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Acid-grade fluorspar should contain a minimum of 97 percent CaF, and most specifications contain limitations on SiO2, CaCO3, and sulfide sulfur.

Chemical and physical requirements of acid-grade fluorspar are set forth in National Stockpile Material Purchase Specifications P-69a, dated February 13, 1952, by Defense Materials Service, General Services Administration.

National Stockpile Purchase Specification P-69b-R, dated May 22, 1957, contains requirements for metallurgical-grade fluorspar being acquired by the Defense Materials Services of General Services Administration for the stockpile. Technology

Geology. In the Illinois-Kentucky district the country rock is limestone, shale, and sandstone. Fluorspar occurs as veins along faults ranging in thickness from a mere film to a width of more than 30 feet and in extensive flat-lying replacement-type deposits in limestone. Residual deposits resulting from weathering of fluorite-bearing veins also are fairly common in the district and often indicate the presence of vein deposits at greater depth (4) (26) (27).2

In the Western States fluorspar occurs under a wide variety of conditions— as fillings in fractures and shear zones forming more or less well-defined veins and as replacements in the country rock. Much occurs in igneous formations (3) (9) (10) (20) (22) (23) (24).

At Ivigtut, Greenland, the cryolite is associated with pegmatite within an intrusive mass of porphyritic granite. Associated minerals are silica, fluorspar, galena, pyrite and siderite (16).

Mining.-Fluorspar mining is, in many respects, similar to the mining of metalliferous deposits in steeply dipping veins or in flat lying deposits. Mining is done by shafts, drifts, and opencuts.

Shaft mines differ greatly in size, capacity, methods of working, and efficiency. At prospect shafts not over 50 feet deep the simplest mining method may be employed with little other hoisting equipment than a hand-operated windlass and and a bucket. At small mines more than 50 feet deep single-compartment shafts with wood headframes are used; the ore is loaded at the face and trammed by hand on narrow-gauge tracks to the shaft, through which it is hoisted by singledrum hoists powered by gasoline engines.

At larger mines the main shafts usually include two hoisting compartments and a manway compartment containing a ladder, air and water pipes, and electric-power conduits. Steel headframes generally have been adopted, and hoisting is done with double-drum hoists with skips or cages. Mining methods follow the practice of metal mines, adopting the method best suited to conditions. Top slicing, cut-and-fi'l, and shrinkage and open stoping are among the methods commonly used. Bedded deposits are usually worked by a room-and-pillar system. Some of the larger mines are extensively mechanized, using diesel-powered hauling and loading equipment (1) (17) (21).

At many fluorspar mines water pumping is a major element in the mining operation. Large quantities of water enter the mines in the Illinois-Kentucky district through channels in the limestone and from the Ohio River. At the Rosiclare mine for example, the flow of underground water into it was at a rate of 7,000 gallons per minute. The Crystal mine in the Cave-in-Rock area in Illinois has a water problem. When the "Big Sink," a landlocked area covering about 800 acres, rises to a high level because of excessive rains, water seeps into the mine from innumerable underground crevices and fissures and causes it to flood.

Milling.-Although some domestic fluorspar is sold with little or no processing after mining, most crude ore requires beneficiation to yield a finished product. Milling practices range from rather simple methods, such as hand sorting, washing, screening, and gravity separation by jigs and tables, to sink-float and a frothflotation processes. Most of the domestic output is produced by sink-float, flotation, or a combination. These processes permit utilization of lower grade ore; recovery is much more efficient and the finished product of higher quality. Also, the flotation process permits recovery of the lead and zinc minerals often associated with the fluorspar ores (1) (7) (27).

To a large extent the selection of a milling process depends on the character of ore to be treated and the type of product desired. Some highly disseminated ores can be treated successfully only by flotation, since fine grinding is necessary to liberate the component particles. Flotation also is commonly used where a pure product of fine particle size is desired, such as ceramic and acid-grade

2 Figures in parentheses refer to items in the bibliography at the end of this exhibit.

fluorspar (18) (29). The heavy-medium or sink-float process is usually employed where a coarse product, such as metallurgical-grade gravel is desired and enough concentration can be achieved without fine grinding (15). Some producers use both processes in combination, producing gravel products by sinkfloat and treating undersize from the heavy-medium mill by flotation or using sink-float to produce a preconcentrate, which is then used as feed for the flotation plant (5) (6). Flotation concentrates are pelletized at one mill for use as metallurgical fluorspar (14).

