ZIRCONIUM AND HAFNIUM 



719 



Table 160. — General range of zirconium-hafnium ratios in 

 zircon frotn igneous rocks 



[Data from Chessex and Delaloye, 1965: Fleischer, 1965; Gottfried and 

 Waring, 1964; Hess, 1962; Lyakhovich and Shevaleyevskii, 1962; Vainshtein 

 and others, 1959] 



Rock type 



Zr-Hf 



Gabbro 



Quartz diorite 



Granodiorite 



Granite (calc-alkalic) 



Granite (alkalic) 



Granite pegmatite 



Nepheline syenite 



50-70 

 40-60 

 35-55 

 30-45 

 20-30 

 3-20 

 60-150 



Levinson and Borup, 1960; Vainshtein and others, 

 1959). 



TYPES OF DEPOSITS 



PRIMARY DEPOSITS 



Despite the fact that zircon tends to be enriched in 

 late-stage magmatic differentiates and is a common 

 accessory mineral in many rock types, primary de- 

 posits having economic value are rare. An example 

 is the uranif erous zirconium deposits in the P050S de 

 Caldas Plateau, Brazil, which contain baddeleyite 

 and zircon in commercial quantities and yielded an 

 estimated 100,000 metric tons of zirconium ore con- 

 centrate before 1953 (Tolbert, 1966). These deposits 

 consist of veins and disseminations of baddeleyite 

 and zircon in nepheline syenite and phonolite of an 

 alkaline intrusive that was emplaced in gneiss and 

 granite in the southwestern part of the Brazilian 

 shield. The veins are believed to be of hydrothermal 

 origin (Tolbert, 1966), but the primary ores may 

 have resulted from lateritic concentration as de- 

 scribed by Wedow (1967) for thorium and rare- 

 earth deposits nearby. Concentrations of baddeleyite 

 and zircon were in primary veins disseminated in 

 decomposed bedrock in eluvial deposits on hill slopes, 

 and in alluvial placer deposits along streams and in 

 terraces. Most of the ore production was from 

 placers of alluvial and eluvial origin. Only a small 

 amount was produced from shallow workings along 

 veins. Resources of zirconium ore in the region were 

 estimated to be 50,000-70,000 metric tons which con- 

 tained 60-85 percent ZrOa and about 0.5 percent 

 uranium (Tolbert, 1966). 



Other primary deposits are pegmatites which con- 

 tain rare zirconium minerals or gem-quality zircon, 

 such as those in the Zirconia district, Henderson 

 County, N. C. (Pratt, 1916). Deposits of this type 

 are of little economic significance at present. 



SECONDARY DEPOSITS 



In the sedimentary cycle, zircon, being heavy 

 (sp gr 4.7) and resistant to chemical decomposition 

 and erosion, is concentrated with .other heavy re- 



sistate minerals, such as rutile, ilmenite, monazite, 

 and garnet, in placer deposits in stream terraces, 

 along beaches, and in sand dunes. Deposits of this 

 type are the commercial sources of zircon, generally 

 as a coproduct or byproduct of titanium minerals or 

 combinations of other heavy minerals. Examples of 

 commercial zircon-bearing titaniferous sand deposits 

 are Trail Ridge, Fla., and deposits along beaches 

 near the Queensland-New South Wales border, 

 Australia, and along beaches in Western Australia. 

 About 1 ton of zircon is produced for each ton of 

 rutile in concentrates from the Australian deposits 

 (Stamper and Chin, 1970b). 



Zircon is also found in small percentages in some 

 phosphatic sediments and in some sand and gravel 

 deposits. Potentially recoverable zircon is usually 

 discarded in waste products from phosphate mining 

 and sand and gravel production. In 1967, for ex- 

 ample, 44,000 tons of zircon was discarded along 

 with 60,000 tons of ilmenite and 5,000 tons of mo- 

 nazite as waste products in Florida phosphate opera- 

 tions (Stow, 1968). 



Zircon deposits in lithified titanium-rich placers in 

 sandstones or in metamorphosed sandstones are po- 

 tentially of economic importance. Sandstones of the 

 Precambrian Ocoee Supergroup contain beds having 

 4.5-9.0 percent zircon (Wedow and Hobbs, 1968) . 



RESOURCES 



IDENTIFIED RESOURCES 



The identified resources of zircon are principally 

 in titanium-rich and phosphate-rich sands in placer 

 deposits and in fossil placers in titaniferous sand- 

 stone. Resources of baddeleyite in South Africa and 

 Brazil, however, include primary and residual de- 

 posits. Data on world resources of zircon are incom- 

 plete. Identified zircon resources, in short tons of 

 zircon equivalent, are given in table 161. These 

 resources contain approximately 17 million tons of 

 zirconium and 0.3 million tons of hafnium. 



The United States has the world's greatest identi- 

 fied resources of zircon (Stamper and Chin, 1970b). 

 More than 70 percent of the domestic resources are 

 in the Atlantic Coastal States of Florida, Georgia, 

 South Carolina, and New Jersey. The distribution of 

 zircon resources in the United States is shown in 

 table 162. The amount for Florida is modified from 

 published resource data to compensate for estimated 

 production. 



The identified resources of zircon in the United 

 States, estimated at 10.8 million tons, contain ap- 

 proximately 5 million tons of zirconium and 0.1 mil- 

 lion tons of hafnium. A portion of the resources in 



