Geochemistry of 

Niobium and Tantalum

GEOLOGICAL SURVEY PROFESSIONAL PAPER 612

Geochemistry of 

Niobium and Tantalum

By RAYMOND L. PARKER and MICHAEL FLEISCHER

GEOLOGICAL SURVEY PROFESSIONAL PAPER 612

A review of the geochemistry of niobium 

and tantalum and a glossary of 

niobium and tantalum minerals

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. GS 68-344

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 50 cents (paper cover)
CONTENTS

Abstract_ _ __-_.. _____________________

Introduction. _________________________

General geochemical considerations. _____

Abundance of niobium and tantalum_____

Crustal abundance-________________

Limitations of data________________

Abundance in rocks._______________

Qualifying statement.__________

Igneous rocks_________________

Sedimentary rocks.____________

Abundance in meteorites and tektites. 

Isomorphous substitution.______________

Geochemical behavior._________________

Magma tic rocks ___________________

Granitic rocks_________________

Albitized and greisenized granitic rocks. 

Granite pegmatites._________________

Nepheline syenite..__________________

Alkalic ultramafic rocks ______________

Page

1

2

2

3

3

3

5

5

6

10

12

13

15

15

16

19

19

21

22

Page

Geochemical behavior Continued 

Magmatic rocks Continued

Volcanic rock series______--____---__.__-_-__ 2.

Sedimentary rocks______________________________ 2.

Deposits of niobium and tantalum.___________________ 2£

Suggestions for future work__--___-_------__-___---_- 26

References, exclusive of glossary______________________ 27

Glossary of niobium and tantalum minerals.___________ 3C

Part I Classification of minerals of niobium and

tantalum according to chemical types_________ 31

Part II Niobium and tantalum minerals..-_______ 32

Part III Minerals reported to contain 1-5 percent

niobium and tantalum_______________________ 38

Part IV Minerals in which niobium and tantalum 

have been detected in quantities less than 1 

percent._____________________________________ 38

References for glossary of niobium and tantalum 

minerals _________________________________________ 38

Index of mineral names in glossary__________________ 41

TABLES

Page

TABLE 1. Niobium and tantalum contents in the earth's crust according to different authors_________----_-----__--_----_ ?

2. Analytical determinations of niobium and tantalum in standard granite G-l and standard diabase W-l __ 4-

3. Average niobium and tantalum contents in different types of rocks, as given by previous authors_____-_------_ f

4. Niobium and tantalum contents of some granites, quartz monzonites, and granodiorites, and volcanic rocks of

similar chemical composition________________________________________________-__--.---------------- 7

5. Abundance of niobium and tantalum in different magmatic rocks_______----------------------------------- ^

6. Niobium and tantalum contents of some sodic and alkalic granites and rhyolites of similar chemical composition. _ _ _ ?

7. Niobium and tantalum contents of some nepheline syenites, phonoljtes, and other nepheline-bearing felsic rocks. _ £

8. Niobium and tantalum contents of nepheline syenites and phonolites from different massiis_____-__-_-___---- 1C

9. Niobium and tantalum contents of some syenites and trachytes--.-.-------------------------------------- 1C

10. Niobium and tantalum contents of some feldspathoidal rocks.-------------------------------------------- 11

11. Niobium and tantalum contents of some gabbroic, basaltic, and alkalic basaltic rocks._______________________ 11

12. Niobium and tantalum contents of some ultramafic rocks___--__-_--------_------------------------------ 12"

13. Niobium and tantalum in some sedimentary rocks and other rocks or deposits.__________________-__-_------- 12

14. Niobium and tantalum contents of meteorites and tektites-__-__________-------_------------------------- 13

15. Physical constants of some elements_-_----__-_____--_____--__-____-_---------------------------------- 12

16. Schemes of isomorphous substitution in niobium-tantalum-bearing minerals.____________^_---------------- If

17. Distribution of niobium and tantalum in granitic rocks of the Kalbinsk massif, U.S.S.R.____-,---___-_------ 17

18. Distribution of niobium and tantalum in granitic rocks from the eastern Sayan Mountains, U.S.S.R_________-__ 17

19. Tantalum in hornblende and biotite from igneous rocks of the southern California batholith______________---- IS

20. Comparison of percentage of occurrence of niobium minerals in pegmatites with averages of niobium in accompanying muscovites _________________________________________-__-_-___-------------------------- 2C

21. Niobium and tantalum contents in micas from pegmatites of different ages and from the enclosing rocks in the

northwestern White Sea region, U.S.S.R_____._._________.______________________-------------------- 21

22. Average contents of niobium and tantalum in some massifs of nepheline syenite, U.S.S.R____--_---_---------- 21

23. Average contents of Nb2O5 and Ta 2O5 and their ratios in some minerals of alkalic-ultramafic rocks of the Kola

Peninsula, TJ.S.S.R_______________________________________________._______._ 2?

24. Ratios of Nb2O5 : Ta2O5 in minerals grouped according to their paragenetic association, Kola Peninsula, U.S.S.R__ 24

25. Classification of deposits of niobium and tantalum________________________-_-_____-___------------------ 26

in

GEOCHEMISTRY OF NIOBIUM AND TANTALUM

By RAYMOND L. PARKER and MICHAEL FLEISCHER

ABSTRACT

This report on the geochemistry of niobium and tantalum is 

chiefly a summary of works published since those of Rankama, 

and it is not a product of original research. It summarizes what 

is known of the geochemical characteristics of these elements and 

their occurrence in various types of minerals, rocks, and ores. A 

glossary of niobium and tantalum minerals and an extensive 

list of references on the geochemistry and mineralogy of these 

elements are included.

Niobium (atomic number 41) and tantalum (atomic number 

73) occur in nature almost entirely as single isotopes (Nb93 and 

Ta181), and they commonly substitute for one another in minerals 

because they both have similar ionic radii and occur mostly in 

the quinquevalent state. A great preponderance of one element 

over the other rarely occurs in certain types of rocks such as 

nepheline syenites (niobium-rich) or lithium-bearing pegmatites 

(tantalum-rich). Both elements are lithophilic and are enriched 

in the silicate crust of the earth.

Most niobium and tantalum minerals are oxides, although 

some rare silicates and one borate are known. Many oxide, 

phosphate, tungstate, and silicate minerals of other elements 

contain minor amounts of niobium and tantalum in isomorphous 

substitution for such elements as titanium, tungsten, tin, zirconium, and hafnium. Minerals containing niobium and tantalum 

are listed in the glossary.

The abundance of niobium and tantalum in the earth's crust 

according to modern estimates is near 20 and 2 ppm respectively, 

but abundance of these elements in different types of rocks 

comprising the crust is highly variable. Crustal abundance as 

well as abundance in various rock types are subject to considerable 

uncertainty in accuracy and validity because of limitations 

imposed by availability of analytical data, by accuracy of 

analytical procedures, and by adequacy of sampling. Additional 

limiting factors are improper classification of rocks and geographic bias. A compilation of abundance tables for different 

rocks shows that niobium is most abundant in alkalic rocks such 

as nepheline syenite, syenite, alkalic mafic and ultramafic rocks, 

and sodic and alkalic granite. Tantalum generally accompanies 

niobium with an abundance of one-tenth to one-fifteenth that 

of niobium although it is extremely low in some niobium-rich 

alkalic complexes. (See tables.)

In sedimentary rocks the highest niobium contents are found 

in deep sea manganese nodules and sediments and in bauxites; 

the highest tantalum contents are found in marine clays and 

bauxite, whereas a paucity of tantalum exists in the deep sea 

environment. Some physically and chemically resistant minerals 

of niobium and tantalum accumulate locally in placers and are 

found as rich accumulations preserved in some sandstones and 

conglomerates.

Niobium and tantalum in meteorites are a fraction of their 

clarke values, although in tektites the tantalum content is close 

to that for the earth's crust.

Most univalent, divalent, and some of the larger trivalent 

ions of trace elements exist free in magma and their crystallization can be interpreted satisfactorily in terms of ionic radius, 

ionic charge, and electronegativity or ionic potential according 

to the rules of Goldschmidt and of Ringwood. Ions with charges 

greater than three and some of the smaller trivalent ions, however, form complexes with oxygen, hydroxyl, fluorine, chlorine, 

and other anions, and these complexes maintain their identity 

during the crystallization process. The higher the ionic potential of the element the more stable is the complex formed. 

Niobium and tantalum have ionic potentials of intermediate 

values (Nb+5 7.25, Ta+5=7.35), sufficiently high to form normally stable complexes, although they are also in the range 

where partial dissociation under certain conditions is possible. 

Niobium and tantalum probably form tetrahedral complexes, 

NbO4-3 and TaOr3, and octahedral complexes, NbO6~7 and 

TaO6~7. The octahedral form is the one found in most niobiumbearing minerals. Neither tetrahedral nor octahedral complexes 

of niobium and tantalum can be easily incorporated into most 

silicate minerals according to the rules of Ringwood; hence these 

elements tend to accumulate as complexes in the magma during 

crystallization until sufficiently concentrated to allow precipitation, most likely as multiple oxide minerals, or are scavenged 

during crystallization by accessory minerals of titanium or 

titanium and iron.

These complex-forming elements can be considered as individual ions for the purpose of examining schemes of isomorphism and the electrostatic balances involved. Two types of 

isomorphism are prevalent, isovalent and heterovalent. The 

common substitution of niobium for tantalum is the isovalent 

type. The substitution of titanium for niobium and tantalum 

is the heterovalent type.

The geochemical behavior of niobium and tantalum in granitic rocks depends to a certain extent on the paragenesis of 

the titanium minerals. Monazite-bearing granites containing 

ilmenite and rutile commonly contain niobium and tantalum 

in accessory biotite, whereas allanite-bearing granites containing 

sphene and magnetite commonly have niobium and tantalum 

concentrated in sphene with only subordinate amounts in the 

biotite. In some granitic rocks the niobium and tantalum are 

concentrated in hornblende. Most likely these elements substitute for titanium in the minerals concerned. Some rare granites contain niobium and tantalum in discrete accessory minerals of these elements. Although exceptions occur, niobium and 

tantalum generally accumulate in the later differentiates during 

crystallization of granites, and there is a tendency for tantalum 

to be concentrated relative to niobium in certain albitized or
GEOCHEMISTRY OF NIOBIUM AND TANTALUM

greisenized rocks. The separation of niobium from tantalum and 

the concentration of tantalum are attributed to changes in 

alkalinity-acidity of the crystallizing medium and to the complexing of these elements with fluorine, tantalum-fluorine complexes being more mobile and stable than niobium-fluorine 

complexes.

High concentrations of niobium and tantalum occur in granitic 

pegmatites both as discrete niobium-tantalum minerals and as 

minor constituents in the lattices of mica, garnet, tourmaline, 

ilmenite, zircon, and other minerals. Complexly zoned pegmatites commonly are more intensely mineralized with niobium 

and tantalum than other types. Those pegmatites having a 

strong development of albite and lithium- and fluorine-bearing 

minerals commonly are enriched in tantalum. Tantalum generally 

tends to be concentrated with respect to niobium in successive 

later phases of many granitic pegmatites.

Nepheline syenite is well known for its high concentration of 

niobium. Some Russian nepheline syenite complexes have 

concentrations of tantalum (Nb:Ta = about 12:1) also, but 

many alkalic complexes elsewhere are notably poor in tantalum. 

In miaskitic nepheline syenites (K2O + Na2O:Al2O3 = <1) 

niobium and tantalum are concentrated in titanium and zirconium minerals and also form independent minerals of niobium 

and tantalum in late magmatic and postmagmatic derivatives. 

In agpaitic nepheline syenites (K2O 4- Na2O: Al2Os = 1 or more) 

most niobium and tantalum are fixed in titanium and zirconium 

minerals even though the average contents of niobium and 

tantalum in these rocks is greater than in miaskitic syenites.

