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FIRE IN THE EARTH
for
a number of years and yielded a small number of gem diamonds, the
largest recovered weighing about 40 carats. In the summer of 1941 the
Arkansas Diamond Corporation sold its long-idle field to an anonymous
Chicago syndicate for $175,000. This field covers about 44 acres and
extends at least 200 feet underground, but the difficulty in operating
it may be laid to the cost—and also the possibility that the deep earth
holds little more than hope.
Diamonds
have been picked up in other parts of the country, including
Wisconsin, Michigan, Indiana, and Ohio, a few in California, Virginia,
and Georgia. But they have been so rare that they are considered freaks.
Yet,
when you think of it, it is strange that Nature wasn't more fluent with
her diamond-bearing igneous rocks. All rocks, after all, are a
hodgepodge combination of natural substances called minerals. Igneous
rocks, in general, are classified according to the amount of quartz
they contain. Blue ground, although a basic igneous rock, usually
contains no quartz and when that happens you are apt to find diamonds.
In the beginning this blue ground was composed of large amounts of
glassy, grass-green mineral (olivine) with smaller amounts of cores of
others, including gamet, bronze-colored mica, and dark, heavy iron
minerals. While this mass was cooling, the olivine was attacked by chemical solutions
and most of it turned into serpentine, a soft mineral, rather dark
greenish-blue, which accounts for the name "blue ground."
How
did the diamond come out of all that? In the opening chapter we dealt
only in generalities. The specific story is surprisingly interesting.
One of the best descriptions I've been able to find is in a pamphlet
issued by the Chicago Jewelers' Association in connection with the
Diamond Exhibit of the Chicago Century of Progress Exposition in 1933
(28)
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