Hope Uranium Prospect, Bristol Mountains, San Bernardino County, California

Hope Uranium Prospect, Bristol Mountains, San Bernardino County, California Gregg Wilkerson 2017 Acknowledgement and Disclaimer The information in this paper is taken largely from published sources. I have reproduced this material and present it pretty much as I found it, not trying to harmonize discrepancies in prospect descriptions. I have changed verb tenses for readability and have used some paraphrase. Authors of the original information are indicated at the end of each paragraph. Paragraphs without a citation are my own material. LOCATION 6N 13E Sec. 18 SBM

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MRDS

The Hope uranium prospect is located in Section 18, Twp 6 N., Rge. 13 E., in the Bristol Mountains (Bonham and others, 1959, p. 5). The mine is southeast of Windy Point Ridge, 5.5 miles east-northeast of Amboy. See Figures 1 and 2. OWNERSHIP AND HISTORY None described. GEOLOGY The following is extracted from the Southern Pacific report (1959) for T.06N-R.13-14E, SBM by Bonham and others. The prospect is of interest chiefly because of the rare suite of fluorine-boron minerals associated with the uranium mineralization. Chesterman and Bowen (1958, p. 18, 19) have examined and reported on the prospect. They state that the uranium, fluorine and boron mineralization occurs at the contact between nordmarkite. ( quartz-rich syenite) and dolomite. They list the following minerals as occurring in the contact zone; fluoborite, forsterite, fluorite, chondrodite, diopside, tremolite, calcite, dolomite, warwickite?, szaibelyte?, brucite, serpentine, magnetite, uranophane, beta-uranotil and an unidentified mineral (Bonham and others, 1959, p. 6). Chesterman and Bowen (1958, p. 19) list the following sequence of metasomatism: (1) early phase, formation of the calcium-magnesium minerals; (2) middle phase, formation of the fluorine-boron minerals; and {J) late phase, formation of the uranium-bearing minerals and late fluorite (Bonham and others, 1959, p. 6). Max Schafer examined the prospect during the course of field work in Twp. 6 N., Rge. 13 E., and the following description and elevation is taken from notes by him. A shaft and inclined shaft penetrate a siliceous dolomite in the center of Section 18. The workings are located along a contact between dolomite and nordmarkite (syenite). Near the contact between the Syenite and dolomite, intensive silicification has taken place. Contact metasomatism has produced a suite of light-colored calcium-

magnesium silicates. Small shears have probably controlled the later deposition of the fluorine-boron minerals and the uranium minerals (Bonham and others, 1959, p. 6). According to L. R. Benson (oral communication) of Amboy, California, owner of the claims, several pods of high-grade uranium ore have been developed in the inclined shaft, but the present market outlook for uranium and lack of funds have discouraged any further development (Bonham and others, 1959, p. 6). The zone of metasomatic alteration and faulting was also found in a stream gully, approximately onethird mile south of the main shaft. At this locality the contact zone contains garnet and serpentine (Bonham and others, 1959, p. 6). Several samples were obtained from the dump of the main shaft. They consist of white to tan silicated dolomite, colored pale to dark purple by finely crystalline fluorite. Yellow uranium minerals occur as fracture coatings. One sample had five times background radioactivity (Bonham and others, 1959, p. 6). The important fact in this occurrence is the presence of a contact metasomatic zone in the carbonate rocks. Commonly the contacts between syenite and carbonate rocks are very sharp with no sign of metasomatic alteration or they are fault contacts. No other similar tactites were seen in the part of the Bristol Mountains included in Twp. 6 N., Rge. 13 E (Bonham and others, 1959, p. 6). Judging only from a brief examination of the surface, (the underground workings were not examined), it would appear that the best chance for any commercial exploitation of the deposit lies in the presence of certain rare-earth minerals. There appears to be little chance of any commercial quantities of uranium ore being developed in the mine (Bonham and others, 1959, p. 6). Kumpfer and Bassett (1962) mapped the area of the Hope Uranium Prospect as Pre-Tertiary lightcolored plutonic rocks, mostly quartz monzonite and granodiorite (pl). See Figure 3. Southern Pacific (1959) mapped the area as a tactite zone in urassic-Cretaceous Bristol Mountain Syenite (JKbsy). See Figure 4. REFERENCES Bonham, H. F., 1957 ,. Geology and mineral resources of Twp. 3 N., Rges. 9 and 10 E., SDBM, San Bernardino County, California: So. Pac. Co. files, (unpublished}. Bonham, H.F., 1959, Special report, lease examination, Sections 21, 20. 33. Township 6 N., Range 14 E., San Bernardino County, California: So. Pac. Co. files, S.F. (unpublished). Bonham, H.F., Jr., Max Shafer, and James Cooksley, 1959, Geology and Mineral Resources of Township 6 North, Ranges 13 and 14 East, San Bernardino Base and Meridian, San Bernardino County, California, Southern Pacific, unpublished report. 40 p. Chesterman, C. W., and Bowen, O. E., 1958, Fluoborite from San Bernardino County, California: (abstract): Geol. Soc. Amer. Bull. vol. 69, no. 12, p. 1678. Kumpfer, Donald H. and Allen M. Basset, 1962, Reconnaissance Map of Part of the Mojave Desert, California, in “A Geologic Reconnaissance of the Southeastern Mojave Desert”, California Division of

Prospects and Geology Special Report 83 and U.S. Geological Survey Mineral Investigations Field Studies Map MF-205 scale 1:125K. Minobras, 1978, Uranium Deposits of Arizona-California, p. 91. MRDS, 2011, Mineral Resources Data System, U.S. Geological Survey, https://mrdata.usgs.gov/mrds/ Southern Pacific Company, 1964, Minerals for Industry, Volume III – Southern California, California Division of Prospects and Geology, Special Report 95, 242 pages plus maps. The data in this report is based on geologic maps Southern Pacific produced pre-1964 covering two townships each. These maps create a mosaic of township geologic maps throughout much of the Mojave Desert. These have been scanned and rectified and are on file with the Bureau of Land Management, Riverside, California. Southern Pacific, 1959, Geology and Mineral Resources of T.06N-R.13-14E, SBM with report and map. MAPS

Figure 1. Regional topographic map of the Hope Uranium Prospect and surrounding area.

Figure 2. Topographic map of the Hope Uranium Prospect and surrounding area.

Figure 3. Geologic map of the Hope Uranium Prospect and surrounding area. Adapted from Kumpfer and Bassett, 1962.

Figure 4. Geologic map of the Hope Uranium Prospect and surrounding area. Adapted from Southern Pacific, 1959.