UNITED STATES MINERAL RESOURCES 



TUNGSTEN 



By S. Warren Hobbs and James E. Elliott 



CONTENTS 



Page 



Abstract of conclusions 667 



Introduction 667 



Exploitation 668 



Geologic environment 668 



Geochemistry 668 



Mineralogy 670 



Types of deposits 671 



Contact-metamorphlc deposits 671 



Tungsten-bearing vein deposits 672 



Stockwork and related deposits 673 



Other modes of occurrence 674 



Resources 675 



Identified and hypothetical resources 675 



Speculative resources 675 



Prospecting techniques 676 



Problems for research 677 



References cited 678 



General references 678 



FIGURE 



73. Graph showing U.S. production and price of 

 tungsten, 1900-1971 



TABLES 



145. Minerals of tungsten 



146. Geology and reserves of principal tungsten de- 



posits of the world 



671 



ABSTRACT OF CONCLUSIONS 



Most of the major tungsten deposits of the world have a 

 close spatial and genetic association with granitic intrusive 

 rocks or their related porphyries. Although several very 

 diverse modes of occurrence are recognized, more than 95 

 percent of all tungsten production has come from three types 

 of deposits: contact-metamorphic deposits (tactites), quartz 



veins, and stockworks. A close genetic association between 

 igneous rock and ore is strongly suggested by the localiza- 

 tion of many ore bodies of these kinds within or adjacent 

 to the roof zones of major Intrusive bodies, or close to 

 cupolas, stocks, and bosses. 



U.S. tungsten reserves in known deposits or their geologi- 

 cally reasonable extensions are estimated at 15 million short 

 ton units (1 short ton unit=20 pounds WO3). This is about 

 6.8 percent of known world reserves, of which approximately 

 60 percent are In China. Subeconomic resources in identified 

 or geologically plausible deposits in the United States are 

 conservatively estimated to contain two to three times the 

 reserves. Covered areas in the United States probably con- 

 tain concealed deposits that are comparable in grade and 

 total tonnage to those now known. 



The United States has the potential for adequate tungsten 

 production into the foreseeable future, provided it is willing 

 to pay the price of essential research, extensive exploration, 

 and the processing of high-cost low-grade ores. 



INTRODUCTION 



Tungsten in its pure form is a silver-gray or tin- 

 white metal of high specific gravity (19.35) whose 

 usefulness is related directly to its special or unique 

 physical and mechanical properties: the metal has, 

 next to carbon, the highest melting point of all the 

 elements (3,400°C) ; its tensile strength (maximum 

 of 590,000 lbs per sq in.) is the highest of all metals; 

 and its high heat of sublimation, low compressibility, 

 and low coefficient of thermal expansion are further 

 attributes of importance in certain applications. 

 These fundamental properties are due to the nature 

 of the crystalline lattice of tungsten atoms. Tungsten 

 is one of the so-called transition metals which are 

 characterized by incompleted "d" levels in the elec 

 tronic configuration surrounding the nucleus. It ap- 

 parently has the optimum number of vacancies in 

 the fifth "d" level to establish an exceptionally 

 strong interatomic bonding that explains, at least 

 qualitatively, the metal's exceptional properties. 



The major uses of tungsten relate not only to the 

 special characteristics of the metal itself but also to 

 the properties that it imparts to its compounds and 



U.S. GEOL. SURVEY PROF. PAPER 820 



667 



