Dernan Property, Potosi Mining District, Osgood Mountains, Humboldt County, Nevada, USAi

Regional Level Types
Dernan Property	Property
Potosi Mining District	Mining District
Osgood Mountains	Mountain Range
Humboldt County	County
Nevada	State
USA	Country

Structure: Getchell Fault Cuts S. End Of Ore Body Fault Along Front Of Range

Commodity: 1943-1944, 80,000 tons ore avg. 0.63% wo3=50,400 units wo3; 1945, 8500 tons ore avg. 0.70% wo3=5950 units wo3; 1952-1955, 264,600 tons ore avg. 0.57% wo3 = 150,822 units wo3. Production from 1945 to 1948 is unknown, but it was substantial, As the riley mine was nevada's 2nd largest producer of tungsten concentrates in 1947.

Deposit: Discovery year: wwi era the property is along the east contact of the northern lobe of the osgood stock with limestone and interbedded argillite striking n, dip 30-60 E (both bedding and contact). A b-and of tactite 3-20 ft thick is present along much of the contact and in places extends up to 40 ft out into the limestone. The tactite extends As much As 500 ft down dip to the point where the granodiorite contact dropped belo W the e-dipping limes-tones. At the south end of the property the tactite lenses are- cut off by the getchell fault. The four major orebodies occur- along a strike length of 1700 ft along the contact, localized- by troughs of e-dipping folds cut by the contact. The ore zones extended onto the riley extension mine property to the north mine operated As open pit from 1942 to 1945. Some production by u.s. Vanadium corp from 1945 to 1948. Mine was reopened in 1952, and operated both underground and open pit throgh 1957. In 1945, a mill was erected by northern nevada mining corp, and a small amount of ore was treated before it was bought by u.s. Vanadium corp. (later union carbide nuclear corp.) the area was prospected during wwi, but little, if any, tungsten was then produced. Riley and riley extension mines comprise the largest single tactite deposit in the district early exploration was for silver ore. The presence of scheelite was known since about 1917, but it was not mined until world war ii. Scheelite ore was mined from a series of eight pits along the tactites. ; info.src : 1 pub lit; 2 unpub rept; 3 field observ

Deposit type: W skarn

Development: The property consists of 80 acres of patented ground that is part of the tom dernan estate. It was leased to Mr. J. E. Riley of reno in the fall of 1942 and was developed and -operated by him in 1943-1944, yielding about 80000 tons ore averaging 0.53 % wo3, that was sold to metals reserve co for the nearby getchell stockpile. A mill was built on the property, in the winter of 1944-45 and an additional 8000 tons ore was mined and milled before the property was sold to the u. S. Vanadium corp. (later union carbide corp.) in october, 1945. All of the ore produced to the end of 1945 came from 8 open pits along the outcrop. In 1945 the USBM explored the deposit by 15 d-iamond drill holes having an aggregate length of 2630 ft, and added greatly to the known reserves. From late 1945 to 1948 and from 1952 to 1957 the property was operated by u. S. Vanadium corp. And then union carbide corp, with a large production of ore from open pits and underground workings.

Geology: The granodiorite contact trends generally north: the "East vein" extends along the granodiorite contact for about 1600 feet at surface, mined on both riley and riley extension properties. The main ore body was a tabular tactite body mined for approx. 800 ft. Down dip, averaging 10 ft. Thick. The shear zone exposed in the cuts at the riley mine contain several tens of feet of marginal gold ore (getchell-type). Tungsten ore bodies are localized in "troughs" formed by jogs in the attitude of the igneous/sedimentary contact. There are 4 such distinct ore bodies.

Rock formation(s): Preble Formation;Preble Formation;Preble Formation;Osgood Mountains Stock


Ore(s): Tactite Zone Near Granodiorite Contact

Other Databases

Link to USGS MRDS:	10037016

References