UNITED STATES MINERAL RESOURCES 



THALLIUM 



By Keith Robinson 



CONTENTS 



Abstract of conclusions 631 



Introduction 631 



Exploitation 632 



Geologic environment 633 



Geochemistry 633 



Distribution in minerals and rocks 634 



Resources 634 



Problems for research 635 



References cited 636 



TABLE 



131. World reserves and potential resources of 



thallium 635 



ABSTRACT OF CONCLUSIONS 



Thallium, a soft, heavy, readily oxidizable metal, is re- 

 covered as a byproduct from the flue dust and residue pro- 

 duced in the smelting of base metals, principally zinc. A 

 75-percent recovery factor has been calculated. 



The current uses for thallium are limited, being primarily 

 confined to electronics and metallurgical processing; lesser 

 applications are in glass, explosives, agriculture, and 

 medicine. 



U.S. and total world identified resources of thallium from 

 zinc, lead, and iron sulfides are estimated at 266 and 1,390 

 tons respectively. Additional U.S. and total world resources 

 contained in coal ash are 119,000 and 715,000 tons. Identified 

 manganese nodules occurring on the sea floors are estimated 

 to contain 9.9 million tons of thallium. Assuming no unfore- 

 seen demand, the world supply of thallium from identified 

 zinc sulfide sources will be exhausted in 43 years at the 

 present rate of consumption, and from all identified sulfide 

 sources in 70 years. 



Evidence suggests that the variable abundance of thallium 

 in specific minerals may, in part, be controlled by tempera- 

 ture and pressure. This could prove valuable in delineating 

 the mineralized potential of areas for other conmiodities. 



INTRODUCTION 



Thallium was recognized and named as a new 

 element by Sir William Crooks in 1861 while making 

 a spectroscopic search for tellurium in seleniferous 

 deposits from a sulfuric acid plant in the Hartz 

 Mountains of Germany. He named the newly dis- 

 covered element "thallium," from the Latin word 

 thallus, meaning budding twig, because its bright- 

 green spectral line was the color of young vegeta- 

 tion. 



Thallium metal is extracted and refined as a by- 

 product from the flue dust and residue produced in 

 the smelting of base-metal ores. Zinc ore is the pri- 

 mary source of thallium metal. It is estimated that 

 approximately 75 percent of the thallium is recov- 

 ered from the processed flue dust and residue. In 

 addition, thallium is recovered from the smelting of 

 other base metals such as lead, and may also be 

 recovered from the trace amounts occurring in 

 pyrite, during the roasting of pyrite to produce 

 sulfuric acid. 



The most important, nontoxic, uses of thallium 

 are in the electronic and metallurgical processing 

 industries ; lesser uses are in glass, explosives, agri- 

 culture, and medicine. 



Pure thallium has poor mechanical properties, but 

 when introduced into other metals in small quanti- 

 ties it can significantly improve their mechanical 

 and electrical properties. Thallium improves the 

 hardness of lead, and its alloy with lead is corrosion 

 resistant ; its alloy with copper is heat resistant and 

 of high electrical and thermal conductivity; and its 

 alloy with aluminum and zinc improves the abrasion 

 resistance of bearings, particularly in the absence 

 of petroleum lubricants — a property which may 

 have considerable application in the aerospace pro- 

 gram. The presence of thallium as micro-occlusions 

 improves the machinability of stainless steel. It is 

 used with indium, mercury, and gold in solders for 

 ceramics and semiconductors. The quality of furnace 



U.S. GEOL. SURVEY PROF. PAPER 820 



631 