Alkalic ultramafic complexes, typified by those of the Kola 

Peninsula, TJ.S.S.R-, characteristically contain multiple phases 

in concentric arrangement. The phases consist of varieties of 

olivinite, pyroxenite including melilite-, perovskite-titanomagnetite-, and nepheline-bearing types, melteigite-ijoliteurtite, and others. In the products of magmatic crystallization 

niobium and tantalum enter into the titanium-bearing ironmagnesium-silicate and oxide minerals. In products of residual 

crystallization, such as alkalic pegmatites, niobium and tantalum 

are concentrated in titanium and zirconium minerals and in 

independent niobium minerals. In postmagmatic rocks, such 

as carbonatites, niobium and tantalum are concentrated in 

independent minerals such as pyrochlore, lueshite, dysanalyte, 

and others, apparently in part remobilized and reconcentrated 

in the process of postmagmatic alteration of pyroxenes and 

other minerals. In general, niobium is progressively enriched in 

successive phases, and tantalum is depleted relative to niobium.

Niobium and tantalum dissolved during the weathering cycle 

tend to be concentrated in hydrolyzates; however, an appreciable 

amount of niobium escapes to the ocean where it precipitates 

with clays and manganese oxide producing a degree of relative 

enrichment of niobium over tantalum in this environment. A 

similar fractionation of niobium and tantalum occurs in clays 

grading from arid source areas to a basin of marine deposition, 

as is shown by progressive decreases in the Nb:Ta ratio. Differences in solubility of organic niobium and tantalum compounds formed by weathering and differences in behavior of 

these elements in solution with titanium, zirconium, and others 

are possible causative factors. Hydrolyzate minerals derived 

from rocks originally rich in niobium and tantalum tend to be 

rich in these elements also.

Commercial recovery of niobium is mostly from columbitetantalite, pyrochlore, and euxenite ores and possibly from rocks 

containing loparite and murmanite. The recovery of tantalum 

is chiefly from columbite-tantalite, microlite, or euxenite ores.

Future advances in the field of niobium-tantalum geochemistry 

will depend on the availability of a large number of additional,

accurate analyses of rocks and minerals from well-studied 

complexes.

INTRODUCTION

The most comprehensive researches in the field of 

geochemistry of niobium and tantalum were made by 

Kalervo Kankama (1944, 1948), and most of the 

geochemical characteristics of these elements were 

outlined in these works. In the last 10 year^ the work 

on the geochemistry of these elements has been dominated largely by Russian scientists working principally in the Institute of Mineralogy, Geochemistry, 

and Crystal Chemistry of Rare Elements and the 

V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, both in Moscow. Despite the large 

volume of literature on the subject since Rankama's 

work, concepts in the field have not changed greatly, 

although many principles have been verified or modified slightly as a result of the accumulation of greater 

amounts of data and more accurate data. The chief 

deterrent in the advancement of knowledge has been 

the lack of analytical data in the very low levels of 

concentration of these elements as found in ordinary 

rocks.

This report is chiefly a summary of works published 

since those of Rankama and is not a product of original research. Comprehensive works of M. V. Kuz'- 

menko (1961, 1964) and E. M. Es'kova (1964) have 

furnished considerable substance to this summary. 

Our purpose has been to review the mode of occurrence 

of niobium and tantalum and point out characteristics of geochemical behavior under certain geological conditions. No attempt has been made to discuss 

specific ore deposits or to delve deeply into that subject, but rather to summarize what is known of the 

geochemical characteristics of these elements and their 

occurrence in various types of minerals, rocks, and 

ores. A glossary of niobium and tantalum minerals is 

included, and an extensive list of references on the 

geochemistry and mineralogy of these elements is 

given.

It is hoped that this review will serve to point out 

weaknesses in the knowledge of niobium and tantalum 

geochemistry and the areas where further geochemicai 

research is needed.

We wish to express our gratitude to David Gottfried 

for discussing niobium and tantalum geochemistry 

many times with us and for making available unpublished data.

GENERAL GEOCHEMICAL CONSIDERATIONS

Niobium is a chemical element of atomic number 

41 and atomic weight 92.91; tantalum has atomic 

number 73 and atomic weight 180.95. In nature both 

elements consist almost entirely of single isotopes
GENERAL GEOCHEMICAL CONSIDERATIONS

(Strominger and others, 1958). Niobium has one 

isotope, Nb93 . Tantalum has two isotopes, Ta181 and 

Ta180, although Ta180 accounts for only about 0.01 

percent of the element (Evans and others, 1955; White 

and others, 1955).

Niobium and tantalum are a pair of elements with 

strong geochemical coherence; that is, they are closely 

associated and are found together in most rocks and 

minerals in which they occur. Great preponderance of 

one element over the other more rarely occurs in certain 

types of rocks such as some nepheline syenites (niobium-rich) and lithium-bearing pegmatites (tantalumrich) or in some rocks modified by metasomatic processes.

The principal reasons for such coherence are the 

similar ionic radii and the identical valence states of 

the two elements, Nb+5 = 0.69 A and Ta+5 = 0.68 A, 

which apparently are fundamental parameters controlling entry of the elements into crystal structures. 

These elements are found in the quinquevalent state 

in most naturally occurring compounds. The slightly 

smaller ionic radius of Ta+5 than that of the much 

lighter Nb+5 is a result of the lanthanide contraction. 

(See Kankama and Sahama, 1950, p. 107-112.)

Both niobium and tantalum are lithophilic elements, 

showing a strong affinity for oxygen and are enriched 

in the silicate crust of the earth (Rankama and Sahama, 

1950, p. 88). Most niobium-tantalum minerals are 

oxides, although some rare silicates and one borate of 

these elements are known. Niobium and tantalum 

occur also in minor amounts in many oxide, tungstate, 

phosphate, and silicate minerals of other elements. In 

these minerals, niobium and tantalum are closely 

associated with titanium, tungsten, tin, zirconium, and 

hafnium for which they commonly substitute isomorphously by virtue of the similarity of their ionic radii 

and other physical properties. Commonly occurring in 

the same minerals with niobium and tantalum or in 

coexisting minerals in the same rocks are uranium, 

thorium, rare earths, iron, manganese, bismuth, and 

many other elements.

ABUNDANCE OF NIOBIUM AND TANTALUM 

CBUSTAL ABUNDANCE

Early estimates of the crustal abundance of niobium and tantalum, which accompanied the abundance 

figures for many other major and minor elements, 

were hardly more than guesses and had little analytical 

basis. It was not until the 1930's that emission and Xray fluorescent spectrographic techniques were sufficiently developed for practical determinations of these 

elements in low concentrations. Average percentages 

of the elements in the earth's crust (clarke values) 

for niobium and tantalum as estimated by various 

workers in geochemistry are listed in table 1. The

values of Georg Von Hevesy and coworkers, and of Ida 

and Walter Noddack were the first to be based on r"ial 

analytical determinations, but these values ranged 

lower than present day accepted values; however, the 

Noddacks' values were based chiefly on analyses of 

meteorites which are now known to contain less of 

these elements than most crustal rocks. The works 

of V. M. Goldschmidt and Kalervo Rankama forir ed 

the principal basis for modern values, near 20 ppm 

and 2 ppm for niobium and tantalum respectively. 

The monumental works of Rankama have been modified only slightly as methods and accuracy have improved. More recently A. P. Vinogradov and S. R. 

Taylor established clarke values for all the elements 

by combining the average values for particular elements in granite and in basalt. Vinogradov combined 

the elements in a 2:1 granite: basalt ratio, whereas 

Taylor used a 1:1 ratio. Such combinations of granite 

(or felsic rock) and basalt (or mafic rock) are considered by these geochemists to be representative of 

the earth's crust, and the values obtained for niobium 

and tantalum by this method compare favorably with 

the values obtained by Rankama by averaging analyses.

TABLE 1. Niobium and tantalum contents in the earths crust 

(clarkes) according to different authors

[Adapted from Rankama (1948)]

Author Nb (ppm) Ta (ppm) Nb : Ta

Vogt (1898) i -- - _. --__

Clarke and Washington (1924) 1. ----- . . . Vernadskii (1924) ^. .....................

Hevesy and others (1929) .....__---.._.

Hevesy (1932).. - ____--

Noddack and Noddack (1934) >....-._-

Goldschmidt(1937a).... .-- .-.--.-..

Van Tongeren (1938) L. ... _ . -. -_.

Rankama (1941) > __._.--_ .___-__

T?an1ramft flQdd^

Rankama (1948)------ ---..----_----.

Mason(1958)... ----.--------. .

Taylor (1964) .._ ----._ .

. .--. 1.0

-..-..- 30

------ 1-0.1

.._____. .04

- 40

..---.. .32

----- .. .3

_---.--- .0769

. . 15

.----.- 20

.----... 10

..---... 37

24

........ 24

20

.-- 20

1.0

.OOOn ._.

10-1

.012 -..

30

.24

.2

.0297

(15)?

5

13

2.1

2

2.5

2

1.33

1.33

1.5

2.6

1.33

2

F.07

11.4

F

1C

 Not listed in bibliographies of present report; see Rankama (1948).

Znamenskii (1957) pointed out that direct analytical 

determinations by Hevesy and coworkers are low because of (1) their not taking into account niobium and 

tantalum in biotite, (2) the rocks analyzed were not 

representative of the crust, and (3) niobium and tantalum were lost during chemical concentration procedures prior to analysis. Rankama's values, on the other 

hand, are slightly high because he assigned values equal 

to the limit of analytical sensitivity to samples in which 

these elements could not be detected.

LIMITATIONS OF DATA

The crustal averages, or clarkes, of niobium and 

tantalum and abundances of these elements in varions 

rocks are beset with the same uncertainty of accuracy
GEOCHEMISTRY OF NIOBIUM AND TANTALUM

and validity as are those for many other minor elements. 

Problems involved in the computation of crustal averages and the controversy as to the validity of methods 

of computation and accuracy of results were reviewed 

recently by Fleischer and Chao (1960) and Parker 

(1967). It should be pointed out that no practical 

method of sampling representatively the entire crust of 

the earth has yet been devised. Most attempts to approximate the average composition with respect to most 

elements are subject to criticism on the basis of bias and 

unrepresentative sampling. The crustal composition of 

some minor elements such as niobium and especially 

tantalum is even more in doubt than many others because of the limited availability of accurate analytical 

data, owing to the difficulty of analysis and other 

factors.

Limiting factors in the study of the geochemistry of 

niobium and tantalum are the availability of analytical 

data, the accuracy of analytical procedures, and the 

adequacy of sampling. In recent years, certain minor 

elements have been determined routinely in some 

analytical laboratories as a supplement to the determination of the major elements. Commonly niobium 

has been reported among those elements determined, 

but rarely has tantalum been detected because of its 

relatively high detection limits and low abundance in 

ordinary rocks. These routine analyses for niobium, 

though useful in petrologic studies, commonly have 

been of insufficient accuracy and sensitivity for geochemical use in establishing the abundance of the element and its geochemical behavior in geologic processes. 

It has been necessary, therefore, to make analyses of 

niobium and tantalum specifically for geochemical purposes because the required data for these elements simply do not automatically accumulate as byproducts of 

other analytical work, as is the case for many of the 

more easily detected elements. The effect of this limitation, of course, is a considerable reduction in the amount 

of data that otherwise would be available to geochemlsts.

Accuracy of analyses has improved considerably in 

recent years through research on methods and modern 

instrumentation and through use of standard samples 

exchanged among laboratories. Techniques of analysis 

now considered to be satisfactory for determination of 

niobium at low levels of concentration are: chemical 

colorimetry (or spectrophotometry) (Grimaldi, 1960), 

spectrochemical analysis, optical emission spectrography (Herz and Dutra, 1960), and X-ray fluorescence 

spectrography. Techniques of mass spectrography 

(Taylor, 1965a, b) have recently been introduced but 

are used in only a few laboratories on an experimental 

basis at the present time. Techniques of analysis with 

the required sensitivity for the determination of tantalum at the level of concentration found in ordinary

rocks are X-ray fluorescent spectrography (Fankama, 

1944) and optical emission spectrography following 

chemical concentration, chemical colorimetry (spectrophotometry) (Dinnin, unpub. data), neutron activation analysis (Atkins and Smales, 1960), and mass 

spectrography. It should be pointed out that various 

procedures of concentration, purification, or extraction 

of elements by wet chemical means are common to all 

of these techniques. The analytical chemistry of niobium and tantalum was reviewed comprehensively by 

Moshier (1964).

