SELECTED REFERENCES CONTAINING PLACER COST DATA
Averill, Charles V., Dragline dredging in Siskiyou County: Thirty-seventh Report of (Calif.) State Mineralogist, pp. 328-33l. April, 1949. Costs of principal items of equipment noted. Also cost of a resoiling project.
Bureau of Mines Staff, Minerals Yearhook, annual volumes. Current economic trends and effects on mining industry. Production potential of known gold deposits in the United States: U.S. Bureau of Mines Information Circular 8331, pp. 11-14, 1967. Notes current cost estimates for dredging, drift-mining and hydraulicking. Also capital cost for bucket-line dredges.
Chellson, Harry, C., What will it cost to work a gold placer of medium size? Engineering and Mining Journal, Vol. 135, No. 10, pp. 441-445. October, 1934. Costs for various size operations using a mohile dryland washing plant.
Daily, A.F., Chapter 13.5 (Placer Mining) in AIME Surface Mining volume: Puhlished by Amer. Inst. of Mining, Metallurgical and Petroleum Engineers, Inc., New York. 1968.
Eassie, W. H., What does hydraulicking cost? Engineering and Mining Journal, Vol. 145, No.6, pp. 92-94. June 1944. 1939-1941 costs for a medium-size hydraulic mine in British Columhia, Canada.
Gardner, E. D., and Allsman, Paul T., Power-shovel and dragline placer mining: U.S. Bureau of Mines Information Circular 7013,68 pp., 1938. Detailed cost data for floating and stationary plants.
Gardner, E. D., and Johnson, C. H., Placer Mining in the Western United States.
1. General Information, hand-shoveling, and ground sluicing: U.S. Bureau of Mines Information Circular 6786, 73 pp. 1934.
2. Placer mining in the Western United States. II. Hydraulicking, treatment of placer concentrates, and marketing of gold: U.S. Bureau of Mines Information Circular 6787, 88 pp. 1934. Contains operating and cost data on small-scale hydraulicking.
3. Placer mining in the Western United States. III. Dredging and other forms of mechanical handling of gravel, and drift mining. U.S. Bureau of Mines Information Circular 6788, 81 pp., 1935.
Lord, Harry S., Modern dragline dredging: Mining World, Vol. 3, No. 10, pp. 14-16. Oct., 1941. Cost of principal items of equipment for 1/2 cu. yd. to 12
cu. yd. dragline dredges.
Magee, James F., A successful dragline dredge: A.I.M.E. Trans., Vol. 126 (1937), pp. 180-200. Contains detailed operating data for a typical dragline dredge.
Patman, Charles G., Methods and costs of dredging auriferous gravels at Lancha Plana, Amador County, California: U.S. Bureau of Mines Information Circular 6659, 17 pp. 1932. Describes construction, operation, and operating costs of a 6-cu. ft. bucket-line dredge.
Romanowitz, Charles M., Floating dredges used for mining purposes: Mineral Information Service, Vol. 20, No.7, pp. 82-87. July, 1967. (Published by California Division of Mines and Geology). Discusses onshore and offshore dredging including tin and other minerals. Compares hydraulic (suction) dredges and bucket-line dredges. Notes dredging costs in South America and Yukon Territory. Reviews history of dredging and latest developments.
Staley, W. W., and Storch, R. H., Choosing a mining method for gold-bearing gravels, Part I: Engineering and Mining Journal, Vol. 138, No.7, pp. 342-346; also p. 359, July, 1937. Part II: Vol. 138, No.9, pp. 43, 44. Sept., 1937. Develops hypothetical mining programs and comparative costs for working a placer (in Alaska) by hydraulicking, power drag-scraper, and dredging. A good example of a placer cost study.
Thomas, Bruce I., Cook, Donald J., Wolff, Ernest, and Kerns, William H., Placer mining in Alaska: U.S. Bureau of Mines Inforamtion Circular 7926, 34 pp. 1959. Describes mining methods and gives unit operating costs at operations where hydraulic and mechanical equipment is used with nonfloating washing plants, including sluiceplate mining operations.
Thurman, Chas. H., Costs in dragline gold dredging: A.I.M.E. Technical Publication No. 1900 (1945), 6 pp. Compares bucket-line and dragline dredge costs. Gives examples of equipment and operating costs.
5. UNPROVEN PROCESSES
Many special placer machines or secret recovery processes have been "invented" or proposed. Some claim the ability to extract microscopic or colloidal gold from materials that show little or no value when tested by fire assay or by the normal methods of testing placer material. Others are intended to recover the varying amounts of fine gold admittedly lost in large-scale placer operations. These devices or schemes seem to have an unfailing attraction for miners as well as for the general public.
But despite the many "improved" placer machines and the new gold-saving methods that have been offered, the simple Hungarian-type riffle has held its place in the placer industry while most of its rivals have been discarded. A notable exception is the placer-type jig which has supplemented the riffled tables (sluices) in some dredging operations and has replaced them in others.
It can be said generally that the success of a placer operation will hinge on the throughput, a high throughput being the key to low costs. In other words, the greater the throughput the lower the unit cost. Experience has shown that to achieve the optimum working rate some recovery must be sacrificed, or put simply, it is cheaper to lose a certain amount of gold than to save it.
To date no one has demonstrated a placer recovery system that can economically replace today's methods and equipment. Operating economies made possible by the large capacity and the simplicity of conventional riffles and placer jigs more than offset the dollar value of the gold they may lose. On this basis, they yield the greatest operating profit.
Even where a new or improved recovery method may be shown to possess some potential, if it is not yet at the stage where it can be presented as a proven method or technique, the mineral examiner has little choice but to rely on standard anaytical and recovery methods when making his evaluation.
REFERENCES CITED (PART VI)
Clifton, H. Edward, Hubert, Arthur, and Phillips, R. Lawrence, Marine Sediment Sample Preparation for Analysis For Low Concentrations of Fine Detrital Gold: U.S. Geol. Survey Circular 545, 1967. 11 pp.
