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Home , Arrastra, Beneficiation, Gangue, Mineral processing, Patio process, Stamp mill

A HISTORY OF CONCENTRATION:

A HISTORY OF TAILINGS1

by

Timothy c. Richmond2

Abstract: The extraction of mineral values from the earth for beneficial use has been a human activity- since long before recorded history. Methodologies were little changed until the late 19th century. The nearly simultaneous developments of a method to produce of a uniform carbon content and the means to generate electrical power gave man the ability to process huge volumes of of ever decreasing purity. The or waste products of were traditionally discharged into adjacent streams, lakes, the sea or in piles on dry land. Their confinement apparently began in the early 20th century as a means for possible future mineral recovery, for the of water in arid regions and/or in response to growing concerns for water pollution control.

Additional Key Words: Mineral

" ... for since Nature usually creates metals in an impure state, mixed with earth, stones, and solidified juices, it is necessary to separate most of these impurities from the ores as far as can be, and therefore I will now describe the methods by which the ores are sorted, broken with hammers, burnt, crushed with stamps, ground into powder, sifted, washed ..•. " Agricola, 1550 Introduction identifying wastes. It is frequently used mistakenly The term "tailings" is to identify all mineral wastes often misapplied when including the piles of waste rock located at the mouth of 1Presented at the 1.991. National mine shafts and adi ts, over- American. Society for Surface burden materials removed in Mining and Reclamation Meeting , wastes from in Durango, co, May 1.4-17, 1.991 concentrating activities and sometimes the wastes from 2Timothy c. Richmond, Project operations. For the Officer, Abandoned Mine Land purpose of this discussion, the Program, Wyoming Department of following definitions shall Environmental Quality Cheyenne, apply: WY 82002

Page 369 Tailings: Tailings are the improvement after mining but finely ground or host before smelting and which rock materials from which the includes the milling process. desired mineral values have been extracted during the Mining, concentrating and concentration process. smelting of ores for their Tailings may contain the metals have been a part of residues of reagent materials human activity since before that were added to enhance recorded history. The mineral mineral separation (Young 197 6, processing methods remained PEDCO 1984) . Tailings will basically unchanged from usually have the same ancient times until the latter mineralization as the host part of the 19th century. rock. "Chat" is a term used in certain regions of the United The disposal of mineral states for tailings. Waste wastes did not present much of materials derived from the a problem to human health and processing of coal, including welfare until the first part of the terms "refuse, 11 "slack," the twentieth century. and "gob" are often incorrectly However, as the modern mining referred to as tailings {Thrush industry continues to satisfy 19 68) • the increasing demands for metal and other mineral : Slag is the impurities products, mine wastes and and reject material formed tailings will also expand in during the smelting or ever increasing proportions. of ores or mineral concentrates About 362,872,000 metric tons by pyrometallurgical methods of tailings were generated {Thrush 1968). Slag is the annually in the United States generally accepted term in the alone in the early 1970's (Dean United states for wastes et al 1974). A decade later, produced from the smelting it had increased to 598,771,900 process, but may occasionally metric tons, exclusive of be used to define any or all of uranium mining (PEDCO 1984). the mineral industry waste products. Early Methodologies Beneficiation: Beneficiation is There is little doubt that the upgrading of by sizing, the first discoveries of , removal of impurities or and were found in otherwise improving the quality their free. or native state as of the ore {Thrush 1968). nuggets lying on the surface of Beneficiation can apply to any the ground or in pools of water ore grade improvement from in streams and rivers. Such sorting in the mine through finds were opportunistic, but concentration prior to early man quickly learned where smelting. to look for these metals. It was soon discovered that by concentration: Concentration is digging and washing sands and the separation and accumulation gravels in certain streams, or of economic mineral values from from their banks, gold nuggets gangue {Thrush 1968). would be found. Where water Concentration is generally was not available, the earth limited to ore quality could be winnowed or tossed

