|
l82
|
GEMS AND PRECIOUS STONES IN THE
|
||
|
|
|||
|
and
Hall, found at Good Harbor Bay, Grand Marias, on Lake Superior, Mich.,
in the basalt, and as rolled pebbles on the beach, result from the
decomposition of the rock, the amygdules withstanding the action of
the weather better than the rock. They vary from the size of a pinhead
to over an inch in diameter. Many of the thomsonites are made up of
series of concentric layers of various shades of color, in soft tones
of flesh-red, creamy white, yellow, and green, and are excedingly
pretty, especially when polished, when they resemble the eye-agate.
Great numbers are annually sold to visitors at Lake Superior,
especially at Duluth, Minn., and Grand Marias, Mich. The cutting of
thomsonite consists almost entirely of a rounding off of the pebble, so
as to show the concentric and other markings to the
THOMSONITE
|
|||
|
|
|||
|
|
|||
|
|
|||
|
best
advantage. Some that have been polished are over an inch in diameter.
The small ones are generally of the finest material. Lintonite is
really a variety of prehnite, and takes a fine polish either alone or
when associated with the flesh-colored forms of thomsonite.
Natrolite
occurs in many localities in beautiful crystals, but too small to cut
for gems. Many veins of it, and one large area containing over 300
square feet of the mineral, were met with in the sinking of Shaft No. 2
of the West Shore Railroad, at Wee-hawken, N. J. Scarcely any of the
crystals were stout enough to afford gems. This beautiful, limpid white
mineral occurs abundantly all along Bergen Hill where tunnelling has
been carried on, and fine crystals have been found in the Lake Superior
copper region. None have been sold for gems in the United States,
although when suitable crystals are found, it is occasionally used for
the letter Ν in initial jewelry.
|
|||
|
|
|||