, but rather on the ratios existing between
that element and iron. When the ratio of manganese is to iron as one is
to one, there is produced the colorless, pink, or very pale green
tourmaline. An excess of manganese produces the red varieties, while if
the iron be in excess, the result is various shades of green and blue.
The finest green and red specimens are found in the province of Minas
Geraes, Brazil, the deep red rubellite in Siberia, the yellow and brown
in Ceylon, and Carinthia, Austria, and pink on the island of Elba. The
hardness of the flawless variety is about 7.5, and the specific gravity
varies from 3.0 to 3.25. It is very electric. The colorless variety is
called achroite, the red, rubellite, the blue, indicolite, the green,
Brazilian emerald, and the black, schorl.
Tourmaline
is one of the most dichroitic of all gems. When a crystal is viewed
through the side, it is transparent green, but when viewed through the
end of the prism, it is either opaque or yellow-green. For instance, in
tourmaline from Paris, Me., if two gems are taken from a green crystal,
one with the top cut from the side of the prism and the other from the
pyramid side, one will be bright green and the other yellow-green. It
has frequently happened with specimens from Brazil that one would be
green and the other opaque. Specimens that rival any found in the world
have been obtained in Maine. The localities that have furnished fine
ones are Mount Mica, near Paris, Auburn, Hebron, Norway, Mount Black,
in Andover, Rumford, and Stan-dish. In the two latter places, however,
they do not count as gems. The famous tourmaline locality at Paris,
Me., is situated on Mount Mica, a spur of Streaked Mountain, about one
mile east of Paris Court House. It was discovered in 1820 by Elijah L.
Hamlin and Ezekiel Holmes, while they were on a mineralogical and
geological trip. Mr. Hamlin found a fragment of a transparent crystal
lying loose upon some earth which still clung to the foot of a fallen
tree, and procured about thirty beautiful crystals.