Page 370 into the air from an animal hammered or pried free to be hide or perhaps a woven fabric, carried to the surface. and the lighter materials would Particles of the host rock were be carried away by the wind in often attached to the metals much the same manner that chaff and had to be broken free and was separated from kernels of discarded. grain. This was the beginning of what is commonly termed Somewhere along the way, , forms of which ancient man learned that some are in common use today. It is of the mineral forms of metals a method that many consider could be refined to an almost among the most ancient methods pure state by the use of fire of separating metal from waste and heat. The discovery of (Young 1976). smelting by fire made additional ores useful, mainly Placering, with the most the oxide and carbonate ores of rudimentary pans, or the more copper. Smelting also provided sophisticated sluices, strakes, the ability to separate silver rockers and jigs, then as now, from lead, to refine gold by is the mechanical separation by removing the often naturally gravity of native or free metal alloyed silver and to mix and heavy metallic salts from with copper to make bronze. naturally crushed rock (Young 1976). These methods are most The desirability of removing often associated with gold the largest possible amount of recovery. The waste products gangue or earthy matter from of early pl.acering, tailings if the valuable metal before you will, were carried away to smelting had been recognized be deposited elsewhere with for thousands of years and was little or no apparent regularly practiced by ancient consequence.• peoples (Aitchison 1960). The earliest apparent indications The next step in the of mineral concentration are recovery of metals was the found as inscriptions on discovery that these metals, Egyptian monuments dating from along with tin and lead, could the IV Dynasty (about 4000 BC) . be found in their native state Other monuments dating from the in outcrops of rock, but first XII Dynasty (2400 BC) had to be broken loose. This specifically suggest the was the beginning of mining in working of gold ore (Hoover and the sense that it is commonly Hoover in Agricola 1912). perceived; the excavation of Written accounts of ancient metal-bearing rock, initially mineral concentration as surface expressions and then techniques are limited, most tunneling underground. The descriptions tracing back to tools of excavation were stone, the lost works of horn, bone, and in time, bronze Agatharchides, a Greek and . A fire, the primary geographer of the second loosening agent, would be built century, BC, who described against the metal-bearing face Egyptian mining and and the rock heated. Then concentration methods (Hoover water would be dashed against and Hoover in Agricola 1912). the hot rock causing it to The process involved breaking fracture. The pieces were then mine-run rock into smaller

Page 371 pieces using stone mortars and lashed to a forked stick that stone or iron pestles. The in turn was supported by small pieces, "the size of a another forked stick that acted vetch, " were then taken to a as a fulcrum. A flat rock with where they were further a slight depression served as a ground "as fine as meal. 11 This mortar. The ore was placed on finely ground powder was spread the mortar and crushed by over . a broad board or rough repeatedly raising and dropping stone slab, somewhat inclined the stone (Young 1976). or sloping, where it was washed by pouring water over the The was a common powdered rock. The material tool of the ancients. It was would be worked by hand over widely used in the Americas by the board or slab, the water the Spanish Conquistadors washing away the earthy during the sixteenth century, material and the gold, being and it found continued heavier, was retained (Hoover widespread use in the western and Hoover in Agricola 1912, Americas into the twentieth Poss 1975). century. The arrastra also employed stones lashed to a The famous ancient Greek pole. However, the pole was silver mines at Mount Laurion attached to a center pivot in a were extensively worked before tub made of very hard rock 500 BC, but it is unclear when spaced closely together to form the ores were first a tight, smooth floor. Men or concentrated before being animals would push on one end smelted. At some time before of the pole and the stones the Third Century, BC, an lashed to the other would extensive system of milling and finely crush or grind the ore concentration had been placed in the tub by an developed. One estimate abrasive action. The finely suggests that the Mount Laurion ground ore was recovered· for area produced more than further processing of the metal 6,350,000 metric tons of reject values. The arrastra was (tailings) over the several simple to build and could be centuries of its activity operated as either a wet or dry (Hoover and Hoover in Agricola grinder or as a separator. 1912) • could be added for its gold (and subsequently silver) The crushing appliances amalgamation properties (Young described by the ancient 1976). authors and confirmed by Greek and Roman artifactual remains The next apparent crushing scattered over Europe were hand development was the Chilean mortars and millstones of the Wheel, also known as an edge same order as those used to runner. This device was grind flour (Hoover and Hoover constructed and operated in a in Agricola 1912). Such similar fashion to the appliances were relatively arrastra, except that the stone simple affairs, and with a few drags were replaced by stone refinements, were employed into wheels that performed the the twentieth century. These crushing and grinding. As with included the most primitive of the arrastra, the Chilean Wheel mechanical implements, a stone would have to be dismantled

Page 372 frequently so that the fine early metallurgical processes grindings that had fallen other than those of the Greeks between the stones of the tub and Romans already referenced. could be recovered. Because it It was not until Georgius was more awkward to dismantle Agricola compiled the classic and reassemble than the about 1550 AD arrastra, there is conjecture that the first detailed that this implement, as well as description of mining, other wheeled variations, may concentrating and smelting have seen more use as a primary practices was produced. This rather than as a tool work was translated into for fine grinding (Young 1976). English by Herbert Clark Hoover Young also points out that the and Lou Henry Hoover in 1912. Chilean Wheel was used in biblical times for olive seed Agricola described in detail crushing and therefore the name the many methods and variations has no connection to its of ore washing, including the origin. common forms of placer mining as well as the washing of The products of these early crushed and finely ground ores. grinding procedures, including He described a form of jigging those from the hand operated as an ore washing technique mortar and pestle, were native that had been recently adopted metals, oxide, carbonate or by miners at the time. The jig some sulfide ores of metals, consisted of a sieve that was mixtures of the ores and gangue filled with ore and sifted in a or barren gangue . The vertical motion in a tub nearly grindings would be collected full of water. This action, and washed, utilizing the coupled with the movement of principle of gravity to the water in the tub, caused separate--· the heavier the heavier metal-bearing metalliferous material from the particles to sink while the gangue. The barren gangue lighter gangue floated to the would be discarded as tailings. top of the tub and was skimmed off for discarding. Mercury amalgamation of gold Another device described by was known as early as Roman Agricola was a machine 11 ••• that times (Hoover and Hoover in one in the same time can crush, Agricola 1912, Young 1976) and grind, cleanse and wash the became increasingly more common gold ore and mix the gold with over time as more mercury quicksilver .•.. " This device deposits were discovered. evidently included a stamp Mercury was often added to the mill, along with a wheel-type ore during these early grinding millstone arrangement and a processe·s and the amalgamated three-tub washer equipped with ore was subsequently washed to mechanical paddles that separate the gangue from the agitated and mixed the mercury . In these instances, with the pulp. This system was some mercury would be lost with water powered and water was the gangue as tailings. used to carry the ores through the amalgamation There is little in the and washing stages as well as written record to document to carry away the tailings.