Accuracy among the above named techniques and 

among different analytical laboratories can be assessed 

from the compilations (Fleischer, 1965) of analyses of 

the standard granite G-l and standard diabase W-l 

listed in table 2. Though some deviations oc'mr, most 

of the niobium and tantalum determinations for G-l 

are close to 20 ppm and 1.6 ppni respectively and for 

W-l are near 10 ppm and 0.7 ppm respectively. Such 

correspondence between different techniques and anaTABLE 2. Analytical determinations of niobium and tantalum in 

standard granite G-l and standard diabase W-l

[Analytical data are in parts per million; a following number iu parentheses indicates 

the number of determinations averaged]

Method G-l W-l References; afiliation

Niobium

Chemicalcolorimetric-- 22 

Do-- ............ 22

Do-. ............ 23.1 (13) 10.2

SpectrochemicaL _-___ 18 ____

Do.

Do - .. J19

Spectrographic-__..-- 18.5

Do..--.. -- - 27 

X-ray fluorescence__.. 20

Mass spectrographic .. - - 4

Do-.--.. ...... 21

Do-.. --------- 20

Recommended values.. 20

(10) 10 (10) Grimaldi (1960); Ui-GS.

(3) 9 ( 9) F. S. Grimaldi (written commun.,

1961); U8GS.

(14) Esson (1966); Uuiv. Manchester. 

_ -.- Paul Barnett (written commun., 

1955); USGS.

-._-----._-. A. A. Chodos (written commun., 

1955); California list. Technology.

-_- A. T. Myers (written cornmuu.,

1958); USGS.

..-.-_ -. Herz and Dutra (I960); USGS, 

and Inst. Techaologia ludus., 

Belo Horizonte, Frazil. 

(18) 20 (20) Rooke and Fisher (1962); Univ.

' Leeds, England.

9 T. K. Ball (written commun., 

1964); Mineralog.-Geol. Mus., 

Oslo, Norway.

4 Brown and Wolsten'iolme (1964); 

Associated Elec. Industries, 

Ltd., Manchester. 

5.4 Taylor (1965a); Australian Natl.

Univ. 

4 Taylor (1965b); Australian Natl.

Univ. 

10 Fleischer (1965); USGS.

Tantalum

NeutroQ activation...-- 1.59 (8) 0.48 (2) Atkins and Smales (1960); Atomic 

Energy Research Establishment, Harwell, England. 

.... Do. 

. 93 (6) Morris and Olya (lf«0); Brunei

Coll., London.

Do_-__..-__- .9 (5)-.-__.... Butler and Thompson (1962);

Imperial Coll., Loudon.

Do-_- .-..-. 21.33 ( 2) 

Do.. - - 3.0 (8)

Do.-.- --_.__--- 1.3 (4) 

Do 

Mass spectrograp hie. - -. 2

Recommended values -. 1.6

. 69 (4) Hamaguchi and otl ers (1962);

Toyko Univ. Education. 

. 67 G. E. Gordon (written common.,

1967); Univ. Calif iruia, San

Diego. 

. 5 Brown and Wolsteubolme (1964);

Associated Elec. Industries,

Ltd., Manchester. 

.7 Fleischer (1965); US'GS.

1 Several.

2 Samples ground by these authors.
ABUNDANCE OF NIOBIUM AND TANTALUM

lysts inspires a high degree of confidence in niobium 

and tantalum analyses from most of the laboratories 

concerned.

A high degree of confidence, however, does not extend 

to all previously published analyses. Part of the analytical data on niobium and tantalum published within 

the last 10 years is of doubtful accuracy. Some of it is 

presented without any accompanying information on 

its accuracy, precision, or limits of sensitivity, and in 

some cases even the analytical method by which values 

were determined is not given. Such lack of qualifying 

information shakes the confidence of geochemists in 

part of the available data and promotes doubt as to the 

correctness of the geochemical interpretation based on 

these data.

The adequacy of sampling is a factor that is hardly 

possible to assess from the literature alone. Whether or 

not the samples are truly representative of the body or 

group of rocks that they are claimed to represent rests 

entirely with the sampler and is a factor of considerable 

variation. Some types of rocks are represented by averages of a large number of samples, whereas others are 

represented by only a few. Geochemical interpretation 

based on the latter can be of doubtful validity especially 

if, in a group of a few samples, some samples happen to 

be atypical. Sampling can be misleading if classification 

of the sampled rocks is erroneous or inaccurate. Complete chemical analyses are not always available for 

rocks analyzed for niobium and tantalum, so that petrographic classification of various degrees of refinement 

commonly is used instead of a more exacting chemical 

classification. The multiplicity of petrographic names 

and the differences among systems of classification 

limit the usefulness of the geochemical data derived from 

such samples.

ABUNDANCE IN BOCKS 

QTJALIFYINQ STATEMENT

No attempt has been made in this report to revise 

the clarkes of niobium and tantalum. Some figures, 

however, on the abundance of these elements in different 

types of rocks can be assembled from the data published 

in the last several years, and these figures, even though 

beset with the uncertainties mentioned above, give a 

more accurate picture of abundances than has been 

available previously. These figures can be expected to 

be revised subsequently as more complete and mo^e 

accurate data become available.

As compiled, the abundance figures of this report 

contain weaknesses and limitations against which the 

reader should be cautioned:

1. Some analyses probably are of low accuracy ard 

precision.

2. Some rocks are no doubt imprecisely classified.

3. Most averages representing complexes or areas are 

not weighted according to the relative abundance of 

the constituent rocks.

4. Some averages of rock types are not based on typical 

or representative rocks.

5. Analyses from certain regions predominate so that 

some averages are biased geographically.

6. Averages of most rock types are based on too few 

analyses.

The contents of niobium and tantalum in different 

types of rocks have been compiled by several authors. 

Mentioned here are Goldschmidt (1937b), Kankama 

(1948), Turekian and Wedepohl (1961), and Vinogradov 

(1962). The averages obtained by these authors are 

assembled in table 3.

TABLE 3. Average niobium and tantalum contents, in parts per million, in different types of rocks, as given by previous authors

Goldschmidt 

(1937b)

Rankama 1 (1948) Turekian and Wedepohl (1961) Vinogradov (1962)

Nb Nb Ta Nb:Ta Nb Ta Nb:Ta Nb Ta Nb:Ta

Monomineralic rocks. _ _

Mafic alkalic

Ultramafic. ___ _ _ _

Eclogite __ ____

Basalt _ _

Gabbro _ _ _

Diorite __ _

Granite, high Ca _ __

Nepheline syenite _ _

Clays, shales

Sandstone

Carbonate rocks

Deep sea carbonate _ _

Deep sea clay _ _ _ _ __

_________________ 0.3

_________________ 14

_________________ 16

_________________ 3

______ 8.0 19

_______ 24 3.6

----- i 40 21

35

.___ __ 160 315

_________________ 15

_________________ 8

______ _______ __ . 4

_________________ .6

0.7

1

1

. 7

1. 1

. 7

4.2

2

. 8

2. 5

<

0

.2

o

0. t

14

16

4

17

5

5

18

384

6

10

2

3

t ___ _ __

16.0

_ 19

/20

191

35

11

_ .OX

. 3

. 4.6

14

1. 0

1. 1

3.6

4.2

2. 1

8

OX _

OX _

ox _ X -

16. 0 1. 0 0. 018

17 20 . 48

_______ 20 .7

c a i

£ b \ 20 3. 5

17 _____.___-___.__-

14 20 3. 5

56 0

42

29

7

5.7

Recomputed from Rankama's data. 

296-315 68 2
6 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

A number of modern analyses for niobium and tantalum have been gathered from the literature during 

the present study. They are assembled under major 

rock types as follows: granite, quartz monzonite, and 

granodiorite, and volcanic rocks of similar chemical 

composition; sodic and alkalic granite and rhyolite of 

similar chemical composition; syenite and trachyte; 

nepheline syenite, phonolite, and other nepheline-bearing felsic rocks; other feldspathoidal rocks; gabbro, basalt, and alkalic basalt and gabbro; ultramafic rocks; 

sedimentary rocks; and meteorites and tektites.

IGNEOUS ROCKS

The abundance tables are useful in bringing out the 

relations between niobium and tantalum contents and 

the various types of rocks. Niobium is most abundant 

in alkalic rocks; namely nepheline syenite, syenite, 

and feldspathoidal rocks, and in alkalic mafic and 

ultramafic rocks. Niobium content is also high in sodic 

or alkalic granite. Within the alkalic group of rocks, 

nepheline syenite and mafic alkalic rocks carry the 

most niobium. Tantalum generally accompanies niobium, but the amount is about one-tenth to onefifteenth that of niobium in most rocks other than some 

nepheline syenites and related alkalic rocks. The 

abundance of tantalum is high in some of the Russian 

alkalic rocks but is extremely low in some niobiumrich alkalic complexes in other parts of the world.

Another factor of interest suggested by abundance 

tables is the variation of the niobium-tantalum content 

in similar types of rocks from massif to massif. In some 

comparisons there is actually greater difference between 

the content of these elements in rocks of the same 

general class from different massifs than between the 

average contents of contrasting rock types. As an example, nepheline syenite from the Lovozero massif, 

U.S.S.R., reaches niobium values of over 1,000 ppm, 

whereas nepheline syenite from the Shonkin Sag, 

Mont., ranges from 15 to 56 ppm. Averages in contrasting rocks range from 17 ppm in gabbro-basalt to 

173 ppm in nepheline syenite. Variations among alkalic 

complexes are shown by the average contents of niobium and tantalum in some nepheline syenite massifs 

of the U.S.S.R. (table 22). Niobium and tantalum contents range from about 900 ppm and 70 ppm respectively for the Lovozero massif as a whole to 100 ppm 

and 8 ppm respectively for the IPmen Mountains. 

Values near 100 ppm niobium are averages for the 

Khibina and Koisk massifs. All of these nepheline 

syenite massifs have niobium and tantalum contents 

that considerably exceed the clarke values.

The contents of niobium and tantalum in granites, 

quartz monzonites, and granodiorites are given in 

table 4 and summarized in table 5. Twenty-eight

plutons or occurrences have an average niobium content of 16 ppm, ranging from 0.9 to 39 pp^. This 

average value is slightly lower than those near 20 ppm 

calculated previously by Rankama, Turek; an and 

Wedepohl, and Vinogradov (table 3). Only a few granitic plutons have been analyzed for tantalum; 13 of 

them listed in table 4 average 1.3 ppm tantalum. 

These same 13 plutons average only 12 ppm niobium 

and their average Nb:Ta ratio is 9.2. Znamenskii 

(1964) proposed weighted values for Russian granites 

(Nb =14 ppm; Ta =1.1 ppm) which are close to these 

figures. Rhyolite, rhyodacite, and quartz latite from 

nine localities average about 28 ppm niobium rnd seem 

richer in niobium than their chemically equivalent 

plutonic rocks.

Sodic and alkalic granites represented by 20 plutons 

throughout the world range from 14 to 350 ppm niobium 

and average about 110 ppm (tables 6, 5). Twelve of 

these in which tantalum has been determined, 1 owever, 

average only 47 ppm niobium and 3.9 ppm tantelum and 

have an average Nb:Ta ratio of 12. Inasmuch as the 

analyses from the eight plutons excluded from the latter 

averages include some of the highest niobium values, 

their tantalum contents, if known, probably would 

raise the tantalum average considerably. Alkalic 

rhyolites from four localities range from 30 to 260 ppm 

niobium and average 97 ppm. Granites and rhyolites 

of these types are certainly enriched in niobiuir and the 

granites are enriched in tantalum. Although data are 

lacking, the rhyolites are probably enriched in tantalum 

also.

