Amboy Iron Mines, Bristol Mountains, San Bernardino County, California. Gregg Wilkerson 2017

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1 Amboy Iron Mines, 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 mine 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 12E Sec. 07 SBM (Occurrence, Lillian, MRDS) 6N 12E Sec. 17 SBM (Prospect, Magnetite, MRDS) 6N 12E Sec. 08 SBM (Prospect, Lower, Topographic Map) Wright and others (1953) describe the Amboy Iron Deposits as being in Sections 7 and 18, T. 6 N., R. 12 E, S.B.M., on the southwestern slope of the Bristol Mountains (Wright and others, 1953, p. 89). Southern Pacific (1956) gave a slightly different location: The Amboy Iron deposits are in the N1/2 Section 17, T.6N., R.12E., SBBM, San Bernardino County (Southern Pacific, 1956, p. 131). OWNERSHIP AND HISTORY Lauren Wright and others give this history of the deposit: Conn Pulos of Amboy, California owned nine unpatented lode claims and one 80-acre placer claim located for limestone in Early in 1951 an open cut was made on the lens and a few thousand tons of low grade ore was stockpiled; no ore was shipped (Wright and others, 1953, p. 89). In 1958, the Southern Pacific Co. report for T.6N, R,12-13E reported: Several thousand tons or ore are exposed in pit 150' by 100' by 20' deep; estimated 1000 long tons of magnetite-hematite clasts in material removed from pit; representative sample of clasts assayed 60% Fe, 0.12% Ti, 0.316% S, and 0.017% P (Southern Pacific, 1964, p. 131). GEOLOGY Wright and others described the geology of the Amboy iron deposits this way: The Amboy claims have been located to cover three separate deposits of iron ore on only one of which has any appreciable work been done. A description of two of these, the Lillian and Magnetite has been given in a private report (Penhole, 1951). The Lillian deposit consists of several small lenses of hematite in limestone near a contact with granitic rock and it has been explored by a 10-foot shaft and shallow

2 cuts. The Magnetite deposit, located about 3000 feet farther east, consists of magnetite-hematite vein striking N. 80 W. along the contact between limestone and granitic rock ; the latter contains considerable magnetite. The vein dips steeply to the south at a sharp angle to the limestone bedding which dips 60 S. The width of the vein ranges from 5 to 30 feet and the outcrop length is approximately 2000 feet. Exploration work consists of two small cuts (Wright and others, 1953, p ). The Lower deposit, 1200 to 1500 feet southeast of the Magnetite deposit and several hundred feet lower in altitude, consists of a roughly elliptical lens of impure brecciated hematite in limestone; the lens is about 75 by 250 feet in size (Wright and others, 1953, p. 90). Southern Pacific had an unenthusiastic interpretation of the economic viability of the Amboy Iron Deposits: The deposits are magnetite and hematite replacement lenses that strike generally N45 W in marble near contact with syenite. There is a small reserve of magnetite-hematite ore (Southern Pacific, 1964, p. 131). Lower grade iron ore (magnetite and hematite) occurs along the contact tactite zone of the syenite and meta-igneous complex. Has potential use as source of heavy aggregate (Laird, 1959). The Magnetite mine is near a west-northwest to east-southeast striking fault that is down to the southwest. The MRSD locations for this deposit when compared to the mapped geology of the area suggest that the limestone-granitic contacts are in Section 7, 8 and 17 of T.6S, R.12E. Dibblee (2008d) mapped this area as pre-mesozoic limestone (ml) and Mesozoic quartz diorite (qd). Kumpfer and Bassett (1962) mapped the MRSD location for the eastern occurrence as in alluvium near undifferentiated plutonic and metamorphic rocks. Given the scale of that map, and errors inherent if scanning and rectification of maps made under different projections, and using different mapping bases for the original field work, I am sure the mine locations are in the ml and qd units, not the Qal unit. Laird (1959) mapped the area of the Magnetite deposit as fault with PreCambrian metamorphic complex (P mi) to the northeast and Metacarbonate rock with some aplite and other intrusives (mbd) to the southwest. A regional geologic mosaic of the Bristol and Old Dad Mountains is at: A regional stratigraphic compilation for this mosaic is at: tains_san_bernardino_county_california_text REFERENCES Kumpfer, Donald H. and Allen M. Bassett, 1962, Reconnaissance Map of Part of the Mojave Desert, California, in A Geologic Reconnaissance of the Southeastern Mojave Desert, California Division of

3 Mines and Geology Special Report 83 and U.S. Geological Survey Mineral Investigations Field Studies Map MF-205 scale 1:125K. Laird, R.T, 1959, Geology and Mineral Resources of Township 6 North, Ranges 11 and 12 East, San Bernardino Base and Meridian, California, 33 pages with geologic map of T06N-R11-12E, S.B.M, Southern Pacific Company, 1959, unpublished report. Lauren A. Wright, Lauren A., Richard M. Stewart, Thomas E. Gay, Jr., and George C. Hazenbush, 1953, Mines and Mineral Deposits of San Bernardino County, California, California Journal of Mines and Geology, v. 49, p of 192. MRDS, 2011, Mineral Resources Data System, U.S. Geological Survey, Penhoel, L., 1951, Lillian and Magnetite Mine, Bristol Mountains, California, Private report, Cited by Wright and others, 195, p. 87. Southern Pacific Company, 1964, Minerals for Industry, Volume III Southern California, California Division of Mines and Geology, Special Report 95, p. 131 of 242. MAPS

4 Figure 1. Regional topographic map of the Bristol Mountains showing location of the Amboy Iron deposits.

5 Figure 2. Topographic map of the Amboy Iron Deposits.

6 Figure 3. Geologic map of the Amboy Iron deposits and surrounding areas. Adapted from Dibblee, 2008d (west part) and Kumpfer and Bassett, 1962 (east part).. Commented [DG1]:

7 Figure 4. Geologic map of the Amboy Iron Deposits. Adapted from Southern Pacific, 1964.

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