Page 373 A new development of and restricted man's significance, the , ability to recognize, let alone was described by Agricola. It utilize, the multitude of metal was invented sometime in the ores known today. Of necessity late fifteenth or early then, minable ores were limited sixteenth century. It was a to the native or free metals water, animal or man powered and a very few of their oxide, device that employed a shaft _carbonate and sulfide forms. with cams which lifted heavy In all cases, the pure metal wooden rods that had iron shoes content of the ores was very attached to their base. At the high relative to today's common top of the lifting stroke, the cut-off grades. cam released the rod and the force of its fall crushed the 19th Century Developments ore fed beneath it. The stamp mill was more a result of an The 19th century brought emerging mechanical technology several major developments that rather than an increase in the would have everlasting- impacts knowledge of metals and on not only the metallurgical metallurgy. Significantly, the science and industry, but on methods of separating metal- all of human-kind as well. bearing components from barren Explosives, in the form of gangue in his time were the gunpowder, were first used in same as of old: water Germany for loosening rock in separation, and in the case of mines about 1627 AD (Poss gold, water separation of 1975), but their widespread use mercury amalgamated gold for this purpose would wait particles. until the development of dynamite in the latter part of Metallurgists in Agricola's the 1800s (Young 1976). time had a working knowledge of Electricity, first described by only nine metals, not including Volta and produced in wet cell such alloys as bronze, brass, batteries by Humphrey Davey in pewter and electrum. These 1807, would wait until the were the seven metals of invention of the dynamo in the antiquity: gold, silver, latter part of the 19th century copper, lead, iron, tin and before it could be made mercury; and antimony and available for widespread platinum (Aitchison 1960). domestic and commercial Aitchison further noted that application (Aitchison 1960). the pseudo-science of alchemy, The steam engine, improved upon based upon the Aristotelian by Watt in 1781, opened the way principles and beliefs for a huge expansion in the concerning the origin of development of mechanical matter, provided the basis of power. Aitchison further knowledge concerning the suggests that the outstanding extraction of metals and other metallurgical development of elements. Modern chemical the early 19th century did not concepts, upon which our occur in that science, but was present knowledge of metals is the result of a vast increase based, did not become an in the development and accepted science until at least application of mechanical two hundred years later. This power. This development limited knowledge of chemistry resulted in a tremendous

Page 374 magnification of the scale of development as the greatest work, an increase in the size purely metallurgical advance in of plant and furnace the one hundred years from 1850 facilities, the sum of which to 1950 (Dennis 1963). was an overall higher Although steel was known in productive efficiency. World early times and its use in the copper production figures bear fine blades of Damascus is this out: 1810, 9100 metric legendary, the carbon content tons; 1870, 159,000 metric of those early was tons. British figures highly variable and unevenly show a similar trend: 113,400 distributed. World production metric tons at the beginning of of steel in 1850 amounted to no the 19th century, increasing to more than 59,900 metric tons 2,268,000 metric tons by 1850 per year {Aitchison 1960). {Aitchison 1960). Cast and were used almost exclusively in By 1850, the knowledge of construction at that time metals had progressed in a (Aitchison 1960, Dennis 1963). similar fashion. Some 39 Mild steel, a low carbon additional metals had been product, was not known in 1850. discovered since Agricola's But following the processing time, though not necessarily developments of Bessemer and isolated into their free or Kelley, together with Siemen•s pure form. These included open hearth process that came arsenic, , cobalt, nickel, about ten years later, the molybdenum, tungsten, uranium, ability to produce large chromium and others. Some 23 quantities of uniform quality more would become known in the steel was attained by the next fifty years: vanadium, latter 1880's (Dennis 1963). potassium, sodium, barium, Dennis further suggests that calcium and aluminum being these three developments in among the more commonly known steel making were the in today's everyday usage foundation upon which the Age {Aitchison 1960). of steel was established and which brought so many The 19th century was a time subsequent developments which of many discoveries a~d dramatically influenced inventions which laid the industry (Dennis 1963). foundation for much of the 20th century's social and economic The rapid strides in the use needs. It could be argued of iron.and steel, once these endlessly which discovery or processes were refined, brought invention was the most about great increases in the critical, but the independent demands for other metals, discoveries made by Henry particularly copper, tin and Bessemer of England, and lead. Not only was this William Kelley, a Kentucky expressed as a demand for ironmaster, can be considered greater production of known among the most important. metals, but also as a demand These individuals ushered in for a greater variety of the "Age of steel" with their metals. Aluminum, a metal steel-making processes almost unknown in the mid-19th developed between 1850 and century, experienced 1855. Some credit this astronomical growth during the

