112 ' Marine Minerals: Exploring Our New Ocean Frontier 



straints. Such areas include New York, Boston, Los 

 Angeles, San Francisco, San Juan, and Honolulu. 



Garnet 



Garnet is an iron-aluminum silicate used for 

 high-quality abrasives and as filter media. Its size 

 and shape in its natural form is important in de- 

 termining its industrial use. The United States is 

 the dominant world producer and user of garnet, 

 accounting for about 75 percent of the world's out- 

 put and 70 percent of its consumption. In 1986, 

 the U.S. produced about 35,000 tons of garnet and 

 consumed about 28,000 tons.'°^ Domestic demand 

 is expected to rise only modestly to about 38,000 

 tons per year by 2000. '"* World resources are very 

 large and distributed widely among nations. 



Monazite 



Monazite is a rare-earth and thorium mineral 

 found in association with heavy mineral sands. It 

 is recovered mainly as a byproduct of processing 

 titanium and zirconium minerals, principally in 

 Australia and India. Domestic production of 

 monazite is small relative to demand. As a result, 

 the United States imports monazite concentrates 

 and intermediates, primarily for their rare-earth 

 content. 



The rare earths are used domestically in a wide 

 variety of end uses including: petroleum fluid crack- 

 ing catalysts, metallurgical applications in high- 

 strength low-alloy steels, phosphors used in color 

 television and color computer displays, high- 

 strength permanent magnets, laser crystals for high- 

 energy applications such as fusion research and spe- 

 cial underwater-to-surface communications, elec- 

 tronic components, high-tech ceramics, fiber-optics, 

 and superconductors. It is estimated that about 

 15,400 tons of equivalent rare-earth oxides were 

 consumed domestically in 1986.'"^ 



Substitutes for the rare earths are available for 

 many applications, but are usually much less ef- 

 fective. The United States imported 3,262 tons of 

 monazite concentrates in 1986, representing about 

 12 percent of the total estimated domestic consump- 

 tion of equivalent rare-earth oxides. 



World resources of the rare-earth elements are 

 large, and critical shortages of most of the elements 

 are not likely to occur. Because domestic demand 

 for thorium is small, only a small amount of the 

 thorium available in monazite is recovered. It is 

 used in aerospace alloys, lamp mantles, welding 

 electrodes, high-temperature refractory applica- 

 tions, and nuclear fuel. 



Zircon 



Zircon is recovered as a byproduct from the ex- 

 traction of titanium minerals from titaneous sands. 

 Zirconium metal is used as fuel cladding and struc- 

 tural material in nuclear reactors and for chemical 

 processing equipment because of its resistance to 

 corrosion. Ferrozirconium; zircon and zirconium 

 oxide, is used in abrasives, refractories, and cer- 

 amics. Zircon is produced in the United States with 

 about 40 to 50 percent of consumption imported 

 frorii Australia, South Africa, and France. 



Domestic consumption of contained zirconium 

 was about 50,000 tons in 1983. '«« The United States 

 is estimated to have about 14 million tons of zir- 

 con, primarily associated with titaneous sand de- 

 posits. It is expected that domestic contained zir- 

 conium demand may reach about 1 16,000 tons by 

 2000, an annual growth of nearly 6 percent. Sub- 

 stitutes for zirconium are available, but at a sacri- 

 fice in effectiveness. Domestic reserves are gauged 

 to be adequate for some time in the future although 

 the United States imports much of that consumed 

 from cheaper sources. 



'°'G. Austin, "Garnet, Industrial," Mineral Commodity Sum- 

 manes— ;987 (Washington, DC: U.S. Bureau of Mines, 1986), p. 56. 



'"J. Smoalt, "Garnet," Mineral Faces and Problems — 1985 Edi- 

 tion, Bulletin 675 (Washington, DC; U.S. Bureau of Mines, 1986), 

 p. 297. 



'"'J. Hedrick, "Rare-Earth Metals," Mineral Commodity Sum- 

 maries— 1987 {Washington, DC: U.S. Bureau of Mines, 1986), p. 126. 



io6yy Adams, "Zirconium and Hafnium," Mineral Facts and Prob- 

 lems— 1985 Edition, Bulletin 675 (Washington, DC: U.S. Bureau of 

 Mines, 1986), p. 941. 