Considerable analytical data are available for niobium 

in nepheline syenites and phonolites, but a limited 

amount is available for tantalum. The latter element is 

almost entirely dominated by tantalum analyses from 

the Lovozero massif, U.S.S.R., and is subject to considerable regional bias. The Nb:Ta ratio si own at 

Lovozero may not be typical of other alkalic complexes. 

In fact, some minerals from complexes such as Magnet 

Cove and the Kaiserstuhl suggest that a much higher 

Nb:Ta ratio exists, but sufficient analyses are not yet 

available to show that the relation holds true for the 

alkalic rocks as a group. A great variation in niobium 

content in these rocks is shown in table 7, rang;ng from 

17 to 1,053 ppm; a meaningful average is difficult to 

obtain from such a spread of values. The average niobium content of nepheline syenite from 20 listed plutons 

or complexes is 173 ppm, but the average is about 149 

ppm if the rich Lovozero rocks are excluded (tables 8, 5). 

Three plutons or complexes in which both niobium and 

tantalum analyses are given average 135 ppm Nb and 11 

ppm Ta, and the Nb:Ta ratio is 12. These niobium 

values are considerably less, and the tantalum is 

greater than the values of Rankama (1944, 1948) for
ABUNDANCE OF NIOBIUM AND TANTALUM

TABLE 4. Niobium and tantalum contents of some granites, quartz monzonites, and granodiorites, and volcanic rocks of similar chemical

composition

Rocks, location

Number of

analyses or

samples represented

Nb

(ppm)

Ta

(ppm)

Nb;Ta ratio References

Plutonic rocks

Granite, granodiorite, Kalba, U.S.S.R ___ __ _

Kulinda, Baikal region, U.S.S.R _ _

central Kazakhstan, U.S.S.R__ _ _

Susamyr batholith, U.S.S.R __ _ _ ___

Alaskite granite, Slyudyanka, U.S.S.R __ _____

Granite, Mamsk-Chuesk, Bodaibensk, U.S.S.R 

Mamsk-Oronskii complex, U.S.S.R __ _

Konkudero-Mamakanskii, U.S.S.R __ _

Kalbin, E. Kazakhstan, U.S.S.R _____

Korosten, Ukraine, U.S.S.R __ __ ___

Urik-Oka, E. Sayan Mtns., U.S.S.R __ 

Kaibsk, Kazakhstan, U.S.S.R- __ _ _ _

Quartz monzonite, Rubidoux Mtn., Calif __ __ _

Granite, G-l standard _ __

Fennoscandian ___ _ _ _

Granite (rapakivi), Finland ____ ______ ___

Granodiorite, granite, etc., Kokchetav uplift.

U.S.S.R.

Do_______.___________. _________________

Alaskite, leucogranite, etc., Kokchetav uplift,

U.S.S.R.

Granite and microgranite, S. Rhodesia__ __

Granite, Paraguay_____

Aplite, Paraguay. _ ____

Granite aplite, Montana. _

Quartz monzonite, Montana

Quartz porphyry, Idaho. _ _

Granite porphyry, Idaho. _

Alaskite, Idaho____

Granite, Idaho. ___ ____

Granodiorite, California _____

Quartz monzonite, California _

Granite, California _ __ _ ___

Granodiorite, Johnston County, Okla_ __

Average _ _ _ _ ___ ____ __ __.

Average, analyses with both Nb, Ta re- .

ported.

3 .

1 .

1 _

190

9

11

14

7

4 

20

2

12

9

99

31

68

6

1

2

4

4

1

1

1

1

2

5

2

5

24. 0

2.4

0.9 

1.2

1. 0

17

10

12 

16

5.4

20

7

39

25.4

20 .

37 .

!96 _

10 .

20 .

13 .

7 .

28 .

28 .

15 .

20 .

20 .

20 .

15 .

20 .

16 _

12

1 2.0

1 16

i 8.2

1.9

2 <0. 8

<0. 4 

<0. 5

<0. 5

2. 1

<1. 1

<0. 8 

1. 1

0.42

1.6

3 5. 8

3 1.7

1.3

__________ Kuz'menko (1964, table 203).

__________ Do.

__________ Do.

12. 0 Gerasimovskii and Karpushina

(1965), Znamenskii (1964).

___ _ Znamenskii (1964).

Do. 

__________ Do.

_______._. Do.

8 Do.

____-.____ Do.

-__-_.____ Do.

15 Do.

13 Gottfried, David (U.S.G.S.;

written comm., 1965).

13 Fleischer (1965).

1. 2 Data averaged from Rankama

(1944, 1948).

23 Do.

_-__-.___. Podol'akii and Serykh (1964) .

__________ Do.

__________ Do.

___ ___- _ Cox and others (1965).

__________ Eckel (1959).

__________ Unpub. data, U.S. G.S.

__________ Do.

__________ Do.

__________ Do.

__________ Do.

.____-___. Do.

__________ Do.

__________ Do.

__________ Do.

__________ Do.

__________ Do.

9.2

Volcanic rocks

Rhyolite, S. Rhodesia __ __ _ _

Pitchstone, Iceland. __ _ __

Rhyolite porphyry, Paraguay. _ ___

Rhyolite and quartz latite, OregonRhyolite, eastern Idaho__ __ _ _ _ _ _

northwestern Wyoming _

New Mexico ___ ___ _____ _______

Rhyodacite-dacite, quartz latite, New Mexico. __

Rhyolite, Nevada __ _ __ __ _ _ ________ _

Quartz latite, Craters of the Moon, Idaho. __

Quartz latite porphyry, Nevada. __ _

Average ______________

3

31

1

3

7

8

12

15

15

2

9

1 110 _

23 .

10 .

30 .

56 .

30 _

33 _

29 .

26 _

1 300 _

18 -

28

..____ _ . Cox and others (1965) .

_ _____ _ Carmichael and McDonald (1961).

___--_-___ Eckel (1959).

__________ Unpub. data, U.S. G.S.

__________ Hamilton (1966).

____ _ __- Hamilton (1963).

__________ Unpub. data, U.S. G.S.

__________ Do.

__________ Cornwall (1962).

_---__-__ Unpub. data, U.S. G.S.

Do.

1 Not included in averages.

2 Figures shown as < are averaged at half value.

3 Some figures given by Rankama asl ess than a certain value were averaged at half that value.
8 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

TABLE 5. Abundance of niobium and tantalum in different magmatic rocks

Nb (ppm) Ta (ppm) Rocks, location Nb:Ta

Average Range Average

Granites, quartz monzonite, granodiorite (table 4):

28 plutons or occurrences_____-______________-____________________ 0. 9-39 22 ____________________________

13plutons__________________________________________-_----__ .9-39 12 <0. 4-5. 8 1.3 9.2

Rhyolite, quartz latite, rhyodacite, and pitchstone (table 4):

9 different areas____________________________________ 18-56 28 ______ ____________

Sodic and alkalic granites (table 6):

20 plutons.____-_ __________________________________._._ 14-350 109 ________________________

12 plutons (included above)______---_____________-_-____------__- 14-150 47 1-9.2 3." 12

Sodic and alkalic rhyolites (table 6):

4 different areas.________________________________-__ 30-260 97 ________________ ___.

Nepheline syenite and related rocks (tables 7, 8):

20 plutons or complexes..____________________________. 44-628 173 ______ ______

5 plutons or complexes_-___-_----__________-_-_-_-_-_-__----------------------_-_---- 4-52 21 ________

3 complexes (excluding Lovozero)__________________________________ 44-250 135 4-21 11 12

Lovozero (average for massif)___________________________ 320-1053 628 29-94 52 12

19 plutons or complexes (excluding Lovozero)_______-_______---_--__ 44-410 149 ____________________________

Syenites and trachytes (table 9):

15 analyses-.-_____________________________________ 20-210 95 ______._______________

4 analyses, different areas____________________________ 105-210 154 8.7-18 14 11

Gabbroic and basaltic rocks, tholeitic, etc. (table 11):

16 analyses or averages, different areas_______________________-_-__- 2.3-35 17 _____-_--_____________--_---

7 analyses or averages, different areas._____._______..__. 2.2-29 9 .19-2.8 . P 10

Gabbroic and basaltic rocks, alkalic (table 11):

10 analyses or averages_________________________________-_-_-_-_-_ 20-113 73 ____________________________

Feldspathoidal rocks (table 10):

20 analyses___--________._____________________________________ 13-1016 199 __________________________

Ijolite-meltiegite____________._________________________________ 1016 ____________ 90 11.3

Ijolite-urtite (Lovozero)__________________________________________ 572 _______ 54 10.6

Ultramafic rocks (table 12):

Kimberlites, 3 areas_____________--_--__________-_____-__--_----__ 94-240 ____-_-_-_-__-_____-_---_______-----

Olivinites, Kola Peninsula _____-_-___________-___-___-_---_-_-_-- .6-1050 ________ <. 6-82 ______________

Pyroxenite, Kola Peninsula-___--___-_____--__________-__--_---__- 5.4-379 ________ .55-47 ________________

Pyroxenite, Iron Hill, Colo__-_-_-_____________________-_-_------____-----_-_ 255 ____________________________

Alkalic ultramafic rocks, Kola Peninsula___________________---__-___ 134-518 ________ 13.2-59.6 ________________

TABLE 6. Niobium and tantalum contents of some sodic and alkalic granites and rhyolites of similar chemical composition 

Rocks, location i Nb (ppm) Ta (ppm) Nb:Ta References

Alkalic granite, Kola Peninsula, U.S.S.R __ ______ __ .

Do

Alkalic granite, Kiev, Kola Peninsula, U.S.S.R- __ _ _

Do____ ____________ _

Soda granite, Lunyo, Uganda ____ ____ ___

Alkalic granite, Liruei, Nigeria _________

Amo, Nigeria ___ ______ ___

Mount Tremont, N. H_ __ _

Hastingsite granite, Jackson Falls, N. EL _______ _

Alkalic granite, Kungnat, Greenland _

Rockall, N. Atlantic.-- _____ _ ____

Biotite granite (Conway), Redstone, N. H _ __ _

Alaskite, Ognitskii complex, U.S.S.R. (3)_ _ ___ _

Riebeckite granite, Ognitskii complex, U.S.S.R. (3)

Ognitskii complex, U.S.S.R. (4) _

Albite granite, Attu Islands, Aleutians (1)

Riebeckite(?) granite, Wichita Mountains, Okla. (20) _ _

Riebeckite granite, Brewster County, Tex. (!)_____

Mount Rosa, Colo. (3) _ ___ __

Conway, N. H. (2) _ _ _ __ _ _

Average. ____ ___ __ ____

Average, analyses with both Nb and Ta reported

Alkali rhyolite, soda rhyolite, New Mexico (20) _ _ _

Alkali rhvolite, Oregon _ _ _ .___ ____ .__

Riebeckite rhyolite, Brewster, County Tex. (7) ______ __

Jeff Davis County, Tex. (2)_ _ _

Platonic rocks

.___. 14

_____ 30

_____ 26

_____ 35

___ 350

___ 80

_____ 70

__ 150

_ __ 50

_____ 275 _.

_____ 150

_____ 50

_____ 17.3

_____ 13.7

_____ 22.7

_____ 30 _.

_____ 71 __

_____ 250 __

_ __ 267 _.

_____ 225 __

_____ 109 __

_____ 47

Volcanic rocks

_____ 61 __

__ _ 30 __

_ _ 260

_____ 35 _.

1.3

2.3

2.5

3.5

6.5

5. 1

8. 1

4.3

9. 2

1. 6

1.0

1.0

3.9

10.7

13

10.4

10

12

14

6.2

35

5.4

10. 8

13.7

22. 7

12

Gerasimovskii and Karpushina (1965) .

Do.

Do.

Do.

Knorring (1960).

Butler and Smith (1962).

Do.

Do.

Do.

Do.

Do.

Do.

Kovalenko and others (1964).

