Ch. 3: Precious Gem stones in 1912

Ch. 3: Precious Gem stones in 1912 Page of 93 Ch. 3: Precious Gem stones in 1912 Text size:minus plus Restore normal size   Mail page  Print this page
1040                              MINERAL RESOURCES, 1912.
garnetiferous 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.
The 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."
Diamonds 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.
Information 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.
Mr. 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.
Ch. 3: Precious Gem stones in 1912 Page of 93 Ch. 3: Precious Gem stones in 1912
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US Geol. Surv. 1912. Gemstones, Metals.
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