Flotation and other mineral-dressing techniques are employed to treat cryolite. Chemical processes are used to recover fluorine from phosphate rock. At present the greater part recovered is in the acidulation step in the production of ordinary superphosphate. The fluosilicic acid is sold or used to prepare salts such as sodium silicofluoride and ammonium, magnesium, and zinc fluosilicates. A small tonnage of fluorine in the form of synthetic fluorspar was recovered by the Tennessee Valley Authority from stack gases evolved in processing phosphate rock. The recovery process consists in absorbing the fluorine, which is present as hydrogen fluoride, in a bed of lump limestone at temperatures above the dewpoint of the stack gases. The calcium fluoride reaction product separates from the limestone lumps in the form of fines; portions of the bed are withdrawn from the tower at intervals and screened to remove the fines, and the oversize (partly reacted limestone) is recycled to the tower with fresh limestone (11) (12) (13). Uses

Fluorine is used principally in the form of fluorspar, cryolite, hydrofluoric acid and fluosilicates.

Until recently the largest use of fluorspar has been as a flux in the manufacture of basic open-hearth, basic electric furnace and Bessemer steel. Many other metallurgical operations including the production of iron castings, ferroalloys, and nickel and its alloys; the melting and casting of aluminum and magnesium; the smelting of secondary metals; and the manufacture of fluxing compounds utilize small tonnages of fluorspar. Metallurgical operations consume fluorspar in gravel form and flotation concentrates have been utilized to a very limited degree. The use of pelletized flotation concentrates has not attained wide acceptance in the metallurgical industries, and this seriously limits the market for flotation concentrates of subacid grade.

The second major use has been in the production of hydrofluoric acid, an essential raw material in the manufacture of synthetic cryolite, and aluminum fluoride for the aluminum industry and in many other applications in the chemical industry. In 1956 consumption of fluorspar in the production of hydrofluoric acid exceeded that used in the production of steel. Acid-grade spar requirements of the aluminum industry have expanded rapidly in recent years, paralleling the expansion in aluminum production. Cryolite, which serves as an electrolyte in the electrolytic reduction of alumina, is required in large quantities to fill reduction cells when new aluminum-production units are started; and in regular reduction operations cryolite consumed must be replaced by additional cryolite or aluminum fluoride. Based on 1951 data, it was estimated that 47 pounds of eryolite and 58 pounds of aluminum fluoride were consumed per ton of virgin aluminum produced. The largest use of cryolite is in the production of aluminum. Smaller quantities are used in abrasives, insecticides, glass, and enamel.

Hydrofluoric acid is used by industry as a source of fluorine for the production of refrigerants and propellants, the fluorocarbon plastics and other fluorine compounds; as a catalyst in the prduction of high-octane aviation fuels; in etching and polishing glass, pickling steel, cleaning metal castings, and enamel stripping; as a laboratory reagent; and for many other industrial uses. An important use for hydrofluoric acid is in the field of atomic energy. Its use here is to produce uranium tetrafluoride from uranium oxide, the raw material, and is itself used in the preparation of uranium hexafluoride. The most volatile compound of uranium, uranium hexafluoride, has been extensively utilized in the separation of uranium isotopes by thermal diffusion.

The third major use of fluorspar is for ceramic purposes in the manufacture of opal and flint container glass and as an ingredient in enamels for coating steel and cast iron. Ceramic-grade material also is consumed for welding-rod coatings, fiber-glass production and as an additive to brick clays.

Small quantities of ceramic or acid-grade fluorspar also are consumed by the magnesium industry.

Small quantities of clean, virtually colorless, and flawless crystalline fluorspar have been used in lenses or prisms of microscopes, telescopes, and spectroscopes, but synthetically grown crystals have largely displaced fluorite in these uses.

