Bristol Dry Lake Calcium-Gypsum-Anhydrite-Halite Deposit, 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. 27 SBM 34.57502000020-115.72054000000 MRDS This mine is 1.8 miles northeast of the town of Amboy. OWNERSHIP AND HISTORY This deposit was formerly known as the National Chloride Co. of America; Hollar Chemical Co.; and Saline Products Co. (MRDS). Emilie Cloudmax summarized the history of this mine in 1915: San Bernardino County contains gypsum deposits in many places on the desert, the most notable, and at present the only one worked, being that of the Consolidated Pacific Cement Plaster Company in the Amboy sink (Cloudmax and others, 1915, p. 868). Figure 1. Pacific Gypsum, circa 2015. From Cloudmax and others, 1915, p. 869 1
In 1915 the Bristol Lake-Amboy deposit was operated by Consolidated Pacific Cement Plaster Company, office, 612 San Fernando Bldg., Los Angeles; J. D. Bowersock, president; D. A. Mulvane, secretary. This company, formerly known as the Pacific Cement Plaster Co., had been working the Amboy dry lake deposit 2 miles southeast of Amboy for the past ten years (1905-1915). This lake bed is very extensive, covering several thousand acres, and is of a type common to the Mojave Desert. The gypsum occurs loosely cemented with sand in coarse crystals up to ¼ inch across, deposited in a bed varying from 4' to 6' in Photo No. 44. Plant of the Pacific Consolidated Cement Plaster Company at Amboy, Cal. thickness covered with a thin sandy soil. The surface is stripped by horse scrapers to a depth of about 1 ft and the gypsum was then plowed down and scraped up to a platform (see Cloudmax and others, 1915, photo No. 43) through which it was dumped into tram cars below (Cloudmax and others, 1915, p. 869).. Figure 2. Pacific Gypsum, circa 1915. From Cloudmax and others, 1915, p. 869. The cars were drawn by a small steam locomotive, hauling 20 tons to a trip, to the company's mill at Amboy, where it was crushed, washed, and calcined. Both hard (wall) plaster and cement plaster were manufactured, the latter being shipped to the cement plants of southern California at Riverside, Colton, Oro Grande and Victorville. Power to operate the mill was supplied by a 400 h.p. Corliss, crosscompound, condensing, steam engine. Crude oil was used for fuel. Water was brought from the Santa Fe Railway Company. In 1915 the company was working only one shift, producing approximately 100 tons daily. Thirty men were employed. Mexican labor was used at the quarry. F. E. Towne Jr., was manager at the property (Cloudmax and others, 1915, p. 870). 2
Figure 3. Pacific Gypsum, circa 1915. From Cloudmax and others, 1915, p. 870 GEOLOGY The Amboy deposit was described by Hess (1910). His description is reproduced, below: Amboy, a station on the Santa Fe Railway in the Mohave Desert, San Bernardino County, about 225 miles from Los Angeles, is on the shore of a periodic lake, along the north side of which the railway extends in an east-west direction for 6 or 8 miles. The gypsum deposits are in the lake bed, probably stretching nearly around it. This lake bed is of a type common in the Mohave Desert and is a number of mile's in extent. The surface soil is salty, so that almost no vegetation grows on it. The lake receives drainage from mountains on both the north and the south, but it is rarely that sufficient rainfalls in the mountains, to furnish the streams enough, water to cover the surface of the dry bed. At the time of visit (January 22, 26 1907) a strong brine was reached in the lake bed at a depth of about 8 feet (Hess, 1910, p. 25-26). A small volcano rises 3 miles west of the lake, and from this streams of basaltic lava have run over the lake bed. In the bays between these flows gypsum is found throughout the area, and the winds have blown it up into small drifts across the tongues of lava. Over a portion of the area a light volcanic ash forms the surface soil, a foot or more thick, and below this soil gypsum is found to a depth of 6 to 8 feet, at which point the water level is reached. It is not known how far the gypsum may extend below water level. Many prospect holes have been dug along the north and east shores of the lake and gypsum was found only within about half a mile or a mile of the shore line (Hess, 1910, p. 25-26). The gypsum varies considerably in character, both longitudinally and vertically. In many places the gypsum nearest the surface is rather dirty, while below that is a stratum, 14 inches to 2 feet thick, of clean, white granular gypsum. In places the gypsum is cemented into a clean, spongy mass, which has little solidity but can be broken out in chunks a foot or more in diameter. At other places the gypsum crystals reach an inch or more in breadth but are thin in proportion. There is also considerable variation 3
in the amount of dirt present. It is reported that gypsum occurs on the south side of the lake bed, and the probability is that the deposits will be found along a considerable proportion of its circumference. The character of the rocks in the hills is unknown, but there are crystalline rocks on both sides and more than likely young sedimentary rocks also (Hess, 1910, p. 25-26). In a prospect hole 2 miles east of Amboy no water appeared at a depth of 9 ½ feet and the gypsum does not have the salty taste which is common to the gypsum on the west side of the lake. Gypsum is found all the way to the bottom. The uppermost 2 feet is rather dirty. Below this is 2 feet of much cleaner material, while the lower 4 feet is iron stained and dirty. The gypsum is coarse grained, the crystals reaching one-fourth inch across, and in general is loose but includes some hard layers and seams (Hess, 1910, p. 25-26). The Hess (1910) report describes that a sample of the lower 4 ½ feet of the gypsum exposed in the hole was taken by cutting a narrow strip from the top to the bottom of the stratum. A partial analysis of the sample by George Steiger is as follows: Partial analysis of gypsum from a point 2 miles east of Amboy, Cal (Percent) Lime (CaO) 28.1 Sulphur trioxide (SO8) 34.9 Water driven off at 60 C. 00.8 Water driven off at 300 C 05.2 Chlorine (Cl) 01.4 Iron oxide (Fe2 03) 01.0 Kumpfer and Basset (1962) mapped the area of the Bristol Dry Lake Pit as Qoa (Older Alluvium). The Southern Pacific Company (1964) mapped the area as Qal (Quaternary alluvium) and Qoal (Older Quaternary Lake Beds). REFERENCES Cloudmax, Emile Huguenin, F. J. H. Merrill, and Burling Tucker, 1919: Mines of San Bernardino and Tulare Counties, Report of the State Mineralogist, Volume 15-16, Part IV. P. 773-945 -Pacific Gypsum p. 868-870. California Division of Mines and Geology Bulletin 38, p. 287; Hess, Frank. L., 1910, A reconnaissance of gypsum Deposits of California, USGS Bulletin 413, pp. 25-27. 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 Mines and Geology Special Report 83 and U.S. Geological Survey Mineral Investigations Field Studies Map MF-205 scale 1:125K. MRDS, 2014, Mineral Resource Data System, US. Geological Survey, https://mrdata.usgs.gov/mrds/ 4
Southern Pacific Company, 1964, Minerals for Industry, Volume III Southern California, California Division of Mines and Geology, Special Report 95, 242 pages plus maps. Southern Pacific Company, 1964, Geologic map of T.6N-R.11-12E, BM. MAPS 5
Figure 4. Regional topographic map of the Bristol Dry Lake Pit. 6
Figure 5. Topographic map of the Bristol Dry Lake Pit with PLSS data. 7
Figure 6. Regional geologic map of the Bristol Dry Lake Pit and surrounding area. Adapted from Kumpfer and Basset, 1962. 8
Figure 7. Geology of the Bristol Dry Lake Pit and surrounding area. From Southern Pacific Co., 1964. 9
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