The Silver-Lead Deposits of Eureka, Nevada

Abstract

THE remarkable mineral district which is dealt with in this memoir is situated in the eastern part of the State of Nevada, about the centre of the dreary region known as the Great Basin, between the Great Salt Lake of Utah and the Sierra Nevada range of California. The business centre of the town, or “mining camp,” of Eureka is about 90 miles south of the Palisades Station, on the Central Pacific Railway, with which it is united by a narrow-gauge branch railway. The principal mines situated about Ruby Hill, about 11/2 miles west of the town, extend for about a mile along the contact of a limestone, supposed to be of Cambrian age, with an underlying quartzite. The quartzite forms the axis of a steep anticlinal arch, which has been modified, on one side by a great fracture known as the Ruby Hill fault, and between this and some secondary fractures, an enormous mass of crushed limestone is included, containing the mineral deposits, or ore bodies proper, which are essentially cave deposits, the hollows between the limestone fragments, which are of all sorts of shapes and sizes, being filled with products of the —oxidation of galena, pyrites and mispickel, such as sulphate, carbonate, and arsenate of lead, and brown iron ore, in addition to the unaltered minerals in smaller quantities. The chief mineralogical find of these mines has, however, been of Wulfenite or molybdate of lead, which has been produced in considerable quantity, both in detached crystals of great beauty and interspersed through the mass of the other minerals. As a whole, the ores contain about 33 per cent, of lead, 30 ozs. of silver, and about 13/4 ozs. of gold per ton. These ore bodies are of every possible form and size, from small strings up to masses measuring upwards of 100 feet in all directions; but in spite of this great irregularity of form, they are generally connected with systems of fissures or channels, and it is by following these fissures that most of the great discoveries have been made.

The Silver-Lead Deposits of Eureka, Nevada.

By J. S. Curtis. 4to. 200 pp. (Washington, D.C., Government Printing Office, 1884.)