UNITED STATES MINERAL RESOURCES 



NIOBIUM (GOLUMBIUM) AND TANTALUM 



By Raymond L. Parker and John W. Adams 



CONTENTS 



Page 



Abstract of conclusions 443 



Introduction 443 



Exploitation 444 



Environmental problems 445 



Geologic environment 445 



Geochemistry 445 



Minerals 446 



Types of deposits 446 



Alkalic rock complexes 446 



Nepheline syenites 446 



Carbonatites 447 



Granitic rocks 448 



Pegmatites 448 



Placer deposits 449 



Resources 450 



Identified resources 450 



Undiscovered resources 452 



Prospecting techniques 452 



Problems for research 453 



References 453 



FIGURE 



53. Graph showing world production and U.S. im- 

 ports of niobium-tantalum concentrates, 1937- 

 71 



TABLES 



90. 

 91. 

 92. 



Reserves of niobium and tantalum 



Conditional resources of niobium and tantalum. 



Unevaluated resources of niobium and tantalum 



Summary of identified resources of niobium 



and tantalum in the world 



444 



Page 

 450 

 451 

 451 



452 



ABSTRACT OF CONCLUSIONS 

 Niobium (columbium) and tantalum have become im- 

 portant metals in modern technology because of their metal- 

 lurgical, electronic, chemical, and nuclear uses. Both metals 

 occur in nature almost entirely as single isotopes Nb"^ and 



Ta^°^ and are present in the earth's crust in estimated abund- 

 ance of 20 ppm (parts per million) and 2 ppm respectively. 

 Niobium and tantalum have strong geochemical coherence 

 and occur together in most rocks and minerals; however, 

 some rock types such as nepheline syenite and carbonatites 

 contain niobium in great preponderance over tantalum. These 

 elements occur in minerals chiefly as oxides and multiple 

 oxides, hydroxides, a few silicates, and one borate; more 

 than 90 mineral species are known. 



Ore concentrations of niobium and tantalum occur in 

 carbonatites and other rocks of alkalic complexes, certain 

 types of granite, pegmatites, placers, and residual deposits. 

 Most of the known deposits of niobium are found in car- 

 bonatites and those of tantalum are contained in pegma^ 

 tites and placers. Most of the world's resources of niobium 

 and tantalum lie outside the United States, and consequent- 

 ly these metals are almost entirely imported. Known re- 

 sources within the United States could be utilized during 

 times of national emergency but cannot at present compete 

 with the larger and higher grade foreign deposits. On a 

 worldwide basis, resources of niobium are more than ade- 

 quate to supply the projected needs to the year 2000, but 

 resources of tantalum barely meet these projected needs. 

 Geologic research is needed to explore the possibilities of the 

 existence of new types of tantalum deposits. 



INTRODUCTION 



Niobium (columbium) ^ and tantalum are two 

 similar metals that have become increasingly im- 

 portant in modern technology because of physical 

 properties that are useful in certain metallurgical, 

 electronic, chemical, and nuclear applications. These 

 metals were discovered in 1801-02, but for more 

 than a century and a quarter no practical use was 

 found for them. Commercial usage of niobium began 

 about 1930 when it was first used as an alloying 

 element in steel. Tantalum, although used to a minor 

 degree in the chemical and electrical industries in 

 the 1920's, was not extensively used until 1940 when 

 it became an important material for capacitors. Both 

 metals have been in strategically short supply at 

 various times during and since World War II. 



'Niobium (Nb) is the preferred name in chemistry and most other 

 sciences and was officially adopted by the International Union of Pure 

 and Applied Chemistry in 1960. The name columbium is still used to 

 some extent in metallurgy and mineral trades. 



U.S. GEOL. SURVEY PROF. PAPER 820 



443 