Page 375 first half of the twentieth mines, the slag from the century following the nearly smelters and the tailings from simultaneous developments in the fine grinding of 1886 by Heroult of France and concentration increased Hall of the United States. exponentially as new Their application of technologies were developed for electrolytic ·refining extracting the metals from ores principles for reducing bauxite of ever decreasing grade or ores to alumina was the purity. catalyst. (See Table I.)

TABLE I

WORLD PRODUCTION OF SOME NON-FERROUS METALS (Dennis 1963) Production (Metric Tons)

Metal 1850 1875 1900 1950 1960 19891

Copper 50,000 118,235 476,000 2,289,000 4,164,000 7,100,000 Lead 118,235 290,300 771,100 1,518,620 2,322,380 2,572,000 Zinc 14,970 149,685 435,450 1,650,160 3,184,200 5,130,000 Tin 16,300 32,650 77,110 146,963 163,020 152,000 Nickel 450 7,250 166,000 324,770 574,900 Aiuminum 6,620 1,420,640 4,544,970 14,295,000 Uranium(U308 ) 37,300 42,085

1Engineering and Mining Journal, 121st Annual Survey and Outlook, MacLean Hunter Publishing Co., Chicago, Illinois, Vol. 191 No. 3, March, 1990.

Whatever conclusion is drawn Contemporary Concentracting regarding the critical turning Methodologies point in metallurgical development, be it mechanical The importance of power, advancements in concentrating the metal content chemistry, the steel making of ores prior to smelting or process or electrical power, it refining to the pure form becomes clear that the 19th cannot be overemphasized. Ore century was, at the least, a consists of a complex of most dynamic period in the disseminated through advancement of the arts and barren rock material known as sciences upon which modern gangue. Elimination of as much society and civilization is of the gangue as possible based. With this growth in before smelting is an economic knowledge and demand for necessity in order to save metals, came a corresponding transportation costs from mill growth in mining for metallic to smelter and to reduce the ores and in the processing of unnecessary costs and these ores into useful metals. complications caused by the Likewise, the quantity of waste gangue in the smelting and products from this growth refining process (Agricola increased. Waste rock from the 1550, Richards and Locke 1940, Aitchison 1960, Dennis 1963).

Page 376 For thousands of years, the uses steel balls as a grinding crushing of ore to a small or medium. Hardinge improved the fine particle size has been the design in 1908 by key to liberating the most giving the cylinder a conical amount of metal. From hand shape that is able to provide mortars and pestles through the greater control of the final various man and animal powered product size (Dennis 1963). grinding mills such as the arrastra and Chilean Wheel, to The ball mill quickly the water and steam powered replaced stamp mills where stamp mills, man has endeavored cyanidation had been adopted to improve upon the grinding for gold ore concentration. process. The latter half of However, it was not popular in the 19th century saw the most mills that continued to use recent development in ore mercury amalgamation because crushing technology, brought the tumbling action of the about by two of the major balls would flour the mercury, breakthroughs of that period, rendering it useless. The rod steel and electricity. mill was invented to resolve this problem. It is similar in Today, grinding is performed size and shape to the tube mill by machinery that had its and employs a charge of steel origins in the 1880s. The rods as long as the inside predecessor of the modern chamber of the mill to achieve milling machines was the short- the grinding (Young 1976). lived barrel pulverizer, made of iron and invented in England Grinding of the ore into fine in 1880. It was quickly particles and the use of replaced by the tube mill, a mercury for gold amalgamation, long, cylindrical steel as we have seen, are processes container with a hard flint used since early times to interior lining. It was the liberate the greatest amount of first successful modern metal possible from the gangue grinding machine. Pebble-sized or host rock. The use of ore is fed into the tube and mercury for amalgamation of grinding is achieved by silver ores was not known until tumbling the ore pebbles as the about the middle of th(;! 15th tube rotates. Hard, durable century. Developed initially rock pebbles such as flint may in the silver mines of Spain, also be added as a grinding this procedure was extensively medium. Tube mills may also be used in Mexico by the divided into two or more Conquistadors upon the compartments by screens to discovery of local mercury facilitate particle size sources. It was a most control. The tube mill found effective process for the oxide great favor in the South ores of silver, but as these African gold fields in 1904 to sources rapidly diminished and further grind stamp mill more and more of the mines went products. deeper than the weathered zones near the surface and The ball mill was encountered the sulfide ores introduced in 1885 and is also below the water table, it was a rotating cylinder, but of found that the costs of greater width than length. It extracting the silver by the

