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UNITED STATES, CANADA AND MEXICO
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15
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morphosed
until the middle or later Mesozoic. From the general resemblance of
conditions above referred to, the details of discovery in the two
regions are remarkably similar, and in both occasional diamond
crystals are found, accidentally picked up on the surface, or more
frequently encountered in the search for gold, sometimes in
placer-mining and sometimes in the flumes and sluices of hydraulic
workings. They have sometimes been overlooked, unrecognized, or
destroyed by rude and ignorant methods of testing, and at other times
have been made the basis of fabulous estimates and exaggerated tales,
but they have not as yet been found in sufficient quantities to justify
an attempt at diamond-mining, nor have the specimens obtained been of
more than local interest and moderate value.
With
regard to the finding of diamonds in other parts of the country, there
have been various reports, but little or no positive evidence. The
supposed diamond field of central Kentucky has been the subject of much
interesting study and discussion on account of the striking
resemblance of the rock to that of the diam-antiferous region of South
Africa ; but the conditions are found, upon closer examination, to
present important differences, and the diamonds are yet to be
discovered. The formations in the eastern portions of the United States
where diamonds have been found are entirely different from those of
South Africa. They resemble more nearly those of the diamond fields of
Brazil and of parts of India. The diamonds found in the United States
are much older than those of South Africa, and if they have ever
occurred in rock similar to that in Kimberley, there is nothing to
indicate it now, since the rocks in American diamond-bearing localities
are mainly granitic. It may be said that, while diamonds are found to
some extent within the limits of the United States, there is no reason
as yet to believe that they will ever be numbered among our important
mineral products. Their local and scientific interest is of course
very great; and this fact will justify the somewhat detailed account
of their occurrence given in this volume as an important part of a work
on precious stones in the United States. Prof. H. Carvfll Lewis paid
much attention to this subject, visiting many of the localities where
diamonds had been found in the eastern part of the United States, and
personally in-
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