UNITED STATES MINERAL RESOURCES 



MOLYBDENUM 



By R. U. King, D. R. Shawe, and E. M. MacKevett, Jr. 



CONTENTS 



Page 



Abstract of conclusions 425 



Introduction 425 



Exploitation 426 



Geolo^c environment 427 



Geochemistry 427 



Mineralogy 427 



Types of deposits 427 



Porphyry deposits 427 



Climax, Colorado 428 



Urad-Henderson, Colorado 429 



Questa, New Mexico 429 



Contact-metamorphic deposits 429 



Quartz veins 429 



Pegmatites 429 



Bedded deposits in sedimentary rocks 430 



Resources . 430 



Identified and hypothetical resources 430 



Speculative resources 431 



Prospecting 433 



Problems for research 434 



Selected bibliography 434 



FIGURE 



52. 



Map showing location of molybdenum resources 

 in and near Colorado and northern New 

 Mexico in relation to various geologic para- 

 meters 432 



TABLE 



85. Estimated magnitude of world resources of 

 molybdenum 



431 



ABSTRACT OF CONCLUSIONS 



Molybdenum, a rare metal widely dispersed in the rocks 

 of the earth's crust, occupies an essential place in today's 

 highly sophisticated industries. 



World production of molybdenum is about 200 million 

 iwunds per year, of which about 60 percent is produced in 

 the United States. Identified resources amounting to about 

 17.5 million tons of molybdenum in the United States and 

 about 32 million tons in the world and occurring both as the 

 primary metal sulfide in large low-grade porphyry molybde- 

 num deposits and as a subsidiary metal sulfide in large low- 

 grade porphyry copper deposits, seem adequate to supply 

 world needs for the forseeable future. 



To assure economic availability of these resources and to 

 discover additional resources that surely will be needed if 

 world demand continues to escalate and if environmental 

 problems should tend to restrict the commercial development 

 of resources, employment of our most sophisticated explora- 

 tion techniques will be essential. Successful prediction of the 

 location of undiscovered molybdenum resources will depend 

 upon an understanding of the genetic relationship of molyd- 

 denum to associated magmatic rocks, the environments in 

 which these magmatic rocks were emplaced, and the role of 

 plate tectonics in developing favorable environments and 

 mechanisms for the generation and emplacement of molyb- 

 denum-carrying rocks. 



INTRODUCTION 



Molybdenum, discovered in the last 1770's, is a 

 metal of fairly recent entry into the commercial 

 market, having come into signilicant use during the 

 1920's as a result of extensive metallurgical research 

 into its alloying properties and as a result of the 

 establishment at Climax, Colo., of proved reserves 

 sufficient to supply world demand for many years 

 at a reasonable price. Its importance as an alloying 

 metal is due chiefly to the increase in hardness, 

 toughness, and resistance to corrosion and wear at 

 elevated temperatures that it imparts to iron, steel, 

 and stainless steel. 



Molybdenum is a silvery-gray metal having a 

 high specific gravity (10.2) — slightly higher than 

 copper — and a melting point of 2,620°C — the fifth 

 highest melting point of all metals. It is ductile and 

 has a hardness of about 200 V.P.N. (Vickers Pyra- 

 mid Number) and its coefficient of thermal expan- 

 sion is among the lowest of metals. It is resistant 



U.S. GEOL. SURVEY PROF. PAPER 820 



425 