Page 377. normal smelting processes of treat the slimes and now nearly the day became prohibitive. all ore is finely ground to the The was developed slime fraction (Dennis 1961). to offset this problem. It employed a copper-iron-sulfate Cyanidation, in the first ten product added to mercury years of its use, made every amalgamated silver sulfide ore. gold mill and milling practice The ore, mercury, copper-iron- then in use nearly obsolete. sulfate and salt amalgamate This method replaced mercury would be washed in water-filled amalgamation and opened the vats. The amalgam would be door for large volume fine- retained while the gangue would grinding and the new be washed away (Young 1976). opportunities for greater metal After 1850, a chlorine gas recovery from lower grades of process was introduced that ore (Young 1976). Nearly every gained considerable use in tailings heap from previous silver ore beneficiation gold washing activities in the (Aitchison 1960). Mercury world was reworked with the amalgamation, with salt and a cyanide process to recover the few other reagents such as metal values lost in the previously described, coupled previous milling practices with gravity separation by (Young 1976). The resulting washing, remained the principal impact of this tailings method of ore reworking activity was a gold concentration up to the late boom as big as the rush to the nineteenth century. However, Yukon or to Wittwatersrand in as late as the 1850s, most of South Africa (Young 1976). the world's total gold supply came from placer mining, and in The introduction and each of the new fields such as development of the flotation California, Yukon and process during the period 1893 Australia, the metal was won by to 1902 for concentrating metal the washing of gravels and values from ore proved to be of alluvial deposits (Aitchison major significance to 1960). metallurgical science (Rickard 1932). The basic principle is All this changed with the simple; when vigorously introduction of the cyanide agitated with a mixture of leach process. It was first water, oily substances and used in New Zealand in 1889 and bubbles of air, the metal- was introduced to the gold bearing particles become coated fields of South Africa a year with oil, attach themselves to later (Aitchison 1960). Its the bubbles which rise to the initial application was for the surface and are floated off recovery of residual gold into collectors. The gangue contained in tailings. At sinks and is discarded as first, only the coarser sized tailings (Aitchison 1960, "sand" particles could be Dennis 1963). The flotation effectively treated by process is effective for only cyanidation, and the fine sized one metal. However, by adding particles, or "slimes," had to additional flotation circuits, be separated for treatment or complex ores containing two or discarded. In time, methods more metals can be treated were developed to effectively allowing each metal to be

Page 378 recovered instead of discarded contained 0.62 percent copper, with the tailings. those from a flotation process installed a year later had a copper content of 0.15 percent, Flotation became widely used or one fourth that of the in the non-ferrous metal gravity method. The increased industry after 1910, and may be recovery of copper as a result considered the salvation of the of flotation amounted to copper industry in the western 24,947,800 kilograms per year United States. Up until the with no change in ore grade or development of flotation, ores tonnage put through the mills of less than 2 percent copper (Rickard 1932). were very difficult to process (Young 1976). In spite of Another example of copper flotation's widespread success recovery as a result of both and application in the mineral fine grinding and flotation can industry, cyanidation is still be found in the reprocessing of the more favored method for stamp mill tailings deposited precious metal concentration in the 1860s in the Upper (Young 1976). Peninsula of Michigan. It was estimated that there was as Present iron technologies much as a 25 percent loss of (blast furnaces) require lump copper in the early stamp mill forms of feed stock and the process. These tailings were finely ground concentrates from reprocessed during the period flotation are not acceptable. 1916 through 1952 by modern However, . the advent of grinding mills, with pelletizing., briquetting and ammonia and flotation. The scintering:techniques for iron recovery of copper amounted to concentrates to achieve the some 266,798,500 kilograms over necessary large particle feed a thirty-six year period stocks has made the benefits of (Stevens 1972). flotation available to the iron and steel making industry Other forms of mineral (Dennis 1963) • The first concentration are also commercial all-flotation iron noteworthy. Water-gravity ore concentrating mill was put separation, as we have seen, into service in Michigan in has been practiced since time 1954 (Dennis 1967). immemorial, and the methods of washing ores have been only Rickard (1932) provides an slightly improved during all indication of the efficiency of this time. Major gravity the flotation process in separation methods, which still mineral value recovery with an find · considerable use today, example of copper content in include a variety of tables tailings before and after a over which a water and finely flotation circuit was installed ground ore product flow, some by the Anaconda Copper Mining of which have riffles to trap Company in Montana. The ore in the heavier particles, most of both cases had a copper content which have a mechanical of 3 percent and was subjected movement or jigging action to to the same milling processes. assist in the gravity Tailings generated from a separation of ore from gangue water-gravity separation method (Dennis 1963). A major

