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368 THE DIAMOND
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claimed
that the form of the carbon depends upon the amount of pressure
existing at the temperature which permits transformation.
Some
argue that these explosions are due to gas held under great pressure in
the interior of the crystal. Mr. Williams declares that to be an
argument against the theory of formation in an igneous magma at high
temperature. Broken diamonds are frequently found in the
diamondiferous pipes of South Africa. Though the cause of the fracture
is unknown, it has been ascribed to the volcanic action by which the
diamond-bearing clay was forced through intervening strata to the
surface.
Many
theories have been advanced as to the source from which Nature obtained
the carbon. Newton and later eminent scientists believed it to be of
vegetable origin, some basing their conclusions mainly on the
microscopic study of the residual ash. Crookes on the other hand
asserts that iron is the chief constituent of the ash, and uses that as
an argument in favor of deep-seated masses of molten iron saturated
with carbon, a larger process of the method employed in the laboratory
by himself and Moissan. In opposition to this Mr. Williams states that
many exhaustive tests which he has made with all kinds of diamonds for
iron, metallic or oxidized, with powerful magnetic apparatus, indicated
either an entire absence of iron, or infinitesimal traces only.
Inasmuch, however, as the crystallization appears to depend largely on
the complete segregation of the carbon from that with which it was
previously combined, this argument against the theory of Crookes does
not appear forcible. As science has made diamonds from saturated molten
iron, Nature may certainly have used
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