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A journal article, with some attention to both theoretical and practical considerations, reviewed techniques and equipment types for reducing mine-run mineral materials to the particle-size ranges in which they can serve the needs of industry, or, conversely, for agglomerating those too finely divided for advantageous utilization. Kyanite was one of the minerals for which grindability indices and other grinding information were cited.6 Subsequent articles by the same author summarized details of various processes that are applicable for the separation and concentration of specific industrial minerals, one of which was kyanite. Procedures discussed in relation to kyanite ore treatment included gravity separation by tabling, electromagnetic separation, and froth flotation.7

Kyanite can be used as an alternative ingredient to replace tabular alumina and alpha quartz in a patented composition for the production of fused alumina refractories.8 Calcined kyanite, mixed with asbestos, iron powder, lead, lead sulfide, petroleum coke, and other substances, is used in the manufacture of composite friction elements, according to a recent foreign patent. Kyanite, tabular alumina, calcined alumina, kaolin, and asbestos or glass fiber are the materials specified in a patent to be compounded with water and phosphoric acid for the manufacture of alu

mina refractories of the ramming-mix type that are highly resistant to abrasion and to temperatures in excess of 2000° F.10

Mullite and various types of mullite refractories can be produced by firing a dry mixture of aluminum chlorohydroxide and silica in a process for which a patent was issued.11 A method was patented according to which granular mullite or other specified granular materials can be compacted by high-pressure impact compression to form molded shapes suitable for firing to produce very dense, highly refractory articles.12

4 Prior, H. David, and Arthur J. Metzger. A Bond for Mullite Refractories (abstract). Ceram. Bull., v. 50, No. 9, September 1971, p. 802.

Smith, Peter C., and Robert E. Moore. High Temperature Compressive Creep of Mullite (abstract). Ceram. Bull., v. 50, No. 9, September 1971, pp. 803–804.

5 Davis, E. G., and G. V. Sullivan. Recovery of Heavy Minerals From Sand and Gravel Operations in the Southeastern United States. BuMines Rept. of Inv. 7517, 1971, 25 pp.

Llewellyn, Thomas O., and James S. Browning. Continuous Heavy Liquid Concentration of Kyanite. BuMines Rept. of Inv. 7481, 1971, 11 pp. 6 Jones, G. K. Size Reduction and Size Enlargement. Industrial Minerals (London), No. 47, August 1971, pp. 33-43.

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Jones, G. K. Concentration of Minerals by Sizes and Gravity. Separating Minerals by Froth Flotation, Electrical Properties, and Other Methods. Industrial Minerals (London), No. 49, October 1971, pp. 43-50; No. 51, December 1971, pp. 3941.

8 Drever, J. R., P. D. Zimmerman, and A. B. Brink (assigned to Amsted Industries, Chicago, Ill.). Composition for Making Refractory Articles. U.S. Pat. 3,567,473, Mar. 2, 1971.

Griffith, A. M. (assigned to Abex Corp.). British Pat. 1,236,218, June 23, 1971.

10 Salazar, P. V. (assigned to Nalco Chemical Co.). Canadian Pat. 879,143, Aug. 24, 1971.

11 Albert, R. E. (assigned to E. I. du Pont de Nemours & Co., Wilmington, Del.). Process for the Preparation of Mullite Bonded Refractory Materials. U.S. Pat. 3,615,778, Oct. 26, 1971.

12 Star, S., J. A. Waterman, and A. M. Daniel (assigned to Israel Mining Industries, Institute for Research & Development). British Pat. 1,217,267, Dec. 31, 1970.

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World production of lead in 1971 declined from the record level of 1970, but as lead consumption increased an improved supply-demand relationship was achieved. Free world mine production decreased about 3 percent as production gains in Canada, the United States, and Mexico were not sufficient to offset losses in other countries. An increase of about 2 percent in metal consumption was accompanied by a significant decline in metal inventories, particularly in the United States.

Free world producer stocks of lead declined about 79,000 tons during the year to about 224,000 tons at yearend. The improved supply-demand relationship was the principal factor tending to stabilize market price. A modest increase in the New York price of lead was achieved in the second half of the year. The London Metal Exchange (LME) quotation remained relatively stable during the first 7 months of 1971, but declined sharply following imposition of the surcharge on U.S. imports on August 15, 1971. After the duty surcharge was removed in December the LME price began to rise.

