OCR Text |
Show WASHINGTON NOTES QUICKSILVER DEPOSITS OF OREGON AND NEVADA The Opalite quicksilver district the center of which is about 16 miles west of McDermitt, Nevada has been examined by R. G. Yates, geologist of the Geological Survey, Sur-vey, United States Department of the Interior. This work is part of the investigation of domestic deposits of strategic minerals being be-ing made by the Survey. McDermitt is 74 miles nrth of Winnemucca, Nevada, and the district, dis-trict, which is about 20 miles in diameter, lies partly in Malheur County, Oregon, and partly in Humbolt County, Nevada. The district includes the Opalite, Bretz, and Cordero mines and one undeveloped un-developed prospect. The rocks of the district are horizontal lava flows of Miocene age overlain by lake beds of late Miocene age. They are cut by steep-dipping faults, and part of the fault fissures were channels for ascending cinnabar-bearing solutions. The ore deposits ire mainly lens-shaped masses of silicified lake-bed material called "Opalite," but some ore occurs in unsilicified lake beds adjacent to the "opalite." All the ore bodies that have been found have been located within 100 feet of the surface. Siliceous ore has yielded an average of 6 pounds of quicksilver quick-silver to the ton; nonsiliceous ore has yielded about 19 pounds to the ton. Geologic conditions in the district dis-trict warrant the hope that new ore bodies would be discovered by more extensive prospecting. Three areas are particularly promising. One lies between the old pits and the 1940 pit of the Bretz mine another includes the silicified rocks a quarter of a mile southeast south-east of the old Bretz mine, and still another lies one half mile south of the Opalite mine. All the tuffs and sedimentary rocks adjacent to the silicified rocks at the Disaster Peak prospect seem to be possible host rocks for cinnabar. cin-nabar. m |