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PRECIOUS STONES.
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at
the head of Nicoamen River, Yale district, British Columbia. Morion
quartz, in some cases an inch or two thick, in the vicinity of Lake
Ramsay, Lunenburg County, Nova Scotia.
Vesuvianite, of a honey-yellow color, of fine gem quality, in the township of Harrington, Argenteuil County, Quebec.
Mr.
H. S. Williams, of New York, reports a production of sodalite in
British Columbia, from which locality 125 pounds were obtained by
himself and Mr. O. M. Harper.
GEM MINERALS OP MADAGASCAR.
A
report on the precious stones of Madagascar has been prepared by Albert
Dabren," mining engineer of the colony. The following is quoted from
the abstract of this report by W. T. Schaller:b
In
pegmatites traversing crystalline schists are found the following gem
minerals: Amethyst, zircon, sapphire, topaz, garnet, tourmaline, and
beryl, the last two being mined as gems. The variously colored
tourmalines—pink, green, blue, and colorless—are found in the
pegmatites, which consist of quartz, mica, orthoclase, micro-cline
(sometimes green), and albite. The associated minerals are lepidolite,
garnet, yellowish green and pink spodumene, and pink, yellow, green,
and pale-blue beryl. In some crystalline limestones are found green
spinel, reddish, bluish, and greenish corundum, white diopside, and
tremolite. In the important river alluviums occur corundum, spinel,
yellow transparent chrysoberyl, topaz, beryl, almandine garnet,
tourmaline, and quartz. Colored corundum is very abundant in certain
alluvium deposits, being found here with the other gems above
mentioned. These corundums have not as yet been found in place. They
seldom yield cut gems of over a carat weight. Abrasive corundum is also
found. Greenish blue kyanite is found in place in mica schist.
Colorless, yellow, brown, or pink zircons, not found in place, are very
abundant in the alluviums. They are too minute to be used in jewelry.
In 1906 the exportation of precious stones amounted to 29,716 grams, of
which 7,930 grams were tourmaline, 1,350 beryl, 1.135 garnet, and 1,000
rose quartz. The production of rough corundum from Analambato was
243,280 grams. The modes of occurrence, association, and especially the
localities for the various minerals named above are described very
fully in the paper.
RADIUM AND CORUNDUM.
The experiments performed by Mr. F. Bordas on the action of radium on sapphire gems are of interest.c It
was found that blue sapphire, exposed to radium bromide of 1,800,000
activity, changed to green, to yellow, and finally to dark yellow;
while red sapphire changed to violet, to blue-green, to yellow. Mr.
Bordas observes that the color is not destroyed by heat, though Mr.
George B. Selden, jr., of Rochester, N. Y., in repeating these
experiments d found that the yellow color was
quickly destroyed by heating the sapphire to 800°. It is not thought
these reactions will be commercially used, though they are
scientifically interesting.
PRODUCTION.
The
production of precious stones in the United States during 1907 as
reported to the Survey was much greater than during 1906. The values
given in some cases are those estimated for an output of a known
quantity of gems, and where possible the value of the rough material is
represented, in accordance with the aim of the Survey. It is often
impossible to obtain accurate figures in this form, since it
a The precious stones of Madagascar: Bull. 6conomique, *> trimestre, 1906. (Tananarive, Madagascar.)
t>Chem. Abstracts, vol. 2, No. 7, Apr. 10, 1908.
"Mining Jour., London, November 9,1907, and April 4,1908
^Jewelers' Circ. Weekly, February 12,1908.
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