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Guanajuato.-District de Guanajuato, Mineral y Municipality de Guanajuato, El Nopal, El Obrero, Sierra de Santa Rosa (mines), Mineral del Calvillo, Bismute (mine).

Guerrero.-District de Alarcon, Mineral y Municipality de Taxco; Municipality de Tehuilotepec, Tehuilotepec (mine).

Jalisco. Canton de Ahualulco, Town y Mineral de Hostotipaquillo.
Mexico.-District de Sultepec, San Pedro mine.

Puebla.-District de Tetela, Mineral y Municipality de Tetela del Oro.
Queretaro.-District de Cadereyta de Mendez, Municipality y Mineral del

Doctor.

San Luis Potosi.-District de Catorce, Rancho Salado. District de Guadalcazar, Municipality y Mineral de Guadalcazar. District de Santa Maria del Rio, Municipality Reyes, Cerro de la Piedra del Molino, Hacienda, San Pedro. District de Tancanhuitz, Arroyo de las Papas.

Zacatecas.-District de Mazapil, Municipality y Mineral de Mazapil, San Jose mine. District de Sombrerete, Mineral y Municipality de Chalchihuites, Santa Maria Dolores mine. District de Zacatecas, Municipality y Mineral de Zacatecas, Las Cantera mine.

Most Mexican deposits now known are apparently in the southern or south central part of Mexico and far inland. Shipment into the United States would therefore entail a very long haul or a combination of a long land haul with a long water haul. Furthermore, most of the deposits seem to be far from a railroad and at least part of them contain barite. No information is now available to suggest that any important part of the consuming needs of the United States can be supplied from Mexican deposits.

CENTRAL AMERICA

GUATEMALA

Fluorspar has been found in Guatemala in the departments of Baja Verapaz and El Quiché and elsewhere in the Republic, but very little is known regarding the quality, composition, or extent of the deposits. There is no fluorspar production, no local consumption, no imports, and no exports.

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Fluorspar occurs in Argentina at San Roque in the Province of Cordoba in fissure veins from 8 to 12 inches wide to lodes several yards wide in biotite gneiss and associated with pegmatites. This fluorspar occurs in the gneisses east of their contact with the granite massif of the Andes. The deposits are reported as large and pure.

87 See Miller, B. L., and Singewald, J. T., Mineral Deposits of South America. New York, 1919, p. 54; also Beck, Richard, tr. by Weed, W. H., The Nature of Ore Deposits. New York, 1905, p. 218.

The fluorspar occurs in bands that range from colorless, light green, yellow, violet, and blue, to almost black. The associated minerals are quartz, feldspar, muscovite, pyrite, and chalcedony.

BOLIVIA

Fluorspar is reported to occur in very small quantities at several places in Bolivia, but none is mined or exported. Even if the deposits were of commercial size, high transportation costs to the coast would probably preclude profitable operation. There are no imports and no consumption of fluorspar in Bolivia.

BRAZIL

Deposits of fluorspar are reported to exist in the State of Minas Geraes, but none has been mined and no information is available on the extent of the deposits. In mining limestone near Palmyra in the southern part of Minas Geraes a small amount of fluorspar is obtained by a by-product. This small quantity seems to be enough for local needs, as there are no imports. Local fluorspar consumption is insignificant. A small amount is used in a glass plant in Rio de Janeiro.