Do.

Do.

Unpub. data, U.S.G.S.

Do.

Do.

Do.

Do.

Do.

Do.

Unpub. data, U.S.G.S.

Do.

Do.

Do.

Average._________________________________________ 97

i Numbers in parentheses refer to number of analyses averaged.
ABUNDANCE OF NIOBIUM AND TANTALUM 9

TABLE 7. Niobium and tantalum contents of some nepheline syenites, phonolites, and other nepheline-bearing felsic rocks

Eocks, location'

Nb 

(ppm)

Ta 

(ppm) Nb:Ta References

Miaskite, Vishnevye Mts., U.S.S.R_-___-__-___________________ 250 21 12 Es'kova (1959).

Nepheline syenite, Borsuksai, U.S.S.R___--__-___-_-_____-____ 410 20 20 Kuz'menko (1964, table 203).

Il'menMts.,U.S.S.R______._________________ 110 8 13 Do.

hydrosodalite syenite, Lovozero, U.S.S.R. (18)._ 320 29 11 Gerasimovskii and others (1966).

Foyaite, Lovozero, U.S.S.R. (20)_________-_-__________________ 702 49.5 14.4 Do.

Lujavrite, Lovozero, U.S.S.R. (21)___________________________ 607 59 10.3 Do.

Amphibolelujavrite, Lovozero, U.S.S.R. (7)____________________ 760 52 14.6 Do.

Eudialyte lujavrite, Lovozero, U.S.S.R. (16)__________________ 1053 94 11.2 Do.

Porphyritic lujavrite, Lovozero, U.S.S.R. (5)__-___-____-__-___ 440 33 13.3 Do.

Do__________________________________________ 980 85 11.5 Do.

Poikilitic sodalite syenite, Lovozero, U.S.S.R. (6)________________ 490 32 15.3 Do.

Phonolite, Lovozero, U.S.S.R___-__---__--_---_________-_____- 399 37.5 10.6 Do.

Pseudoleucite phonolite, Lovozero, U.S.S.R---________--_______- 530 50 10.6 Do.

Nepheline syenite, Karasyrsk, U.S.S.R,________________________ 160 <10 ________ Es'kova (1960).

Tatarsk, U.S.S.R___________________________ 140 ________________ Do.

Karsk, U.S.S.R__-_________-________-__-___. 100 ________________ Do.

Foyaite, Khibina, U.S.S.R____________________________._______ 140 ________________ Borodin (1955).

Khibinite, Khibina, U.S.S.R._______________________________ 56 ________________ Do.

Rischorrite, Khibina, U.S.S.R_______________________________ 56 ________________ Do.

Nepheline syenite, Kishingar, India.___________________________ 44 4 11 Gerasimovskii and Karpushina

	(1965).

Shonkin Sag, Mont________________________ 25 ________________ Gottfried and others (1961).

Aegirine syenite, Shonkin Sag, Mont___________________________ 42 ________________ Do.

Aplitic syenite, Shonkin Sag, Mont.___________________________ 43 ________________ Do.

Transition rocks, Shonkin Sag, Mont. (3)_______________________ 20 ________________ Do.

Mafic phonolite, Shonkin Sag, Mont___________________________ 22 ________________ Do.

Nepheline syenite, White Mountain Plutonic-Volcanic Series, N. H__ 179 ________________ Do.

Sericitized syenite, Bearpaw Mts., Mont________________________ 400 ________________Pecora (1962).

Sericitized syenite dike, Bearpaw Mts., Mont__ _________________ 60 _____-__--____-_ Do.

Nepheline syenite, Iron Hill, Colo_______----_____-_----______ 150 ________________Temple and Grogan (1965).

Nepheline syenite, Arkansas bauxite region.____________________ 200 _______________-Gordon, Tracey, and Ellis (1958).

Do__'_____________________________________________ 100 ________________ Do.

Pulaskite, Arkansas bauxite region______------_____-_-___--____ 90 ________________ Do.

Feldspathic trachyte, Magnet Cove, Ark______________________ 200 _______________-Erickson and Blade (1963).

Pseudoleucite syenite, Magnet Cove, Ark_ ______________________ 74 ________________ Do.

Nepheline syenite, Magnet Cove, Ark__________________________ 99 ________________ Do.

Pseudoleucite syenite, Magnet Cove, Ark_______________________ 96 ________________ Do.

Nepheline syenite, Magnet Cove, Ark._________________________ 87 ________________ Do.

Tinguaite, Magnet Cove, Ark_________________________________ 220 ________________ Do.

Sodalite trachyte, Magnet Cove, Ark_________________________ 200 ________________ Do.

Nepheline syenite, Monchique, Portugal 2 ______________________ 420 .8 525 Rankama (1944, 1948).

Phonolite, Unterwiesenthal, Germany 2 _ ________________________ 200 .8 250 Do.

Kaiserstuhl, Germany (5)__-__---_--_______---__-__- 400 ________________Wambeke and others (1964).

tinguaite, Kaiserstuhl, Germany (10)_________________ 285 ________________ Do.

Nepheline syenite, Greenland (6)______________________________ 73 ________________Upton (1964).

Wheatland County, Mont. (3)______-________- 44 ________________Unpub. data, U.S.G.S.

Marathon County, Wis. (3)_________.________ 175 ________________ Do.

Fremont County, Colo. (3)_________________ 107 ---------------- Do.

Phonolite, Chouteau County, Mont. (4)______________________ 20 ________________ Do.

Meagher County,' Mont. (2)_________________________ 75 ________________ Do.

Leucite phonolite, Sweetwater County, Wyo. (17)________________ 58 ________________ Do.

Average ________________________________________________ 235 ________________

Average, Lovozero massif__ _______________________________ 628 52 12

Average excluding Lovozero massif___-_-_-_________________ 134 ________________

1 Numbers in parentheses refer to number of analyses averaged.

2 Values for these rocks not Included in averages.

nepheline syenite, which incidentally are based on 

analyses of only two samples.

Syenites and trachytes also have niobium and tantalum contents which are considerably higher than 

clarke values (tables 9, 5). Analyses from 16 different 

occurrences give an average niobium content of 95 

ppm; however, for four different areas, analyses in 

which both niobium and tantalum are given average 

154 ppm niobium and 14 ppm tantalum, and the 

Nb:Ta ratio is 11. Most of these analyses are of rocks

from alkalic complexes and perhaps should correctly 

be averaged with the nepheline syenites.

Melanocratic and leucocratic feldspathoidal rocks 

such as ijolites, urtites, and others, characteristically 

are high in niobium, but some of these rocks from 

Magnet Cove, Ark., for example, contain as little as 

20 ppm niobium (table 10). Twenty analyses or average 

analyses from different alkalic complexes average 

about 200 ppm and range from 13 to 1,016 ppm niobium. 

The average tantalum contents of ijolite-urtite and
10 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

TABLE 8. Niobium and tantalum contents of nepheline syenites 

and phonolites from different massifs

[Data summarized from table 7]

Massifs represented 1

Lovozero. U.S.S.R. (10).-... _. ..... . . .

Vishnevye Mts., U.S.S.R. (1). _._.._...___ ......

Borsuksai, U.S.S.R. (2)........ ..._- _. ..

Il'men Mts., U.S.S.R. (1)____ _.... _________

Shonkin Sag, Mont. (11).... .... ..............

White Mountain Plutonic-Volcanic.. .... ......

Series, N. H. (1).

Iron Hill, Colo. (I).... _ _____________________

Karasyrsk, U.S.S.R. (1) _ ____________________

Tatarsk, U.S.S.R. (I).......... . ..........

Koisk, U.S.S.R. (1). __._._.___._.________.__.

Khibina, U.S.S.R. (3)._.-_____________________

Kaiserstuhl, Germany (10)..__ _ . _ .... __

Tugtutoq, Greenland (6). _______ _ __ --.-..

Wheatland County, Mont. (3) ______ . ..

Marathon County, Wis. (3)..-. ___ ___ ....

Fremont County, Colo. (3) ____ __ . __ .

Average excluding Lovozero massif- _ _ .

Nb Ta 

(ppm) (ppm)

fiOQ £O

44 4

.---. 250 21

 . 410 20

....... 110 8

.---. 25 ...........

_______ 230 .... .....

....... 150 ___________

130

._____. 140 ...........

 -_.. 160 <10 .

140

._____. 100 ...........

_______ 85 .....

. ... 285 ..........

....... 73 .. ...

._.____ 44 _____.__-_

....... 175 ...........

. 107 ..

. ... 173

....... 149 ..

Nb:Ta

12

11

12

21

11

* Numbers in parentheses refer to number of analyses or types of rocks averaged.

ijolite-melteigite rocks from the Lovozero massif are 

54 ppm and 90 ppm, respectively, and the Nb:Ta 

ratios average about 11.

Two groups of gabbroic and basaltic rocks are distinguishable by their niobium contents (table 11). One 

group, which includes tholeiitic basalts, contains an 

average niobium content of 17 ppm (16 occurrences). 

Seven occurrences in which both niobium and tantalum 

were determined have averages of 9 ppm niobium and 

0.9 ppm tantalum, and a Nb: Ta ratio of 10. The other 

group, which includes alkalic basalts and gabbros, 

contains a much higher average niobium content of

73 ppm. Values range from 20 to 113 ppm. No tantalum 

analyses are available.

Ultramafic rocks show considerable variation in niobium and tantalum even in similar types from the 

same province (table 12). It is difficult to d:<4inguish 

alkalic and nonalkalic types. Peridotites tend to contain very low contents of both elements. A Kola 

Peninsula peridotite contains 5.5 ppm niol^um and 

0.49 ppm tantalum and has a Nb:Ta ratio of 11. 

Olivinites from Kola range from a fraction of 1 ppm 

niobium and tantalum to 1,050 ppm niobium and 82 

ppm tantalum, the latter rocks containing abundant 

titanomagnetite. Pyroxenites range from 5.4 ppm niobium and 0.55 ppm tantalum (Nb:Ta«10) from the 

Kola Peninsula to 255 ppm niobium from Iron Hill, 

Colo. Kimberlites contain high abundance levels of 

niobium, averaging 94 and 160 ppm for parts of the 

U.S.S.R. and 240 ppm for Basutoland.

SEDIMENTARY ROCKS

The abundance figures of niobium and tantalum in 

sedimentary rocks are listed in table 13. Highest niobium contents are found in deep-sea manganese nodules 

and sediments and in bauxites. Highest tantalum contents are found in marine clays and bauxite, although 

the high Nb:Ta ratio in deep-sea deposits indicates the 

paucity of tantalum in the deep-sea environment. Because of the chemically resistant nature, high specific 

gravity, and hardness of some of the common niobiumtantalum minerals, as well as the similar nature of 

some common minerals of titanium and zirconium, 

these minerals commonly are locally enriched in sandTABLE 9. Niobium and tantalum contents of some syenites and trachytes

Rock, location »

Biotite syenite, Vishnevye Mts., U.S.S.R.. ___ _____

Aegirine syenite, Vishnevye Mts., U.S.S.R. _ _ _ _

Nordmarkite, Greenland _ _____________ __ ___

Syenite, Kola Peninsula, U.S.S.R- _ _ __ ____ ___

Trachyte, Guadalupe Island __ _ __ ___ __ __ ____ ___

Do _ -___ _ .._- __ __ _

Trachyte, Hocheifel, West Germany (5)__ ______

Trachyte, Magnet Cove, Ark __ _______ ___ ___ _

Do _ _

Biotite syenite, Il'men Mts., U.S.S.R __ _ ____ __ _ __

Syenite, Chouteau County, Mont. (4)_ __ _________ _

Brewster County, Tex________ __ _ _ _ _

Fremont County, Colo. (4)____ __ _____ _

Trachyte, Meagher County, Mont. (2)__ _____ ___ _ ___

Brewster County, Tex. (6) _ __ ___ _ __ ____

Potash trachyte, Uganda- __ __ ______ _ ___

Average___.______________ _ _ _____ ____ _ __ __

Average with both Nb and Ta reported __ _ _ __

Nb

(ppm)

_________ 170

_.______. 130

_________ 105

_________ 210

___ _ 120 _

______ _ 140 .

_________ 95 _

-___-____ 100 _

_--.-_.__ 20 _

_________ 77 _

____ __ _ 20 _

__-__-___ 88 _

_________ 25 _

_________ 20 _

_________ 100 _

--_ ___ 2 400 _

_________ 95 _

_________ 154

Ta

(ppm)

16

12

8.7

18

14

Nb:Ta Reference

11 Es'kova (1959).

11 Do.

12 Gerasimovskii and Krrpushina

(1965).