Page ·379 addition was made to gravity Mill And Tailings Production separation in 1891 with the development of sink-float With the developments in the technology. This process is metallurgical technologies that based upon adjusting the took place in the latter half specific gravity of the of the 19th and first quarter floating medium. An early of the 20th centuries firmly application of this method was established, it is now the addition of sand to appropriate to examine examples increase the specific gravity of mineral production, and in of water for separating coal, turn, tailings. An account of which floats off, from slate, the Comstock silver district of shale and clay, which is Nevada noted that in October, heavier than the sand-water, 1859, Hastings and Woodward had and sinks. This process, with two water-powered at various materials used as a work which reduced 4. 5 metric heavy media, is widely used tons of ore per day (DeQuille today in concentrating 1889). In August of 1860, a and coal processing (Dennis nine-stamp portable battery had 1963). been set up and dry ore production was one ton per day, Magnetic separation was first but wet crushing increased developed in Sweden in 1883. production to 9 metric tons As the name suggests, it has a from the Bowers Mine (Rickard very wide application in the 1932). On August 11, 1860, processing of magnetic iron A.B. Paul started a stamp mill ores such as magnetite, in the district and the first franklinite and lot of ore to be milled was 4.5 (Dennis 1963) . Electrostatic metric tons of tailings from separation, developed in the the Gold Hill arras tras United States in 1901, is based (Rickard 1932). Rickard also .on the principle that minerals noted that metal recovery will take on an electrical during the early days of the charge if brought into contact Comstock was only 60 to 65 with a source charged at a high percent, but by 1867, potential. The readiness and retreatment using settling degree of the charge varies tanks or by concentration with the mineral (Dennis 1963). increased recovery up to 85 This process has been useful in percent. the separation of many minerals including zinc blende from In contrast to the relatively , from low daily tonnages of ore molybdenite, from milling in the Comstock and ilmenite, titanium recovery District in the mid 1800s, a and the separation of the tin gold operation in Alaska was mineral from processing 10,650 metric tons columbite (Dennis 1963). of ore per day in 1930, using gravity separation and The waste products from these flotation. Of this production, mineral concentrating processes are discarded as tailings.

Page 380 5013 metric tons was waste other minerals including rock, 5613 tons went to bauxite, gold, silver, lead, tailings and 6 tons was a lead- titanium, diatomite, feldspar, gold-silver concentrate sands and gravels, salt and (Rickard 1932). talc. Uranium and other radioactive metals were not During the early 1930s; the included in these tailings Anaconda Copper Mining Company production figures (PEDCO concentrator in Montana had a 1984) • mill capacity of 10,900 metric tons per day. Of this daily Tailings Disposal production, 8830 metric tons, or 81 percent was discarded as Little has been written of tailings while only 2070 metric the disposal of the waste tons of concentrate was products of mines and mills. produced; 599 metric tons of Agricola, describing a washing copper was recovered from the process for tinstone, stated concentrate. The grade of the that 11 ••• the mud mixed with the mill feed stock was 5.5 percent very fine tinstone ••. which has copper (Richards and Locke neither settled in the large 194 0) • settling pit nor in the transverse launder •.. flows away A mill in Miami, Arizona, may and settles in the bed of a be more representative of stream or river. 11 (Agricola copper recovery and tailings 1550). Hoover and Hoover noted production of a late twentieth in their translation of century operation where low Agricola that before a stamp grade ores are the rule. In mill had been installed in 1930, this.mill had a capacity Joachimsthal (Czechoslovakia) of 15,400 :metric tons per day in 1521, a great many metal of o. 716 percent copper ore; bearing particles were left in 98.3 percent of the daily the washed sands " ..• which had production, or 14,140 metric been either thrown away or used tons, was tailings (Richards as mortar for building ..•. " and Locke 1940). (Hoover and Hoover in Agricola 1912). some of the more recent Some fifty years later, tot11l historical accounts confirm United states copper tailings that tailings, as a rule, were production was about discarded from the mill to go 218,360,000 metric tons per as they would in their own way. year. Tailings produced in DeQuille notes that in the 1981 from other mineral Comstock silver district of 11 processing activities in the Nevada in the 1860s, ••• untold United states included millions (of dollars) in gold, phosphate (155,128,000 metric silver and quicksilver were tons), iron (145,149,000 metric swept away into the Carson tons) and molybdenum River with the tailings .... 11 (27,578,270 metric tons). (DeQuille 1889). In early These figures amount to 87 practice, tailings were percent of the tailings frequently dumped into nearby produced, the remaining lakes, rivers or the sea, or 52,523,000 metric tons coming were placed in dumps and piles from the recovery and where the solid material processing of some twenty five accumulated and the water ran

