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UNITED STATES

The Rosiclare vein in southern Illinois has supplied a very large proportion of the total past production of the United States. The known productive areas of this vein have been adequately explored to a depth of 350 feet, in places as deep as 620 feet. Most workable ore above the 350-foot level has been extracted and ample evidence shows that the ore bodies are getting shorter and narrower, with longer "pinches " between separate bodies; therefore this vein probably can not be depended upon to supply the bulk of the domestic fluorspar production for many more years.

Although there are some other deposits in Illinois, such as the Daisy mine and the new Argo mine near Rosiclare, which probably will be important producers for several years to come, production from present known deposits in Illinois will no doubt decline appreciably within a comparatively few years.

The western Kentucky deposits have not been as thoroughly prospected, and the best of the present known veins have not been worked or even explored to any great depth. It is probably safe to assume, however, that most of the easily found deposits have been discovered and that much of the easily accessible surface ore has been removed. Future mining must go deeper and the larger deposits be worked more systematically if they are to supply any large proportion of the domestic production.

The present known deposits in Kentucky may, perhaps, be relied upon to yield important quantities of fluorspar for some time to come, and the Kentucky field will probably outlive the Illinois field. Nevertheless, when the latter reserves are exhausted and Kentucky is called upon to supply the bulk of the domestic fluorspar requirements, the reserves can not be expected to last many years unless consumption decreases or new deposits are found.

The only known deposit which is at all comparable with the Rosiclare, Daisy, Blue Diggings, or Tabb veins of the Illinois-Kentucky district is that at Wagon Wheel Gap, Colo. This deposit can probably be relied upon to supply western markets for a considerable period. No other districts in the United States are important enough from present indications of known deposits to be considered as possessing important reserves.

The fluorspar consumption of the United States will probably continue to increase. Even at the present rate of consumption the known domestic fluorspar reserves will not last many years. It is unwise to hazard a guess as to the extent of such reserves, but within 20 years or perhaps much sooner domestic deposits may be unable to supply our needs, unless large new deposits are discovered, con

sumption decreases, or imports fill a larger proportion of our demands.

The World War showed that fluorspar is a necessary mineral, and domestic producers should be encouraged to develop as large reserves "as possible and to work narrow veins even at great depths. Although this country may be able to import considerable fluorspar temporarily, we do not know that our domestic needs could be supplied for any length of time from foreign deposits.

FOREIGN COUNTRIES

More information is available on the fluorspar resources of Great Britain than of any other foreign country, but no definite estimates of total reserves have been made. Moreover, reports are conflicting, for some observers state that reserves are very large and will last many years, while others have expressed almost opposite views. It is evident, however, that most of the old mine dumps which have supplied so much of the British production in the past are now practically exhausted, that future production must come largely from actual mining operations, and that British fluorspar consumption is apparently increasing.

Germany is now a fairly important producer, but little is known of her reserves. In the past, however, German fluorspar consumption has required nearly all of the domestic production. It is prob ably safe to assume that when normal conditions are restored Germany will not have any large exportable surplus of fluorspar.

Italy, France, Canada, and South Africa (Transvaal) have fluorspar deposits which will probably continue to supply moderate amounts for some time to come. For example, Italy reports that one deposit contains about 200,000 tons of sure ore and 200,000 tons more of probable ore. In comparison with the annual consumption of fluorspar throughout the world these resources are insignificant, but the deposit is important, for the fluorspar is of high grade.

Important fluorspar deposits may be developed in a number of other countries-Mexico, for example-but no dependence can be placed upon such possibilities.

CONCLUSIONS

Present knowledge of the world's fluorspar resources indicates that few districts can produce any very large tonnage. Some of these districts probably have already passed their period of maximum production. Consumption is increasing and new deposits are not being developed rapidly enough to maintain production at its present rate.

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Our resources should be carefully conserved by working narrow and low-grade veins in depth, by minimizing losses in milling, and by the most efficient utilization of fluorspar for all purposes. Το carry out the first two suggestions the market price of fluorspar must be high enough to give the producers a profit commensurate▾ with the risk involved.

MINERALOGY

COMPOSITION

Fluorspar or fluorite is calcium fluoride (CaF2) and consists theoretically of 51.1 per cent of calcium (Ca) and 48.9 per cent fluorine (F). A large body of fluorspar analyzing more than 99 per cent CaF, is rarely found, and by far the largest proportion of the mineral shipped contains only 80 to 85 per cent of calcium fluoride. Most commercial fluorspar contains silica or calcite, or both, and usually some iron oxide and alumina. Other more or less common associated minerals are barite, galena, and sphalerite. The following table illustrates the variations in composition of fluorspar:

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1. Rosiclare district, Ill., washed gravel spar, average shipments, 1912, analyses by Colorado Fuel & Iron Co.

2. Noyes mine, Madoc, Ontario, Canada. Average of 16 carload shipments. Analysis by Algoma Steel Corporation.

3. Deming district, N. Mex. Car shipment. 4. Jamestown district, Colo. Car shipment.

Analysis by Colorado Fuel & Iron Co.
Analysis by Colorado Fuel & Iron Co.

5. Wagon Wheel Gap, Colo. Analysis quoted by Aurand, H. A., Fluorspar Deposits of Colorado: Colorado Geol. Survey Bull. 18, 1920, p. 78.