12 Do.

. ___ ._ Engel and others (1965).

________ Do.

. _ -_. Huckenholz (1965).

. _ .._ Erickson and Blade (1963).

.____.._ Do.

_______ Es'kova (1964, table 187).

_______ Unpub. data, U.S. G.fT.

._._____ Do.

.._.____ Do.

..______ Do.

.-._____ Do.

_______ Sutherland (1965).

11

1 Numbers in parentheses refer to number of analyses averaged.

2 Not included in average.
ABUNDANCE OF NIOBIUM AND TANTALUM 

TABLE 10. Niobium and tantalum contents of some feldspathoidal rocks

11

Rocks, location i Nb (ppm) Ta (ppm) Nb:Ta Reference

Essexite, Illamaussaq, Greenland _

Jactipirangite, Magnet Cove, Ark_ 

Ijolite, Magnet Cove, Ark______

Do _____ ______ ______

Melteigite, Magnet Cove, Ark______________________ _______

Ijolite-melteigite, Lovozero massif, U.S.S.R. (2) _____________

Ijolite-urtite, Lovozero massif, U.S.S.R. (ll)____---_________

Ijolite, Khibina, U.S.S.R-___- ____ _______ ____ ____ _ _

Iron Hill, Colo _ ___________ __ _______ _ ___ __ _

Essexite, Kaiserstuhl, Germany (3) ________________________

Tephrite, Kaiserstuhl, Germany (5) ________________________

Essexite porphyry, monchiquite, Kaiserstuhl, Germany (5) _ . 

Bergalite, Kaiserstuhl, Germany (2) __ ____________________

Mpndhaldeite, gauteite, shonkinite, Kaiserstuhl, Germany (5). 

Olivine nephelite, Kaiserstuhl, Germany (5) . __-_-___---_____

Shonkinite, Shonkin Sag, Mont. (2) ________________________

Do _ --__ _----_-__ _-_--- ____.

Shonkinite, Paraguay (2) _________________________________

Chouteau County, Mont. (2) ___________________

440 ________________ Gerasimovskii and Karpushina

(1965).

20 ______________ Erickson and Blade (1963).

50 _ _ ___ Do. 

150 ________________ Do.

20 ________________ Do.

140 _____________ Do.

1016 90 11.3 Gerasimovskii and others (1966X 

572 54 10. 6 Do. 

210 ___--__-_-_---._ Borodin (1955). 

250 ______________ Temple and Grogan (1965).

128 ----__________ Wambeke and others (1964).

115

105

430

140

75

15

13

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do.

65 _______----____- Eckel (1969).

20 _______-_--__-_. Unpub. data, U.S.G.S.

Average.__________----_________________---_--________ 199

Range____________________________________________ 13-1016

1 Numbers in parentheses refer to number of analyses averaged.

TABLE 11. Niobium and tantalum contents of some gabbroic, basaltic, and alkalic basaltic rocks

Rock, location 1 Nb (ppm) Ta (ppm) Nb:Ta Reference

Gabbro and basalt

Basalt, Bombay, India___________________________________ 29 2. 8 10 Gerasimovskii and Karpushina (196?).

Olivine basalt, Guadalupe Island. _________________________ 30 ________________ Engel and others (1965).

Gabbro, Skaergaard, Greenland (9)________________________________ .92 _______ Atkins and Smales (1960).

Gabbro (San Marcos), southern California (3)_____________ 4.7 .19 25 Gottfried, David (written commun.,

	1965). 

W-l diabase, Centerville, Va______________________ 10 . 7 14 Fleiseher (1965).

Tonalite, southern California (2)_________________________ 5.3 .45 12 Gottfried, David (written commun.,

	1965). 

Gabbrcndiorite, Chernogor massif, Siberia_________________ 9.8 1 10 Gerasimovskii and Karpushina (1965).

Gabbro, Kpkchetav uplift, U.S.S.R._______________ 7 ___________ Podol'skii and Serykh (1964).

Diabase, Victoria Land, Antarctica (2)_____________________ 20 ________________ Hamilton (1965).

Diorite pegmatite, Victoria Land, Antarctica (!)_____________ 30 ________________ Do.

Gabbro, Victoria Land, Antarctica (3)_________--_---_____ 20 ________________ Do.

Basalt, andesine basalt, New Mexico (8)__________________ 26 ________________ Unpub. data, U.S.G.S.

Diabase, Nevada (2)________.._____________________ 35 ______________ Do.

Basalt Nevada (2)_______________________________ 25 ______________ Do.

Snake River, Idaho (5)_________________________ 14 ________________ Do.

Dolerite, Siberian Platform, U.S.S.R. (10) 2_________._ 3. 2 .46 7 Znamenskii and others (1965).

Basalt, Siberian Platform, U.S.S.R. (18)_______________ 2.2 .48 4.6 Do.

Average.___-----__--__--_--____---_-_-_-_-----_-___ 17 ________________

Average in which both Nb and Ta are reported________ 9 . 9 10

Alkalic basalt and gabbro

Alkalic basalt, eastern Pacific Ocean (4)____________________ 75 ________________ Engel and others (1965).

Alkalic olivine basalt, Hocheifel, Germany (7)__-__-_-_-___ 65 ________________ Huckenholz (1965).

Hawaiite, Hocheifel, Germany (4)_________________________ 69 ________________ Do.

Mugearite, Hocheifel, Germany (3)________________________ 84 ________________ Do.

Hauyne alkalic basalt, Hocheifel, Germany.________________ 110 ________________ Do.

Analcime olivine metagabbro, Magnet Cove, Ark.__________ 20 ________________ Erickson and Blade (1963).

Theralite, Meagher County, Mont-_--.____.___-_______ 61 __________ Unpub. data, U.S.G.S.

Basalt, Southern Rhodesia (4)___________________________ 91 ________________ Cox and others (1965).

Paraguay (2)_________________________ 45 _._________ Unpub. data, U.S.G.S.

Trachybasalt, Tristan da Cunha (14)__._______-._______ 113 _________-_--_ Baker and others (1964).

Average.__---__-_----_-----____----____----_---____ 73 ________________

1 Numbers in parentheses represent number of analyses averaged.

2 Weighted average representing 162 samples.
12 GEOCHEMISTRY OF NIOBIUM AND TANTALUM 

TABLE 12. Niobium and tantalum contents of some ultrarnafic rocks

Rocks, location Nb (ppm) Ta (ppm) Nb:Ta References

Olivinite, Kola Peninsula, U.S. S.R.__ .

Titanomagnetite olivinite, Kola Peninsula, U.S.S.R____

Olivinite, Kola Peninsula, U.S.S.R_____ _____

Kola Peninsula and Karelia, U.S.S.R__ _ _

Biotite olivine rock, Harzburg, Germany ____

Peridotite, Kola Peninsula, U.S.S.R _ ______

Alkalic ultramafic rocks, Kola Peninsula, U.S.S.R _

Pyroxenite, Kola Peninsula and Karelia, U.S.S.R _

Pyroxenite, Kola Peninsula, U.S. S.R_ _

Do._____________________. ________________ _____

Nepheline pyroxenite, Kola Peninsula and Karelia.

U.S.S.R.

Pyroxenite, Kola Peninsula, U.S.S.R.

Pyroxenite, Iron Hill, Colo _ _ _ _

Do._____________________________ _____________

Kimberlite, U.S.S.R. (349)_____. ____________________

Yakutia, U.S.S.R. (57) _ ________________

Basutoland (14) _ _ _ _

0.6

1050

7

394

56

5.5

134-518

379

202

5. 4

290

220

94

160

240

<0. 6

82

. 62

45. 6

4. 2

.49

13. 2-59. 6

47. 3

25

16

18. 7

. 55

13

11

8.7

13

11

8. 7-10. 2

8. 0

10. 8

10

. Rankama (1944, 1948).

Do.

Gerasimovskii and Karpushina

(1965).

Kukharenko and others (1965).

Rankama (1944, 1948).

Gerasimovskii (1965).

Kukharenko and others (1961).

Kukharenko and others (1965).

. Kuz'menko (1964, table 203).

Do.

Kukharenko and other? (1965).

Gerasimovskii and Karoushina

(1965).

. Temple and Grogan (1P65).

Do.

. Kudrvavtsev (1964).

. Burkov and Podporina (1965).

_ Dawson (1962).

i Numbers in parentheses refer to number of analyses averaged.

stones and conglomerates. Such accumulations, which 

constitute placers and fossil placers, are not listed in 

the table.

ABUNDANCE IN METEORITES AND TEKTITES

Ten samples of meteorites, including both the stony 

and the iron types, were analyzed by Rankama (^1944, 

1948). Only two samples of the stony meteorites had 

detectable niobium (0.3 and 2.1 ppm). None of the 

iron meteorites had niobium and none of the 10 samples 

had tantalum detectable by Rankama's methods. 

Atkins and Smales (1960) and Ehmann (1965), using 

neutron activation, determined the tantalum content 

of several chondritic meteorites to average 0.023 and 

0.021 ppm respectively. The tantalum content of iron

meteorites is at least an order less than that for stony 

meteorites, ranging from 0.0008 to 0.005 ppm (Atkins 

and Smales, 1960). Unfortunately, the niobium contents of these samples have not been determined; 

therefore, the Nb:Ta ratio cannot be computed. Vinogradov (1962) estimated the niobium and tantalum 

contents of chondrites to be 0.3 ppm and 0.02 ppm 

respectively and the Nb:Ta ratio to be 15. (See table 

14.)

Ehmann (1965) also analyzed several tektites for 

tantalum by neutron activation. (See table 14.) These 

tektites range from 0.56 to 3.3 ppm tantalum, roughly 

in the range of ordinary rocks. So far as is known, no 

data on their niobium contents are available.

TABLE 13. Niobium and tantalum in some, sedimentary rocks and other rocks or deposits1

Material Number of Nb (ppm) Ta (ppm) Nb :Ta 

samples

References

Deep-sea sediments 4

Clay and sand sediments

Arid-environment clavs, Russian Platform

Humid-environment clays, Russian Platform

Clays, average for Russian Platform

Manganese nodule, Albatross _ _ Manganese nodule core, Indian Ocean

Manganese nodule, outer shell, Indian Ocean

Bauxite. Arkansas

___. 17

____ 8

..._ 18

____ 10

.___ 5

_ _ _ _ 199

____ 155

____ 354

_ _ 1

1

____ 1

__ _ 1

4

25

o

.___ 46

12

. 4

.6

40

20

10

16

13.3

20. 1

IS. 3

35

147

7. 6

29

35. 6

27. 7

38

450

1.4

2

o

1

<? Q

<4

. 9

2 4

2

2. 3

. 17

5. 1

4. 4

5

8. 6

>7

3

40

14.8

8.4

9. 1

3.3

170

7

6.3

7.6

Rankama (1944, 1948). 

Do. 

Do. 

Do.

Goldschmidt (1937b). 

Rankama (1944, 1948).

Do.

Pachadzhanov (1963). 

Do. 

Do. 

Rankama (1944, 1948).

Do. 

Pachadzhanov and others (1963).

Do. 

Pachadzhanov (1964).

Do.

Rankama (1944, 1948). 

Gordon and Murata (1952): 

Fleischer and others (1952>.

1 Includes sandstones, clays, shales, bauxites, etc.

2 Includes iron ores and calcareous sinters.

s Includes limestones, cherts, coals, lignites, etc.