Page 381 to waste (Lindgren 1909, and Development 1981) . Perhaps Richards and Locke 1940, Kelly the most common use of tailings and Spottiswood 1982). These is for the backfilling of practices continued until underground mines after removal recent times in the United of the ores when there is States and elsewhere as little likelihood that evidenced by reports of recoverable ore values remain. tailings control activities in In most cases, the tailings are Idaho in 1968 and South Dakota separated, the coarse or sand in 1973 (Matthew 1973, Williams fractions being used for the 1973, Kelly and Spottiswood backfill and the fine fractions 1982) . or slimes going to tailings ponds or otherwise discarded Tailings accumulations have (Kelly and Spottiswood 1982). been recognized for their Lindgren noted as early as potential as sources of 1909, while commenting upon the additional mineral resources. loss of mineral values in ore We have seen in earlier concentration, that the discussions that tailings confinement and storage of accumulations were reworked to tailings should be regulated by recover gold and silver values governmental agencies in order with the coming of the stamp to minimize such losses in mills to the Comstock district minerals. As an accompanying of Nevada; to recover copper side thought, he noted that from stamp mill tailings with confinement of tailings would the advent of fine grinding, also be desirable in order to leaching, and flotation in avoid contamination of the Michigan; and the reworking of water supply (Lindgren 1909). nearly every previous tailings heap to recover gold after the The practice of tailings cyanidation process was confinement as a specific and developed. Other minerals may distinct part of the mineral be recovered from tailings beneficiation process appears deposits in addition to the to have started in the very minerals that initially late 19th century and gained produced the tailings. rapid acceptance through the Tailings produced from porphyry first half of the 20th century. ore bodies frequently contain The Anaconda Copper Mining appreciable amounts of Company's concentrator at potassium and phosphorous. Anaconda, Montana initiated a Tailings from some copper and tailings confinement practice gold ores have been reprocessed sometime in the late 1890s to recover radioactive and (Richmond and Sjogren 1972). other heavy metal values (Bean Although the general literature 1973) . Also, as previously is silent regarding the noted, tailings have been used initiation and specific for mortar as early as 1521 in purposes of tailings Europe. They have been used, confinement, a conclusion may or have the potential for use, be drawn that this practice had in such areas as railroad its origins with the ballast, agricultural uses, spectacular developments in road building and other metallurgical extraction construction materials (Bean techniques that occurred at 1973, Mountain States Research that time: fine grinding,

Page 382 chlorination, cyanidation and Today, there are tailings flotation. These developments deposits, large and small, old demonstrated that significant and new, active and inactive changes in technology may all over the world. Many of likely result in today's waste these deposits or accumulations becoming tomorrow's "gold are residual from the earliest mine. 11 The urgings of Lindgren milling activities and are to store tailings for possible still to be found in rivers, future mineral recovery and the along the shores of lakes or as observations of Bean and others discrete piles among the that tailings accumulations are remnants of historic mining and potential mineral storehouses milling operations. Others, support the conclusion that the especially those laid down confinement and discrete after the middle of the 20th storage of tailings was brought century, are mostly in the form about in anticipation of future qf discrete confinements. mineral value recovery. In summary, man has always Other considerations that been engaged in the search and undoubtably made a major extraction of the earth's contribution to the practice of minerals. At first, man's tailings confinement included needs were few, but as more the need to conserve and knowledge was gained, needs recycle process water, became greater and more especially in arid regions complex. We have seen that up where water is scarce, and for until about 150 years ago, our the control of water pollution needs were comparatively few (Lindgren 1909, Richards and and the demand made of the Locke 1940, Kelly and m i n e r a 1 r e s o u r c e Spottiswood 1982). Richards correspondingly small. With and Locke -noted in 1940 that the breakthroughs in knowledge 11 ••• so many of the Western that have occurred since, states have passed antidebris especially the understanding of legislation aimed against the chemistry and the industrial pollution of streams by the developments that occurred introduction of mill tailing, during the latter half of the or slime. 11 The Anaconda 19th and first half of the 20th Company first built ponds centuries, the growth of the specifically for water world's increasingly technical pollution control near Warm civilization has made Springs, Montana in 1910. · tremendous demands for those This, and subsequent ponds mineral products of the earth. added in 1913 and 1957, were As mining and milling practices for the· treatment of acid have responded to meet these waters discharged from the needs, greater quantities of mines and mills in Butte, mineral ores of ever decreasing several miles upstream. These purity have been utilized, ponds would occasionally resulting in an ever increasing receive and store tailings growth of tailings and other which would be washed down associated waste products. At Silver Bow Creek during first, the disposal of mineral emergency situations (Richmond waste was of little or no and Sjogren 1972). consequence. As the volumes of these waste products increased,