6. Tonuco, N. Mex., gravel spar. Analysis by L. A. Stewart, Fairview Fluorspar & Lead Co. 7. High Lost mine, Matlock Bath, Derbyshire, England, selected lump spar. Trans. Inst. Min. Eng. (England), 1908, vol. 35, p. 13. 8. North Gate, Colo., picked specimen. Analysis by L. A. Stewart, Fairview Fluorspar & Lead Co.

Most of the fluorspar shipped, particularly the grade used as a flux for steel, has been concentrated. Thus the analyses given for marketed products represent adjustment of grade by mechanical means to meet specifications.

GENERAL DESCRIPTION AND NOMENCLATURE

Fluorspar is a moderately hard, glassy mineral, transparent or translucent, crystallizing in the isometric system, usually in cubes. The crystals have good octahedral cleavage and perfect octahedra may be easily cleaved out. The mineral commonly occurs in crystal

line masses and often in well-formed crystals; less often in granular form. It has a wide range of color. In large deposits white and gray fluorspar are probably the most common. In narrower veins, and often in well-crystallized deposits in siliceous rocks, green and purple fluorspars are common, particularly near the surface. Other colors seen more or less frequently are blue, yellow, orange, red, pink, brown, and black. The causes of this variation in color are not known.

Hardness: 4. Specific gravity: 3.01 to 3.25. Melting point: 1,270 to 1,387° C. About 900° C. is also given, but probably represents impure material. Index of refraction: 1.434. Color: White, gray, green, purple, blue, yellow, red, pink, brown, black, and colorless. Streak: Usually white, but pinkish in all purple varieties. Luster: Vitreous, dull, or earthy when the mineral is granular; rarely submetallic. Cleavage: Octahedral, good. Fracture: Conchoidal to splintery. Transparency: Transparent or translucent to nearly opaque. Tenacity: Brittle. Most fluorspar decrepitates or flies apart when heated.

Fluorspar from some localities shows phosphorescence, especially after moderate heating; that is, it emits a characteristic glow in the dark after the exciting cause or agent has been removed. Some specimens also show fluorescence, which resembles phosphorescence except that the glow continues only during exposure to the exciting cause; this cause may be sunlight, electrical discharges, or Röntgen rays.

The term fluorite, which is now probably in widest use in works on mineralogy, seems to suggest the pure mineral, but in commercial practice the name fluorspar is used almost exclusively. The fluorspar of commerce always contains impurities, such as silica and calcite. In England it is called fluorspar or fluor, or sometimes, locally, Derbyshire spar, or blue John (local variety). In the United States the earliest references were to "fluate of lime."

In some places the term "spar" is often used, especially by miners, to denote fluorspar, and it is used in this report where there is no danger of confusion. But, as "spar" is also applied to denote barite (heavy spar), feldspar, calc-spar (calcite), gypsum, and even quartz, the term should be used carefully.

Color alone is not ordinarily a good indication of the purity of fluorspar, but experience often shows that in particular districts color may be used as a guide. Thus, in the mills using ore from the Rosiclare vein in Illinois, acid grade, as well as glass and enameling grades of fluorspar, is made by sorting from a picking belt. For acid grade only the transparent, white, or very light tints of gray, blue, and green are picked. For glass and enamel slightly darker

shades are picked, but the material must be clear and nearly transparent; dark brown and deep purple fluorspar is rejected. Near North Gate, Colo., however, a specimen of deep-green ore was selected which analyzed 99.49 per cent CaF, and therefore was of excellent grade for acid.

STRUCTURE

Fluorspar differs in structure. In commercial deposits it occurs most commonly as a coarsely crystalline vein filling, which may be homogeneous and of uniform color, or may show bands of different colors. The structure that ranks next in importance is distinct crystals, either individuals or aggregates of intergrown and twinned crystals. Crystals are usually found partly filling cavities or along sides of underground watercourses, but occasionally they are found in residual clay that has formed by the weathering of the rocks that originally held the crystals. Less commonly, fluorspar has a bedded structure. The best examples of this structure are the bedded deposits near Cave in Rock, Ill. The structure of some deposits closely resembles that of a loosely coherent sandstone. In the Jamestown (Colo.) district most of the fluorspar occurs as a medium to coarsely granular aggregate that resembles porous sandstone. At Beatty, Nev., the typical ore is much finer in texture and ranges from loosely coherent to pulverulent.

At Wagon Wheel Gap much of the ore is white, hard, and has a structure closely resembling that of a very fine-grained white marble or perhaps a hard, white, finely crystalline barite.

In the western Kentucky district much of the residual ore formed by weathering is a loose to partly coherent coarse gravel, in places very pure (as at the Yandell and Liberty Bond and Watson mines) and in places mixed with clay. It is locally known as "gravel" fluorspar.

A columnar or even an almost fibrous structure is sometimes observed. A cavernous or porous structure is common in the Madoc (Ontario) district and is occasionally found elsewhere, as in western Kentucky.

ASSOCIATED MINERALS

The nature and the relative proportions of the minerals associated with fluorspar are of importance. The mode of association is equally important, for upon this depends the ease of separation or even the possibility of separation at a profit.

Calcite or calcium carbonate is perhaps the most common gangue material in the large commercial deposits, particularly that in the Illinois-Kentucky field. It occurs both in the crystalline form and as limestone of various degrees of purity. Its specific gravity (2.7)

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