fivecounties, Amador, Butte, El Dorado, Nevada, and Trinity are known to have yielded them. Other localities and larger numbers are yet, in his judgment, to be discovered.
A few small diamonds have been found in the placer diggings of Idaho, of about the same quality, and occurring under the same condi' tions as those in California. Some excitement has occasionally arisen about these Idaho diamonds. In 1864 to 1866 local and mining papers made many references to reported or anticipated discoveries; but nothing of any importance was found. In the winter of 1892-1893 the matter has again attracted some attention, only small quartz crystals and no diamonds were found, the name Diamond Basin having given color to the reported findings. Diamond Basin lies on the Snake river in Owhyhee county, Idaho. The excitement, intense for a time, subsided before the winter was over.
A few years ago reports were started of the finding of diamonds in central Kentucky. Prof. Edward Orton, the State Geologist of Ohio, visited the district and observed certain resemblances to the diamondbearing region of South Africa. He found dykes of eruptive rock (peridotite) breaking through fissures in shale, and spreading to some extent over the adjacent country. Garnets and other associated minerals derived from the decomposition of the peridotite were found, suggesting the possibility of a diamond yield from the similarity of the conditions to those of Africa. And the diamonds found at Dlaschkowitz, Bohemia, the writer attributes to similar conditions of occurrence.(a)
Similar investigations and results were reported by Prof. A. B. Crandall.(6)
It had been previously suggested by Messrs. E. J. Dunn, E. Cohen, H. Huddleston, and Bupert Jones, that the South African diamonds were formed in a sort of volcanic mud (Mr. Huddleston), by a process rather hydrothermal than igneous, resulting from the action of steam in contact with magnesian mud, under pressure upon carbonaceous shales.
In the chemical laboratory of the U. S. Geological Survey, Prof. J. Edward Whitfield found 37.52 per cent, of carbon in the shale from near the Kimberly mine, while in the blackest shale adjoining the peridotite of Kentucky he found only 0.68 per cent, of carbon. The peridotite at the time of its intrusion must have beeu forced up through a number of coal beds and at a greater depth it penetrated the Devonian black shale, which is considerably richer in carbon than the shale now exposed at the surface.
A small diamond field has lately been found in Pierce County, Wisconsin. Here gold occurs in the gravel and sand along Plum Creek and its smaller tributaries; and some sluicing has been done by private parties. During 1887 and 1888 several small diamonds were found in the
o Trans. Am. Inst. Min. Engineers, 1892, p. 241.
b Note on the peridotite of Elliott county, Kentucky. Am. Jour. Sci., in Vol. 32, p. 121, Aug., 1886.