granite, gneiss, and pegmatite. Some of the corundum approaches the gem
variety, sapphire, in quality. A few clear blue stones have been found
and numerous bronze-colored fragments, some of which show a strong
chatoyancy when cut "en cabochon." The bedrock of this region is loose
shale and sandy shale which has been lightly folded. Some of it
contains quantities of sulphide concretions, pyrite or marcasite. This
shale probably belongs to the Mis-sissippian series which constitutes
the lower part of the Carboniferous.
gravel deposits of the creeks and streams in the areas mentioned are
composed of material entirely foreign to the bedrock of this part of
Indiana. They have resulted from the erosion of the glacial drift
deposits of the region, the materials of which are derived from far to
the north. Two areas of glacial drift have been mapped by Frank Leverett1 in
this part of Indiana, the older or pre-Wiscon-sin drift and the later
or Wisconsin drift. Mr. Leverett has kindly furnished the following
information: "The portions of Morgan and Brown counties in which gold
and diamonds are found are covered by pre-Wisconsin drift, the
Wisconsin drift lying north of these areas. In Morgan County Sycamore
Creek heads in Wisconsin drift and runs through an area of the earlier
drift. Highland and Cold creeks head in and flow through the
pre-Wisconsin drift only."
are reported to have been found associated with glacial drifts and at
several localities in Wisconsin, near Milford, Ohio, and near Dowagiac,
Mich. These finds have been summarized by W. H. Hobbs2 in a
discussion of the possibility of tracing back the route of the glacial
drift matrix to the original source of the diamonds. A comparison of
the weight, color, crystal form, and markings shows a wide variation in
the nature of the stones found. By plotting the diamond localities and
the glacial stria? recorded by the study of different geologists Hobbs
concludes that the source of the diamonds is far northward beyond the
Great Lakes in Canada.
concerning the finding of diamonds in Butte County, Cal., during 1912,
has been furnished by Messrs. Harry Jacoby and M. J. Cooney, of
Oroville, and D. L. Vinton, of Cherokee—all residents of that county.
Three diamonds were found during washing for gold in the placers of
Cherokee Flats. One stone found by John Hufford has been cut and is now
in the possession of R. S. Powers, of Oroville. This diamond weighed
1-1/6 carats before cutting and yielded a fine white flawless gem
weighing 17/32 carat.
L. M. Richard, of Stamford, Tex., has kindly furnished information
concerning a reported discovery of a diamond in Texas. The find was
made in June, 1911, by Elcy Black in loose sand and gravel in Foard
County, section 64, block 44. The specimen was reported by the Klein
Bros. Lapidary Co., of Chicago, 111., to be a rough diamond, rather
brown, but fairly clear, that would yield a cut gem
i Mon. U. S. Geol. Survey, vol. 38,1899.
2 Diamond field of the Great Lakes: Jour. Geology, vol. 7,1899, pp. 375-388.