Markets for the fluosilicates are relatively limited. Fluosilicic acid is used as a disinfectant in the brewing industry, as a preservative in electroplating, as a concrete hardener, and in the manufacture of silicofluoride salts. Sodium silicofluoride is used for fluorination of community water supplies. Sodium silicofluo ride and ammonium fluosilicate are used in insecticides, laundry applications, fluxing, ceramics, and casting light metals. The magnesium and zinc fluosilicates are used as concrete hardeners and the magnesium salt also finds application in magnesium foundries.

Byproducts and coproducts

Lead and zinc and minor quantities of other metals, such as silver, cadmium, and germanium, are often recovered as byproducts or coproducts of fluorspar. The value of lead and zinc produced in the Illinois-Kentucky area in recent years has been substantial. These byproducts are important factors in the economy of many fluorspar operations.

Substitutes

During World War II topaz, ilmenite, aluminum dross, and salt were studied as substitutes for metallurgical-grade fluorspar, but none were as effective. Bauxite has been used as a flux in the open-hearth steel plant at Port Kembla. Australia; and, although it was cheaper, it was only about one-third as effective as fluorspar. In the past several years the production of a special flux, employing fluorspar as a base, has increased somewhat; and many iron foundries that formerly used fluorspar alone are now using this flux.

The petroleum industry has two alkylation processes for producing high-octane components for gasoline; one uses hydrofluoric acid and the other sulfuric acid. The sulfuric acid process can be used in place of the hydrofluoric acid process, however, the equipment for one acid process does not readily lend itself to the use of the other acid.

At present there is no satisfactory substitute for fluorspar in the manufacture of hydrofluoric acid.

Synthetics

The bulk of the cryolite consumed in the United States is in the form of synthetic cryolite made by reacting sodium aluminate with hydrogen fluoride obtained from acid-grade fluorspar.

Secondary sources and recovery

At some aluminum plants fluorine compounds are recovered and reused in the aluminum-reduction process. This practice is growing and is expected to become an increasingly important factor in the market.

Several thousand tons of concentrates are recovered annually in the IllinoisKentucky district from waste dumps of earlier mill operations.

Reserves

Fluorspar reserves in the United States were recently estimated by the United States Geological Survey at 22.5 million short tons containing more than 35 percent CaF, or the equivalent value in combined fluorspar and metallic sulfides (8). About 61 percent of the 22.5 million tons was measured and indicated ore and the remainder inferred ore. An additional 12 million tons of lower grade material containing 15 to 35 percent CaF2 was estimated. These reserve figures are larger than previous estimates made by the United States Geological Survey because better reserve information is now available and substantial quantities of ore have been found in the last few years.

Presently known reserves could support mine production for 30 years at the 1951-55 rate of about 750,000 tons of crude ore annually.

Although recovery from many of the lower grade deposits is not economically feasible at the present time, the presence of other valuable minerals and factors such as advantageous geographic location and favorable mining conditions, have made it possible to mine some deposits containing less than 30 percent CaF2.

The geographic distribution of the higher grade reserves, expressed in terms of crude ore, is shown in table 2. In general the major reserves are concentrated in the major producing districts, the Illinois-Kentucky district accounting for about 54 percent.

TABLE 2.-Estimated reserves of higher grade1 fluorspar in the United States as of October 1956, by regions, expressed in terms of short tons of crude ore

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There are very large reserves of fluorspar in many foreign countries, notably Mexico, Canada, Germany, Italy, Spain, and southwest Africa; but statistics on them are sketchy or unavailable. Total North American reserves are extensive. Mexico, the leading foreign supplier, is believed to have major reserves of high quality ore. Recent discoveries in Coahuila and Chihuahua of large numbers of additional deposits are evidence of the abundance of fluorspar in northern Mexico. Reserves in Newfoundland have been estimated by some investigators at several million tons (16).

Reserves of crude fluorspar containing more than 35 percent CaF2 in Western Europe have been estimated at 13,200,000 short tons, while reserves in the Soviet Union and its satellites may exceed 5.5 million short tons. The bulk of western European reserves are said to be in Italy, Western Germany, Spain, and the United Kingdom (19).

The United States has enormous reserves of phosphate rock-at least 13 million long tons-and some authorities have estimated its fluorine content to be equivalent to about 900 million tons of fluorspar. However, recovery of this fluorine or any part of it depends upon the quantity of phosphate rock mined and sold, upon the treatment processes to which the phosphate rock is subjected, and upon further development of methods of recovering the fluorine in the desired commercial forms.