4 Includes clays, oozes and manganese nodules.
ISOMORPHOUS SUBSTITUTION 13

TABLE 14. Niobium and tantalum contents of meteorites and

tektites

Nb 

(ppm)

Ta 

(Ppm)

Reference

Silicate meteorites

Rhodite, Mikkeli - . _

Olivine enstatite chondrite, Lake Labyrinth.

South Australia.

Johnstown, Colo _ -- ___ ____ _ - _ .

Ness County, Kans ________ - ___ _

Long Island, Phillips County, Kans-. _ . ...

Forest City, Iowa. _ ._ _ ... ___ .... . Chateau Renard __ _- -- - - __ -... --- -

Holbrook, Ariz. _ _ . - _ __ .. -. ... . .

Chandakaphur . __ . . ._ _____ ..

Bjurbole. _ . ____ ... _ . ___ . __ ..

Tabory (Ochansk) __ ... ___ . _____ . Average for preceding 8 chondrites- ....... 

Average for 10 chondrites. - - .. ___ ..

Vinogradov's average t ---. --. _ _ .

0.3 ... ..

2.1 ..........

... .... 0.008

----- .022

----- .027

__--_- .023

--__- .027

__ - .025

 .. .020

. .021

 -- .018

.- __ .023 

....... .021

.3 .02

. Rankama (1948).

Do.

Atkins and Smales

(I960).

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do. 

Ehmann (1965).

Vinogradov (1962).

Iron meteorites

Canyon Diablo.__ -__.__.__ _._____ 0.002 Atkins and Smales

Henbury... 

San Martin.

(1960). 

. 005 Do. 

.0008 Do.

Tektites

Philippinite, Isabella site.________________ 0.74 Ehmann (1965).

Pugad Babuysite....____._____ 3.3 Do. 

Thailand tektite, Kan Luang Dong (un- ____ .61 Do. 

strained type).

Kan Luang Dong (ordinary .___ .56 Do. 

type).

ISOMORPHOUS SUBSTITUTION

Isomorphous substitution of niobium for tantalum 

in most minerals of these elements is well illustrated by 

the minerals listed in the glossary of this paper. Substitution in a more limited degree by niobium and 

tantalum for elements such as titanium, tin, tungsten, 

zirconium, and others is also well known in a host of 

minerals. It therefore seems appropriate to delve more 

deeply into the principles involved in isomorphous 

substitution and the nature of substitution as applied 

to these elements.

Isomorphous substitution (diadochy) among trace 

elements and their behavior during crystallization has 

been discussed in detail by Ringwood (1955a, b), and 

some of Ringwood's ideas have been applied by Herz 

and Dutra (1964). This slightly different approach to 

the subject of isomorphism seems appropriate for discussion here. In prior work, Goldschmidt (1937 a, 1954) 

proposed the following rules governing the substitution 

of ions which relate the size of ions and their charges:

1. For two ions to be able to replace one another in a 

crystal structure, the ionic radii must not differ 

by more than 15 percent.

2. When two ions that possess the same charge but 

different radii compete for a lattice site, the ion 

with the smaller radius is preferentially incorporated.

296-315 68 3

3. When two ions that possess similar radii but different 

charges compete for a lattice site, the ion vith 

the higher charge is incorporated.

Ringwood noted that Goldschmidt's rules did not 

always apply, and suggested that these rules do not 

adequately consider the partial covalent bonding that 

coexists with ionic bonding in most lattices. To allow 

for the partial covalent bonding, Ringwood utilised 

the property of electronegativity (Pauling, 1940) and 

thus formulated the following rule (Ringwood, 19£5a, 

p. 193) :

Whenever diadochy in a crystal is possible between two elements possessing appreciably different electronegativities, the 

element with the lower electronegativity will be preferentially 

incorporated because it forms a stronger and more ionic bond 

than the other.

Ringwood found that the Goldschmidt rules commonly 

applied where electronegativities were nearly the same, 

but the above rule was applicable where electronegativities differed by one-tenth or more.

Ionic potential is a property closely related to electronegativity and can be used to express the same general 

relations inasmuch as it is a relative measure of icmc 

or covalent character of the chemical bond also. Ionic 

potential is defined as the cation charge, z, divided by 

the ionic radius, r, or z/r and is a value more convenier tly 

computed than electronegativity. Ionic radii, electronegativities, and ionic potentials of niobium, tantalum, 

and some related elements are given in table 15.

TABLE 15. Physical constants of some elements

Element

Atomic Ionic 

number Charge radius 

(A)

Electro- Ionic 

nega- potential 

tivity '

Aluminum

Titanium _ ..............

Vanadium...... .- _ .

Do..................

Iron. .....................

Do..... ...........

Zirconium. .-....----.....

Niobium. ................

Molybdenum-- _ .......... 

Tin... ....................

Hafnium......- ........

Tantalum..... .........

Tungsten _ . . . . ..........

Do 

...... 13

...... 22

...... 23

...... 23

...... 26

...... 26

...... 40

...... 41

42 

...... 50

...... 72

 ... 73

...... 74

74

+3

+4

+3

+5

+2

+3

+4

+5

+4 

+4

+4

+5

+4

+6

0.51

.68

.74

.59

.74

.64

.79

.69

.70 

.71

.78

.68

.70

.62

1.5

1.6

1.4

1.9

1.7

1.8

1.5

1.7

1/6 

1.8

1.3

1.5

1.6

2

5.88

5.88

4.06

8.48

2.71

4.69

5.07

7.25

5.71 

5.64

5.13

7.35

5.71

9.68

1 Gordy and Thomas (1956).

Most univalent, divalent, and some of the larger 

trivalent ions of trace elements during crystallization 

exist free in the magma; and their crystallization can 

be interpreted satisfactorily in terms of ionic rad'us, 

ionic charge, and electronegativity or ionic potential 

according to the rules of Goldschmidt and of Ringwood 

that were given above. Ions with charges greater than tl °<se 

and some of the smaller trivalent ions, however, form 

complexes with oxygen, hydroxyl, fluorine, chlorne, 

and other anions, and these complexes maintain their
14 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

identity during the crystallization process. Complexforming ions reflect properties of the individual complexes more than they reflect properties of the central 

cation during crystallization (Kingwood, 1955b).

Elements whose ionic potentials are greater than 

4.80 tend to form complexes, and the higher the ionic 

potential the more stable are the complexes formed. 

Values of ionic potential in some complex-forming 

ions range from Ga+3 =4.83 to Cr+3 =25; Nb+5 andTa+5 

have intermediate values (7.25 and 7.35 respectively). 

Cations of highest ionic potential seldom dissociate in 

the magma; however, cations such as Si+4, Nb+5, and 

Ta+5, have high enough values to form stable complexes 

but, on the other hand, are also in the range of values 

where partial dissociation under certain conditions is 

possible.

Elements whose ionic potentials are less than 2.70 

occur as free ions in the magma and do not form 

complexes, whereas elements ranging between 4.80 

and 2.70 are transitional, behaving either as free ions or 

as complex formers depending on the composition of 

the magma.

The structures of most minerals crystallizing from 

magmas are based upon SiO4 tetrahedra linked in 

various ways. Therefore, trace element complexes in 

the magma may either replace SiO4 tetrahedra in 

silicate minerals or precipitate as separate phases. 

Kingwood modified the Goldschmidt rules to apply to 

diadochy between trace-element complexes and SiO4 

tetrahedra as follows:

1. On geometric grounds only complexes of the tetrahedrally coordinated type can substitute for SiO4 .

2. The larger the change on the central cation the 

smaller will be the tendency for tetrahedrally 

coordinated complexes to replace SiO4 tetrahedra.

3. The larger the size of the cation the smaller will be 

the tendency for tetrahedrally coordinated groups 

to replace SiO4 tetrahedra.

Pentavalent niobium and tantalum probably can 

form both the tetrahedral complexes, NbO4~3 and 

TaO4~3 , and the octahedral complexes, NbO6~7 and 

TaO6~7 . Although both forms possibly exist in the 

magma, the octahedral form is the one found in most 

niobium-bearing minerals. For example, the structure 

of some oxide minerals such as perovskite and columbite 

are formed basically from linked octahedrally coordinated groups and contain no tetrahedral groups at all. 

These octahedra are composed of titanium, iron, 

niobium, tantalum, and other cations in sixfold coordination with oxygen ions. Another niobium-bearing 

mineral, sphene, is made up of both tetrahedral and 

octahedral groups linked together with calcium ions 

filling the interspaces. The tetrahedra are SiO4 groups

and the octahedra contain titanium, niobium, tantalum, 

and other elements as central cations.

Neither the tetrahedral nor the octahedral complexes of niobium and tantalum would be easily incorporated into silicate minerals in substitution for the 

SiO4 tetrahedral complexes if Ringwood's rules apply. 

The octahedral complexes would be ruled out on the 

basis of geometry alone, although substitution in 

octahedral positions in some silicate minerals is possible 

(for example, niobium in muscovites, probably in the 

aluminum position). Tetrahedral complexes of niobium 

and tantalum would be difficultly incorporated also 

because of the higher charge and considerably larger 

size of the niobium and tantalum cations with respect 

to the silicon cation. Hence, niobium and tantalum 

complexes would tend to accumulate in some felsic 

magmas during crystallization until sufficiently concentrated to allow precipitation, most likely as multiple 

oxide minerals. In some other magmas, especially 

mafic ones, however, these elements probably would 

tend to be scavenged by crystallizing accessory minerals 

of titanium or titanium and iron and thus would be 

dispersed and not concentrated during crystallization.

Although niobium, tantalum, titanium, zirconium, 

tin, tungsten, and other similar elements posHbly are 

present in magmas as complexes with oxygen, hydroxyl, fluorine, and other anions, and may enter or 

form minerals in part as complexes, these elements can 

be considered as individual ions for the purpose of 

examining schemes of isomorphism and the electrostatic balances involved.

There are two types of isomorphism isovalent and 

heterovalent (Kuz'menko, 1959). Isovalent isomorphism 

means the substitution of ions of similar ionic radius 

and the same ionic charge; heterovalent isomorphism 

is the substitution of ions of similar size but differing 

ionic charges.

The common mutual substitution of niobium and 

tantalum in most minerals of these elements is the 

isovalent type of isomorphism. The ions of these two 

elements are so similar in their properties that one 

seldom occurs in nature to the complete exclusion of 

the other.

Heterovalent isomorphism is extensive between 

niobium-tantalum and titanium, as well as1 among 

other elements such as zirconium, tin, tungsten, and 

some others. Where such substitution occurs the 

overall electrostatic neutrality of the mineral is preserved by the simultaneous substitution of ions of 

greater or lesser charge in other parts of the crystal 

lattice or by the development of lattice deficiencies or 

vacancies in either oxygen or cation positions (Aleksandrov, 1963).
ISOMORPHOUS SUBSTITUTION 15

Schemes oi heterovalent isomorphism in niobiumtantalum minerals have been pointed out by many 

authors, notably Rankama (1944, 1948), Kuz'menko 

(1959, 1961), Es'kova (1960), and Kukharenko, Skrizhinskaya, Vainshtein, and Kakhana (1961). Some 

schemes of substitution that apply in either a major 

or minor degree in niobium-tantalum-bearing minerals 

are listed in table 16.

TABLE 16. Schemes of isomorphous substitution in niobiumtantalum-bearing minerals

Scheme Example

Ti

(Nb,

(Nb, Ta)+5+(Fe, Al)«<-» 

2(Nb, T

Loparite, perovskite. 

Sphene, irinite. 

Biotite. 

Rutile, tapiolite.

Zr

(Nb,

2(Nb,

2(Nb,

(Nb,"

(Nb,

, Zr)+«+(Th,

Wohlerite, zircon.

Polymignyte.

Zirconium betaftte.

Zircon.

Zircon, baddeleyite.

w

(Nb, Wolframite.

Sn

2(Nb, Cassiterite.