The domestic lead industry achieved increases in both mine production and consumption of lead, but production of primary refined metal declined owing to the sharp reduction in imports of crude materials for processing in domestic plants. Mine production increased 1 percent to 578,600 tons as gains in Missouri, Idaho, and Colorado more than offset the decline in Utah's output. Primary lead production from both domestic and foreign sources was nearly 2 percent less than the record high level achieved in 1970. Domestic mines contributed 88 percent of the total primary metal. Secondary lead output of 596,800 tons, representing about 40 percent of the market supply, was only slightly less

than the 1970 output. The domestic supply of lead-primary, secondary, and imports— amounted to 1.46 million tons, 6,000 tons less than in 1970.

Demand for lead for use in transportation continued to grow as requirements for the major component, batteries, increased 15 percent; however, antiknock requirements declined 5 percent below the record level of 1970. Ammunition requirements increased substantially, but the quantity of lead used in pigments decreased. Total consumption of lead was 1.43 million tons, 71,000 tons more than in 1970. Battery use amounted to 47 percent of the total and gasoline additives, 18 percent.

Primary metal stocks declined in every month during 1971 except January and July. From an inventory of 97,900 tons at the beginning of the year metal stocks were reduced to 51,800 tons at yearend. Commercial sales from the Government stockpile again were insignificant, with only 12 tons sold and shipped. Transfers to Government plant uses amounted to 9,600 tons. The available domestic supply from all sources indicated an apparent consumption of 85,000 tons of lead in addition to the reported consumption of 1.43 million

tons.

The world price of lead, as indicated by the LME monthly average, in terms of U.S. currency, ranged between 11.92 cents and 12.23 cents per pound during the first 6 months, then declined to 10.04 cents in November, and moved up to 10.47 cents in December. The average for the year was 11.52 cents. The domestic price for common lead at New York held at 13.50 cents per pound until June 23, when a price range of 14 to 142 cents was established which held through mid-December, when a split

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price of 14.0 to 14.3 cents was established for delivery anywhere in the United States. The New York price averaged 13.89 cents for the year.

At yearend, International Smelting and Refining Co. closed its custom lead smelter at Tooele, Utah, and U.S. Smelting, Refining and Mining Co. closed down its U.S. and Lark mine and Midvale mill.

Legislation and Government Programs. The program of the Office of Minerals Exploration, Geological Survey, U.S. Department of the Interior, continued in effect but activity was minimal. Lead was withdrawn from the list of eligible metals in June 1962 and there was virtually no activity in connection with any previous certified projects involving lead.

Sales of Government surplus lead from the strategic stockpile to commercial users under Public Law 91-46 dropped to 12 tons from 22 tons sold in 1970. Lead authorized for sale on an off-the-shelf basis to commercial users was 77,290 tons at yearend 1971. Transfers for Government use in 1971 under Public Law 89-9 amounted to 9,572 tons used primarily at Government-owned ammunition plants. The remaining tonnage in the authorization was 21,683 at yearend. Actual drawdown of Government stock during 1971 was 13,180 tons, leaving a total of 1,127,440 tons remaining in the stockpile, of which 597,440 tons was in excess of the 530,000-ton stockpile objective.

In February legislation was introduced in the Congress to dispose of 498,000 tons of surplus lead in Government stocks. Hearings were held but further action was delayed pending determination of methods of disposal.

A bill (H.R. 8587) to provide an adequate supply of lead and zinc for consump

tion in the United States from domestic and foreign sources was introduced in May and referred to the Committee on Ways and Means. The proposed legislation was designed to implement, with respect to lead and zinc, the National Mining and Minerals policy (Public Law 91-631), but no further action was taken.

The International Lead and Zinc Study Group convened in Torremolinos, Spain,

Nov. 2-6, 1971, to review the current situation and outlook for 1972 for lead and zinc. The forecasts for 1971 production and consumption of lead made at the 14th Session were reduced and a supply surplus of 53,000 tons was anticipated. For 1972, lead mine production was forecast to increase by 107,000 tons (4 percent) and lead metal production was forecast to increase 151,000 tons (5 percent) over 1971 levels. Lead metal consumption was predicted to exceed the 1971 level by 63,000 tons, 2 percent more than in 1971. The Study Group also discussed trade liberalization and the need to adopt policies designed to promote the orderly development of the lead and zinc industry throughout the world. Special groups were designated to continue investigations of specific supply-demand problems identified in the discussions and to submit recommendations for their alleviation to the Standing Committee.

The International Lead-Zinc Research Organization continued to sponsor a broad program of research on lead and lead compounds and to publish information on their applications including batteries, architectural uses, and cable sheathing. The Organization also described research on properties including corrosion resistance of lead and its alloys, preparation and uses of lead compounds, lead pigments in paints, and lead compounds in ceramics.

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Figure 1.-Trends in the lead industry in the United States.

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