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England stands second only to the United States as a fluorspar producing country; in recent years these two countries together have produced around 80 per cent of the world's fluorspar output. Before 1901 England's fluorspar production averaged less than 1,500 long tons per year, but gradually the production increased to a maximum of over 65,000 long tons in 1917. Since 1917 it has varied from 23,000 to 55,000 long tons per year. Before 1910 much of the British production was exported to the United States. In 1910, such exports amounted to about 62 per cent of the British production; in 1911, 53 per cent; 1912, 49 per cent; 1913, 37 per cent; 1914, 27 per cent; 1915, 19 per cent; 1916, 20 per cent; 1917, 17 per cent; 1918, 20.5 per cent; 1919, 14.5 per cent; and 1920, 27 per cent; 1921, 6 per cent; 1922, 65 per cent; 1923, 40 per cent; and 1924, 58 per cent. Some fluorspar is exported to Canada and formerly a little to Russia, but the United States has always been the largest

38 The most complete recent account of fluorspar in Great Britain is given by Carruthers, R. G., Pocock, R. W., Wray, D. A., and others, Fluorspar: Spec. Repts., Min. Res. Great Britain, Geol. Survey Mem., vol. 4, 1916, 38 pp. (2d. ed., 1917).

See also Imperial Mineral Resources Bureau (London), Fluorspar (1913-1919): 1921, 18 pp.

Wedd, C. B., and Drabble, G. C., "The fluorspar deposits of Derbyshire": Trans. Inst. Min. Eng., vol. 34, 1908, pp. 501-535.

66

The Engineer (London), Fluorspar "; Aug. 21, 1908, pp. 185 and 187.

customer. Exports evidently declined steadily until about 1917, while British home consumption increased steadily. Since 1917, business conditions have been so unstable that the present trend is not clear. In 1918 British officials estimated that normal fluorspar consumption in the United Kingdom was about 35,000 long tons per year.

From 1906-7 for about 10 years, much of the British production came from the reworking of tailings and waste dumps at old lead mines, principally in Derbyshire. It was reported in 1916, however, that these dumps were nearly exhausted and could not be depended upon for any large future tonnage. From available information production from this source in the past few years seems to have been relatively small.

Fluorspar deposits in Great Britain are centered in Derbyshire, Durham (north of England) including adjacent parts of Northumberland, Yorkshire, and Cumberland, Cornwall, and North Wales (Flintshire). Of these districts only the first two have much importance. Derbyshire has usually been the larger producer, but a large part of this production for a number of years came from reworking waste piles rather than from new mining operations. The following descriptions of the principal districts in Great Britain are given by Carruthers, Pocock, and Wray,39

DERBYSHIRE

In Derbyshire, the oldest and best known fluorspar center in Britain, the mineral occurs in filling vein fissures and other cavities in the Carboniferous limestone. A description of the veins has been given in an earlier publication,1o and parts of the following accounts have been reproduced from it. Fluorspar has also been recently studied by Wedd and Drabble 11 and their work with that of Egglestone is the source of much information.42

Fluorspar is found in comparatively few of the rake veins that traverse the Derbyshire lime. Wedd and Drabble say that it is practically confined to the limestone and does not pass up into the overlying grits and shales; moreover, it is restricted to the uppermost 600 feet of the limestone, mainly in the uppermost 300 or 400 feet. This restriction confines the occurrences to the margin of the limestone massif; inward from the margin and at depth the spar is

30 See footnote 37.

40 Green, A. H., Foster, C. Le N., and Dakyns, J. R., The Geology of the Carboniferous Limestone, Yoredale Rocks, and Millstone Grit of North Derbyshire: Mem. Geol. Survey Great Britain, 2d ed., 1887, 228 pp.

41 Wedd, C. B., and Drabble, G. Cooper., "The fluorspar deposits of Derbyshire": Trans. Inst. Min. Eng., vol. 35, 1908, pp. 501-535.

42 Egglestone, W. M., "The occurrence and commercial uses of fluorspar": Trans. Inst. Min. Eng., vol. 35, 1908, p. 236.

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replaced by barytes and calcite. They noticed, moreover, that practically all the fluorspar comes from the eastern margin of the massif, and from the Crich and Ashover inliers beyond; little is found along the western fringe.

