Bureau of Mines / Minerals yearbook: Metals, minerals, and fuels 1972
Year 1972, Volume 1 (1972)
Wells, J. Robert
Kyanite and related materials, pp. 689-693 ff. PDF (598.6 KB)
689Kyanite and Related Minerals By J. Robert Wells1 Kyanite, andalusite, and sillimanite are anhydrous aluminum silicate minerals that are closely akin in both composition and use patterns and have the same chemical formula, Al205.Si02. Closely related materials include synthetic mullite, dumortierite, and topaz, also classed as aluminum silicates. The latter two additionally contain boron and fluorine, respectively. All of these substances have the capability of serving as materials for the manufacture of special-duty refractories of the high-alumina category. There has been no record in recent years, however, of significant utilization of either dumortierite or topaz for this purpose in the United States. Although not enough statistics are published to be wholly conclusive, it appears that the United States, India, and the Republic of South Africa hold :the lead among world producers of kyanite-group minerals and that they may be not far from evenly matched in that regard. Presumably, the U.S.S.R. and some other industrialized nations also produce significant quantities of these materials. Domestic production of kyanite plus synthetic mullite dipped moderately in tonnage in 1972, the first such downturn since 1968. Total value of these two materials, which showed a steep drop in 1971 from the peak reached in 1970, sagged again in 1972, though less sharply. These declines may have resulted from the slackness In shipments of finished brick and shape kyanite-mullite refractories that was noted in the 1971 Minerals Yearbook chapter, a trend that was even more marked in 1972. Total value of shipments of mullite brick and shapes made predominately of kyanite-group minerals or synthetic mullite (exclusive of molten-cast products) was 10% lower in 1971 and 28% lower in 1972 than in 1970. Mullite-based mortars, ramming mixes, and castable refractories presumably held up well, because total value of all nonclay refractories followed a 6% decline in 1971 with a 12% increase in 1972.2 In ample compensation for any reduction in domestic consumption of the mullite refractories, exports of kyanite and allied materials scored a spectacular increase in 1972 with regard to both quantity and total value. Kyanite imports, meanwhile, fell to their lowest level in over 30 years. Legislation and Government Programs. —The 1970 revision of the list of strategic materials for stockpiling excluded kyanitemullite. At that time Government holdings totaled approximately 4,800 short tons of that commodity, and Congress authorized the stepwise disposal of the entire quantity by public sale. Notices dated November 23, 1971, January 19, 1972, June 27, 1972, and October 27, 1972, invited bids for the as-is sale of portions of this material, but no acceptable offers were received. The Office of Minerals Exploration offered to grant Government loans up to 50% of approved costs for the exploration of eligible kyanite deposits, but no loans for that purpose were made in 1972. 1 Physical scientist, Division of Nonmetallic Minerals. 2 u~s~ Department of Commerce, Bureau of the Census. Current Industrial Reports, Series: MQ—32C; Summary for 1971; First, Second, Third, and Fourth Quarters 1972.
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