Page 383 and more people became Proceedings of the First affected, their disposal became International Tailing of greater concern. once Symposium. Miller Freeman confinement of tailings became Publications, Inc. San a general practice, additional Francisco, California. problems became apparent. The stabilization of tailings Dean, Karl c., Havens, against wind and water erosion Richard and Glantz, M.W. and the return of lands to 1974. Methods and Costs for productive uses have long been stabilizing Fine Sized two of these concerns. Efforts Mineral Wastes. Bureau of to address and resolve these Mines Report of concerns have been documented Investigations, RI 7896. since the 1950s. More recent United States Department of concerns such as heavy metal the Interior. Washington, contamination and it~ D.C. associated health risks have become apparent only within the Dennis, W.H. 1961. last two or three decades as Metallurgy in the Service of detection technologies and Man. Macdonald. London. modern health science knowledge have emerged to identify and Dennis, W.H. 1963. understand them. A Hundred Years of Metallurgy. Gerald As mankind continues to move Duckworth and Co., Ltd. from a survival lifestyle to London. one dependent upon technology, new products and technologies Dennis, W.H. 1967. will be developed to satisfy Foundations of Iron and the growing needs. With the Steel Metallurgy. Elsevier new products will come new Publishing Co. , Ltd. problems and with new problems Amsterdam, London, New York. will come new solutions. DeQuille, Dan (William Literature Cited Wright) • 1889. A History of the Comstock Silver Lode Agricola, Georgius. and Mines. Reprint of 1889 1550. De Re Metallica. edition. Promontory Press. Translated by Herbert Clark New York. 1974. Hoover and Lou Henry Hoover. Dover Publications, Inc. New Hoover, Herbert Clark and York. 1950. Hoover, Lou Henry. 1912, Ln De Re Metallica. Footnotes Aitchison, Leslie. 1960. A to translation. Dover History of Metals. Publications, Inc. New York. Volume II. Interscience 1950. Publishers, Inc. New York. Kelly, Errol G. and Spottiswood, David J. 1982. Bean, James J. 1973. Introduction to Mineral Tailing As An Orebody. Processing. John Wiley and p. 606-614. In Alpin, C.L. Sons. New York, Charleston, and George o. Argall, Jr. Brisbane, Toronto, (ed) Tailing Disposal Today: Singapore.

Page_ 384 Lindgren, Waldemar. Richards, Robert H. and 1909. Resources of the Locke, Charles. 1940. United States in Gold, Textbook of Ore Silver, Copper, Lead and Dressing, Third Edition. Zinc. In on the McGraw-Hill Book co. New Conservation of Mineral York and London. Resources. Bulletin 394. Department of the Interior. Rickard, T.A. 1932. A United States Geological History of American Mining. Survey. Washington, D.C. McGraw-Hill Book Co., Inc. New York and London. Matthew, Floyd L. 1973. Pros and Cons of combined Richmond, Timothy c. and Treatment of Mining and Sjogren, C.A. 1972. Domestic Waste. p. 700-713. Stabilization of In Alpin, C.L. and George Concentrator Tailings o. Argall, Jr. (ed) Tailing in the Vicinity of Anaconda, Disposal Today: Proceedings Montana. Environmental of the First International Engineering Department. Tailing Symposium. Miller The Anaconda Company. Freeman Publications, Inc. Tucson, Arizona. San Francisco, California. Stevens, Larry. 1972. Mountain states Research Unpublished remarks at and Development, Inc. Minerals Waste stabilization 1981. Inventory of Waste Liaison Committee Meeting. Embankments of surface and Houghton, Michigan. Underground Openings; May 23, 1972. Metal/Nonmetal Active Mines. United states Department of Thrush, Paul W. 1968. A the Interior. Bureau of Dictionary of Mining, Mines 'Research Contract Mineral and Related Terms. Report. Washington, D.C. United States Department of the Interior. Bureau of PEDCO Environmental, Inc. Mines. Washington, 1984. Evaluation of Management Practices Williams, Roy E. 1973. for Mine Solid waste Modernization of Coeur Storage, Disposal and d'Alene Tailings Disposal Treatment. Draft Final Practices. p. 634-673. In Report. Vol. III. Alp in, C. L. and George o. Evaluation of the Argall, Jr. (ed) Tailing Effectiveness of Waste Disposal Today: Proceedings Management Practices. of the First International United states Environmental Tailing Symposium. Miller Protection Agency. Freeman Publications, Inc. Cincinnati, Ohio. San Francisco, California. Poss, John R. 1975. Young, Otis E., Jr. Stones of Destiny. 1976. Western Mining. Michigan Technological Second Printing. University University. Houghton, of Oklahoma Press. Norman, Michigan. Oklahoma.

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