UNITED STATES MINERAL RESOURCES 



SCANDIUM 



By John W. Adams 



CONTENTS 



Abstract of conclusions 567 



Introduction 567 



Geologic environment 567 



Geochemistry 567 



Mineralogy 568 



Types of deposits 568 



Pegmatites 568 



Greisen and vein deposits 569 



Variscite deposits 569 



Enrichments in other materials 569 



Resources 569 



Problems for research 570 



References cited 570 



ABSTRACT OF CONCLUSIONS 



Scandium is a rare metal that at present has only minor 

 industrial applications. Geochemically, it is a highly dis- 

 persed element that occurs chiefly in trace amounts in the 

 ferromagnesian minerals of igneous rocks. Scandium may 

 be concentrated in pegmatites, some of vi^hich have been 

 mined for thortveitite, one of the fevif independent scandium 

 minerals. It may also be present in anomalously high amounts 

 in some phosphate deposits and tungsten ores. Some scan- 

 dium has been produced from domestic and foreign uranium 

 ores in mills where it accumulated in residues that developed 

 during the extraction of uranium. Scandium apparently is 

 not being recovered from any source at the present time, but 

 if demand were to increase, the element could be obtained 

 again as a byproduct of uranium-ore processing as well as 

 from certain tungsten ores and phosphatic rocks. 



INTRODUCTION 



Scandium (Sc) is a soft silvery metal that was 

 discovered in 1879 but was not prepared in its 

 metallic form until 1937. It has atomic number 21 

 and is trivalent. It is sometimes included as a mem- 

 ber of the rare-earth group but differs markedly 

 from the rare earths in its geochemical behavior. 



Scandium is a commodity whose statistics of pro- 

 duction and demand are quoted in grams rather than 

 tons. Until a few years ago, its sole and very lim- 



ited commercial use was as a tracer of fluid flow in 

 oil wells. This purpose requires the irradiation of 

 natural Sc*=^ in a nuclear reactor to produce the 

 radioactive isotope Sc'% which has a half life of 

 84 days. Recently, however, a new application for 

 scandium has been found in high-intensity lamps — 

 the metal produces light in a more balanced color 

 range. Several thousand grams of scandium are now 

 used in these lamps annually (U.S. Bur. Mines, 

 1971). 



Scandium is an expensive metal owing to both 

 the cost of extraction and the very limited demand. 

 In the past, it has been obtained almost exclusively 

 from the rare mineral thortveitite, a scandium- 

 yttrium silicate mined in Norway and Madagascar, 

 but since 1960 its chief source has been waste prod- 

 ucts from certain uranium mills that use an or- 

 ganophosphate solvent extraction process for ura- 

 nium recovery (Ross and Rosenbaum, 1962). 

 Scandium has not been produced from uranium 

 mills in the United States for several years, and 

 the limited demand has been met from producers' 

 stockpiles or from imports from Canada and Au- 

 stralia (U.S. Bur. Mines, 1971). 



Should the need for scandium increase drastically, 

 it could be produced from several possible sources, 

 but its price would probably always be high if low- 

 grade raw materials had to be used. 



GEOLOGIC ENVIRONMENT 



GEOCHEMISTRY 



Scandium tends to be dispersed like the rare- 

 earth elements, but it is dispersed to an even greater 

 degree. Its crustal abundance has been variously 

 estimated to be 5-30 ppm (parts per million) 

 (Fryklund and Fleischer, 1963; Parker, 1967), 

 about that of some lanthanide elements, but much 

 greater than that of such familiar elements as anti- 

 mony, mercury, molybdenum, and silver, which are 

 more readily available owing to their tendency to 



U.S. GEOL. SURVEY PROF. PAPER 820 



567 



