DIAMOND.
A
small production of diamonds from Arkansas is reported. A number of
diamonds were found in 1916 by L. J. Wagner, the watchman at the
Arkansas mine owned by the Arkansas Diamond Co. The modern though small
washing plant of the Kimberlite Diamond Mining & Washing Go. on
the bank of Prairie Creek at Kimberley was operated almost continuously
in making further tests of the ground on the Mauney and Ozark mines and
in complying with the terms of the lease held by this company on the
Mauney mine. For a number of years neither of these companies has
reported to the United States Geological Survey a production of stones,
so that the values given in the table on page 889 under diamond, having
been moderately estimated, may be too small.
The
American mine, formerly owned by the American Diamond Mining Co. but
now owned by T. E. Flournoy, of Monroe, La., and the Kimberlite mine,,
owned by the Kimberlite Diamond Mining & Washing Co., were idle.
Neither was work done at the " Black Lick," where peridotite has been
found.
A report on the diamond-bearing areas of Arkansas is now in preparation by H. D. Miser, of the United States Geological Survey.
Isolated
diamonds continue to be found in Cherokee Flat, Butte County, Cal. The
weights of three such stones, reported as found in 1916, are 1.2, 0.73,
and 0.54 carats, respectively.
Another
diamond was found in Brown County, Ind., by J. W. Cornett, of
Martinsville, Ind., who reports that the stone was found in the gravel
of the bed of Lick Creek, about 15 miles southeast of Martinsville. The
associated minerals are gold, garnet, and corundum (sapphire and
ruby). Mr. Cornett kindly sent the stone to the United States
Geological Survey for examination.
The
diamond is fairly clear and decidedly yellowish in color. Its
dimensions are 4.5 by 6 by 7.5 millimeters. It weighs 0.2966 gram or
1.48 carats. Its density is about 3.54. It is a rounded
rhombic-dodecahedron, elongated slightly in the direction of an
octahedral axis. The crystal was originally bounded by 12 flat faces of
the dodecahedron but in its present form it is bounded by 24 curved
surfaces. This doubling of the number of faces is due to a peculiar
form of corrosion by which each flat dodecahedral face was replaced by
two curved faces. The boundary lines (on each originally flat
dodecahedron face) where two corrosion streams met, which are also the
line of contact of the two replacing faces, are, on the smaller
dodecahedral faces, fairly straight and symmetrical, but on some of
the larger and elongated dodecahedral faces the boundary lines are very
oblique and curved so that some of the original faces have been divided
into two very unequal parts. The crystal resembles very closely the one
from German Southwest Africa, described and illustrated by Fersmahn
and Goldschmidt1 in the atlas of their work en the diamond.
The
surfaces of the Indiana crystal are considerably pitted with small
markings, which appear to be irregular but which, observed under low
magnification, are readily seen to consist in part of paral-
1 Fersmann, A. V., and Goldschmidt, V., Der Diamont, pi. 30, fig. 207 (crystal 95), Heidelberg, 1911.