The massive commercial Derbyshire fluorspar is usually opaque white or faintly tinted; the well-grown cubes found in cavities are more highly colored, ranging from amber yellow to deep violet. Green, pink, and pure blue tints are noticeably absent, although "ruby-colored fluor in perfect cubes" has been recorded. A variety peculiar to the county is known as "blue John "; it is strictly local and is used solely for ornamental work. The spar is associated with barytes, calcite, and galena, and sometimes with blende, but only locally with copper ores; the metallic minerals are often concentrated in the center of the vein. The rarity of quartz is noteworthy.

Most fluorspar, both lump and gravel, is used for fluxing in iron and steel foundries. Fluorspar from Ashover is said to be in demand for refining silver and gold. Fine-ground spar is used for making hydrofluoric acid; the finest quality makes a pure white enamel glaze for pottery, especially for lavatory ware. The product of Stubbin Low or Smith's mine near Bonsall caters to this demand. Derbyshire fluorspar is usually put on the market in two grades— lump spar, which is the mine-run product, and gravel spar, or tailings from the old ore dressings, which contains from 55 to 75 per cent CaF. The lump spar has some impurities, including calcite and barytes, and when dressed for market averages from 90 to 95 per cent of CaF.

Near Matlock and at Ashover a third grade, fine-ground fluorspar is now being produced by grinding good lump spar in a ball mill.

All mines were originally worked for lead, the fluorspar being a by-product of no commercial value, but its increasing use in smelting and other industries has caused reopening of certain mines where much fluorspar had been stored in the "gob" of the old workings.

As both fluorspar and lead can now be marketed and as the price of the latter has advanced over its former low level, prospects for the profitable working of the Derbyshire mines are promising.

Wedd and Drabble believe that the available supply of fluorspar is almost intact and can bear the strain of greatly increased annual output for many years. The surface waste heaps which have been the mainstay of the Derbyshire output for the last six years have now been well picked over, and are no longer an important source of supplies.

The fluorspar deposits of Derbyshire are found in the Castleton, Bradwell, Eyam, Calver, Matlock, Ashover, and Crich districts.

DURHAM

Although fluorspar is common in the metalliferous veins of the north of England, the commercially productive area is restricted, and the whole supply now comes from the upper part of Weardale.

Upper Weardale, from Stanhope to the western watershed, covers 80 to 90 square miles. All this ground is occupied by Carboniferous strata, mostly Yoredale rocks, composed of numerous alternations of sandstone, shale, and limestone in beds up to 100 feet thick. The dip is gentle and the outcrops wind in and out of the valleys regularly.

The district is an old lead-mining center, although the industry is not conducted on the old-time scale. Fluorspar mining is a comparatively new feature, having been started in earnest less than 20 years ago. The first record for Durham in the home office "Returns of Mines," was in 1883, when the Weardale Iron and Coal Co. (Ltd.) produced 13 tons of spar from the Red vein (probably the Crawley mine). The next year that company mined 109 tons; and from 1898 the output increased rapidly. The veins are abundant, of the normal fissure type, mostly filling small faults, and oriented in two groups, one trending southwest, the other between east and southeast. When traversing beds of limestone the veins frequently give off horizontal stringers or "flats" similar in content to the veins themselves.

In this district fluorspar is the chief constituent of veins and "flats" alike; sometimes it fills the whole vein, and spar bodies measuring as much as 20 feet across have been found. Galena, although often scattered in small quantities through the spar, is generally concentrated in the center of the vein. Some veins carry chalybite instead of galena; then the fluor not infrequently occupies the center of the vein, the iron minerals being in the walls and impregnating the country rock.

Weardale fluor is generally pale, usually an amethyst tint, although white or clear varieties are also common; green or yellow spar is rare, and red quite absent. The fluorspar is well crystallized and rarely granular, and the crystals are large.

Quartz, the commonest accessory mineral, is found in relatively small quantities, often lining geodes or cavities. Chalybite and isolated crystals of galena are not uncommon and are usually concen trated in the center of the vein. Pyrites is rare, and in contrast with the Derbyshire and Kentucky deposits there is an entire absence of barytes. The only other accessory mineral of any importance is cal

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