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North
Carolina to the itacolumite of Brazil, in which diamonds are found, has
at times been urged as indicating that these may have been the source
of the diamonds, but no discovery of such stones has yet been made in
this formation. The diamonds of the Kettle moraine region of southern
Wisconsin have all been discovered since 1876. They have been obtained
at six localities in Wisconsin, and one locality each in Michigan and
Ohio. Seven good-sized diamonds have been found, the largest weighing
21-1/4 carats, and one locality has yielded numerous small stones. The
diamonds were obtained in gravels of glacial origin, and Hobbs has
shown, from a study of the directions of glacial movement, that the
original source of the getns may have been the territory lying
southwest and south of Hudson's Bay. The localities where the diamonds
were found, and the probable course of their distribution southward,
are shown on the accompanying map.
The
diamonds of California have been found in connection with gold-bearing
gravels, the gravels being sometimes those buried under lava flows. In
Amador, Butte, El Dorado, Nevada, and Trinity counties diamonds have
been found, the stones rarely exceeding two carats in weight, but being
generally of excellent quality. The accompanying minerals have been
zircon, topaz, quartz, epidote, pyrite, chromite, etc. The diamonds are
discovered in washing for gold; but the yield has never been sufficient
to repay search for them alone, nor is it likely ever to be. In one or
two localities in Oregon, Idaho, and Montana diamonds have been
similarly obtained.
Numerous
attempts have been made to produce the diamond artificially, some of
which have been attended with success, although no stones large enough
for industrial or ornamental use have yet been made.
Moissan,
of Paris, in 1893 succeeded in producing diamonds by heating iron
saturated with carbon to a high temperature, and then suddenly cooling
the exterior of the mass. This exterior cooling caused an intense
pressure on the interior, whence black diamonds of microscopic size
were produced as a result of the heat and pressure, as it is believed.
Still
more recently, von Hasslinger has obtained diamonds by fusing a mixture
corresponding in composition to the South African diamond-bearing
breccias. The diamonds were small, not exceeding .002 of an inch in
diameter, but they were colorless and transparent crystals. The success
of these experiments gives some reason to believe that fair-sized
diamonds may in time be produced artificially.
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