No estimate of the cryolite reserves in Greenland is available, but recent reports indicate that exploration has failed to develop appreciable new reserves, and the deposit may be approaching depletion.

Sources and adequacy of statistical information on the commodity

Annual and quarterly data on production and shipments of fluorspar are obtained from domestic producers by the Bureau of Mines. Over 95 percent of the consumers of all grades of fluorspar are canvassed quarterly. A biennal consumer canvass covers virtually 100 percent of the known consumption. known importers of fluorspar are canvassed annually for imports and sales by quantity and use.

All

As difficulty has been encountered in determining fluorspar grade and use patterns, changes recently have been made in the canvass to obtain more nearly complete and accurate information. In the consumption canvass data is being obtained on the grade of fluorspar-acid, ceramic, or metallurgical-being consumed in specific industries. In the canvassing of steel plants and iron foundries which is done by the Bureau of the Census, similar detail by grade is not obtained. A truer picture of fluorspar consumption could be presented if this detail were available.

Changes in the producers canvass provided a more positive picture on the grade of ore being mined, processed in the mills, and the grade of finished product being shipped to consumers.

There is a lack of statistical information on the recovery of byproduct flourine from phosphate rock processing plants and secondary fluorine recovery at aluminum reduction plants.

World production and trade data are compiled by the Division of Foreign Activities, Bureau of Mines. United States exports and imports are obtained from the Department of Commerce.

Production, consumption, and foreign trade

The growth of the fluorspar industry in the United States during the present century has been rapid, particularly since 1941. Production increased from an annual average of about 40,000 short tons in the decade 1900-09, to an average of about 323,000 tons during the decade 1940-49. During the same period, average annual imports increased from about 15,000 tons to 57,000 tons. From 1950 to 1956 domestic production has fluctuated from 347,000 tons in 1951 to a low of 245,000 tons in 1954.

Domestic fluorspar production in 1956 (shipments from mines and mills) totaled 329,719 short tons. Of this Illinois contributed 178,254; Montana 59,775; Kentucky 14,865; Utah 10,581; and Nevada, Colorado, and Tennessee together 66,244. As a whole domestic fluorspar has been supplying a declining fraction of the market in recent years. Difficulty in meeting specifications required by buyers and the competition of foreign fluorspar are among the factors which have influenced trends in the industry.

In recent years imports have been greatly stimulated by the strong demands of the consuming industries, and the requirements of the national stockpile. Imports, since 1952, have exceeded domestic production and in 1956 a new high of 490,742 short tons was recorded. Mexico supplied about one-half of the total fluorspar imported. Canada, Germany, Italy, and Spain supplied all but a small part of the remainder. European fluorspar generally enters at Philadelphia; Canadian at Buffalo, Cleveland, New York, and Philadelphia; and the Mexican at Douglas, Ariz., and Brownsville, Eagle Pass, El Paso, and Marathon, Tex. Imports, by country of origin, for 1947-51 (average), 1952-56, are shown in table 3.

As a means of maintaining domestic production capacity, in July 1956, Congress passed Public Law 733 authorizing the Department of the Interior to purchase four strategic minerals, including acid-grade fluorspar from domestic mines for stockpiling. The General Services Administration was authorized by Interior to purchase 250,000 short dry tons of newly mined domestic acidgrade fluorspar at a price of $53 per short dry ton by December 31, 1958. The program made slow progress at first, but after the specifications were modified in January 1957, the volume of purchases increased. The Commodity Credit Corporation of the Department of Agriculture is currently engaged in exchanging 100,000 tons of surplus wheat for Mexican fluorspar under terms of an agreement of June 1955. This fluorspar is also being purchased and stockpiled by the General Services Administration.

TABLE 3.-Fluorspar imports in 1947-51 (average) and 1952-56, by countries [In short tons]

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Consumption of fluorspar in the United States has been increasing rapidly, principally as a result of growth in the requirements of the steel and aluminum industries, and increased use of fluorine chemicals. Consumption statistics by uses and geographic regions are shown in tables 4 and 5.

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