AI, Si, Fe

(Nb, Ta)«+2(Mn, 

(Nb, T

(Nb, 

(Nb,

Iron oxides.

Pyroxenes, amphiboles. 

Aegirine. 

Muscovite. 

Muscovite.

Others

(Nb, Ta)+5+Liti«-M 

(Nb, Ta)+«+(Ce, La)««-2Th+* 

(Nb, Ta)+5 -j-Si«-«P+5+Ce« 

(Nb, Ta)«+2Si+4 2P+5+RE+3

Biotite, lepidolite. 

Thorite. 

Monazite(?). 

Erikite.

i RE=rare-earth elements.

An example is given in the table for each scheme, 

though some schemes apply to a great number of 

minerals, and more than one scheme may apply to the 

same mineral.

The most prevalent substitution of niobium and 

tantalum is for titanium. The close association of these 

elements has been long recognized. Fleischer, Murata, 

Fletcher, and Narten (1952) pointed out that the content of niobium was greatest in titanium minerals from 

alkalic rocks and granitic pegmatites and least in 

those from ordinary gabbro and anorthosite. Examination of the formulas of niobium-tantalum minerals in 

the glossary section of this report shows that a large 

proportion of these minerals have titanium as an

integral part, commonly in isomorphous substitution 

for niobium and tantalum. Titanium minerals in which 

niobium and tantalum proxy for titanium are sphere, 

rutile, ilmenite, perovskite, and many others listed in 

the glossary. Certain pyroxenes, amphiboles, and titaniferous micas have been shown to contain minor 

amounts of niobium and tantalum, presumably also 

present in the titanium position in the lattices of these 

minerals. The average atomic ratio of niobium to 

titanium in titanium minerals is about 1:3,000 and 

the ratio of tantalum to titanium is 1:7,000 (Hevesy 

and others, 1929).

The substitution of niobium and tantalum for 

zirconium in some minerals is also well known. Minerals known to contain small amounts of niobium and 

tantalum include zircon, eudialyte, catapleiite, lavenite, 

baddeleyite, and others. According to Goldschmidt 

(1954, p. 504) the average ratio of niobium to zirconium 

is about 1:10 in granites, liparites (rhyolites), syenites, 

trachytes, nepheline syenites, and phonolites.

Niobium and tantalum substitute also in certain 

tungsten and tin minerals, and minor amounts of 

tungsten and tin are found in many niobium-tantalum 

minerals. Wolframite is a common tungsten mineral 

and cassiterite is a common tin mineral containing 

these substituted elements. The presence of minor 

scandium in some wolframite apparently compensates 

for the electrostatic disequilibrium caused by minor 

niobium-tantalum incorporated in the structure. Some 

wolframites and cassiterites are known to be mixtures 

of these minerals and columbite-tantalite (Grigor'ev 

and Dolomanova, 1951).

Kuz'menko (1959) mentions minor substitution of 

niobium and tantalum as charge-compensating elements in the substitution of phosphorus for silica in 

such minerals as monazite, erikite, and rhabdophare. 

Substitution in minor amounts for thorium, cerium, 

and lanthanum in the minerals steenstrupine, hydrocerite, and thorite is also proposed, but the great 

difference in the ionic radii of these elements as well as 

the difference in charge suggests the difficulty of such 

substitution.

GEOCHEMICAL BEHAVIOR 

MAGMATIC BOCKS

Niobium and tantalum are commonly dispersed in 

magmatic rocks as camouflaged elements in iron- and 

iron-titanium-bearing minerals and to a certain extent 

in zirconium minerals; rarely, under specific conditions, 

independent minerals of niobium and tantalum are 

formed. Many rock-forming minerals have been shown to 

contain smaU amounts of these elements (see Glossary), 

but as noted by several authors, pyroxenes, amphiboles, 

micas, sphenes, titanium-iron oxides, and zircons con-
16 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

tain most of the niobium and tantalum that is sparsely 

disseminated throughout large igneous rock masses.

Niobium and tantalum generally tend to accumulate 

and increase in abundance in the later differentiates and 

crystallates during differentiation of magmas (Goldschmidt, 1954, p. 500; Kuz'menko, 1959; Butler and 

Smith, 1962; Podol'skii and Serykh, 1964). Characteristically in a series of comagmatic rocks, the contents 

of these elements increase from ultramafic and mafic to 

the more silicic and alkalic rocks, and in late magmatic 

and postmagmatic products such as pegmatites, aplites, 

greisens, and carbonatites these elements are concentrated in greatest amounts.

Niobium and tantalum tend to be concentrated in 

certain magma types. Alkalic rocks normally contain 

more niobium and tantalum than other rock types, and 

certain alkalic granites and metasomatized(?) biotite 

granites contain sufficient niobium-tantalum to have 

formed independent niobium-tantalum minerals such 

as pyrochlore, columbite-tantalite, fergusonite, and 

euxenite.

The abundance of niobium and tantalum varies also 

to a certain extent from one petrographic province to 

another. Similar classes of rocks in different provinces, 

as well as province averages, differ greatly in their 

abundance values, either exceeding or being less than 

clarke values.

The behavior of niobium and tantalum in granitic 

rocks, alkalic rocks, alkalic ultramafic rocks, pegmatites, 

greisens and veins, and carbonatites is discussed below.

GRANITIC ROCKS

The geochemical behavior of niobium and tantalum 

in granitic rocks depends to a certain extent on the 

paragenesis of the titanium minerals in which these 

elements are dispersed and on the types of granite 

involved. Znamenskii and coworkers, in discussing 

dispersion and concentration of niobium and tantalum, 

considered two major types of granitic rocks: (1) 

monazite-bearing granites commonly containing ilmenite and rutile, and (2) allanite-bearing granites 

containing sphene and magnetite. These authors, in 

a series of papers (Znamenskii and others, 1957; 

Znamenskii and others, 1962, Znamenskii and Popolutov, 1964), pointed out the contrasting geochemical 

distribution of niobium and tantalum in these two 

types of granite and interpreted some of the magmatic 

processes involved on the basis of these facts.

In monazite-bearing granites containing ilmenite 

and rutile, most of the niobium and tantalum is concentrated in accessory biotite. For example, in the 

Kalbinsk massif of eastern Kazakhstan 60-86 per ent 

of the niobium and 50-72 percent of the tantalum are 

concentrated in the biotite of the rocks, which incidentally also contains most of the titanium in the rocks. 

(See table 17.) It should be noted that the Umenite in 

these rocks contains much higher percentages of 

niobium and tantalum than the biotite, but the latter 

is so much more abundant that it is the principal 

carrier of these elements.

In allanite-bearing granites containing sphene and 

magetite, however, most of the niobium and tantalum 

is concentrated in the sphene, with subordinate amounts 

concentrated in biotite. This suggests that th e calcium 

content of the whole rock may be an important factor 

in determining the distribution of niobium and tantalum among the rock-forming minerals.

In granite of this type from the eastern Sayan Mountains only 16-60 percent of the niobium and up to 38 

percent of the tantalum in the rock is in biotite, whereas 

35-85 percent of the niobium and 60 percent or more 

of the tantalum is in sphene. Most of the titanium of 

the rock is contained in biotite. (See table IS,)

Gottfried and Dinnin (1965) showed that most of 

the tantalum in the southern California batholith 

occurs in the biotite and its coexisting hornblende. 

(See table 19.) The southern California rocks are not 

amenable to classification under Znamenskii's scheme 

because these rocks range in composition from gabbro 

to granite. In tonalite from the batholith, biotite contains the predominant percentage of tantrlum, but 

in granodiorite from the batholith, hornblende and 

biotite share the tantalum almost equally. In the 

quartz monzonite, the hornblende contains more 

tantalum than the biotite, although both minerals 

are enriched in tantalum as compared to thes<?- minerals 

in the tonalites and in the granodiorite of the batholith. 

In all rocks from the batholith, sphene, magr etite, and 

ilmenite play a relatively insignificant role in the distribution of tantalum, principally because of their low 

abundance in the rocks compared with biotite and 

hornblende.

It should be emphasized that the granites and 

other rocks mentioned above do not contain high 

levels of niobium or tantalum; in fact, some have 

levels below the clarke values.

Certain rare varieties of granite contain independent 

minerals of niobium and tantalum as accessories, 

which in some granites are sufficiently abundant to be 

characteristic. Such granites are the source of some of 

the world's commercially important residual and 

placer deposits of niobium and tantalum. These 

granites may be classed as columbite granites, euxenite 

granites, fergusonite granites, or pyrochlore granites, 

and they all apparently are monazite-ilmer ite-rutilebearing types. According to Pavlenko, Chung-Yang, 

and Morozov (1960), columbite, euxenite, and fergusonite granites are all highly aluminous-; having
GEOCHEMICAL BEHAVIOR 17

TABLE 17. Distribution of niobium and tantalum in granitic rocks of the Kalbinsk massif, U.S.S.R.

[After Znamenskii and others (1957)]

Content of Nb and Ta in mineral Amount of Nb and Ta Percent of total Nb Total content of Nb and T,i in

Content of phases in analyzed mineral and Ta from data on rook bulk

Mineral mineral in rock fractions minerals

Nb (ppm) Ta (ppm) Nb:Ta Nb (ppm) Ta (ppm) Nb Ta Nb (ppm) Ta (ppm) Nb'Ta

Porphyritic biotite granodiorite, Asu-Bulak

_________ 13.00

_________ .30

..__.._._. .26

96. 0 7. 6 12. 0 12. 5 1.0 

860. 0 130. 0 6. 6 2. 6 .4 

70.0 110.0 .__.___._._-_... .3 .

_. _____________ ... 15.1 1.7

60.0 

12. 5

72.5

50.0 _______-_-__-__--__--_.

20.0 ____.___-_______-_-_-__

15. 0 __ ______ _ _____ ._

85. 0 21 2. 0 10. 5

Porphyritic biotite granite, Mlroliubovsk Ridge

Ilmenite. ________

Sum_ ___.

_________ 8.00

__________ .17

130. 0 18. 0 7.2 10. 1 1. 44 

1200. 0 210. 0 5. 8 2. 1 .36 

. __ ___________________ 12.2 1.80

68. 0 

140 

82.0

65.5 _ ___ _ _ _____ _____

16.5 _______________________

82. 0 15 2. 2 6. 8

Coarse-grained biotite granite, Mount Batch

Sum___ __..

....___... 5.6

_________ .05

200. 0 26. 0 7. 7 11. 2 1. 45 

3600. 0 640. 0 5. 6 1. 8 .32 

________________________ 13.0 1.77

86.0 

14.0 

100. 0

72.5 ___ _____ _______ __

16.0 _______________________

88. 5 13 2. 0 6. 5

Coarse-grained biotite granite, Chur-Chut-Su

Ilmenite____ _ _.

Sum __ ___.

TABLE

Mineral

.._...-._. 8.1

. _. . . .1

80. 0 9. 5 8. 4 6. 5 0. 77 

1700. 0 260. 0 6. 5 1. 7 .26 

_ _____________________ 8.2 1.03

65. 0 

17.0 

82.0

59.0 _______ _ _______ _

20.0 ________ _ _ _______ _

79.0 10 1.3 7. 7

18. Distribution of niobium and tantalum in granitic rocks from the eastern Sayan Mountains, U.S.S.R. 

[After Znamenskii and others (1962)]

Content of 

mineral in 

rock 

(percent)

Nb and Ta contents in Amount of Nb and Ta(in 7) 

mineral in given mineral per gram 

of rock

Nb (ppm) Ta (ppm) Nb Ta

Percent of total Nb and Ta Total Nb and Ta content 

bound in a given mineral in rock (ppm)

Nb» Ta * Nb Ta

Coarse-grained biotite granite (no. 126)

Biotite_ __ ____ .

Sphene______ __.

Total ___ .

..___._._. 4.5

--__-____ .25

145 3. 9 6. 53 0. 18 

1550 115 3. 88 . 29 

_______ ___ ____ 10.41 .47

59.6 

35.4 

95.0

38.4 ___________________

61.6 -_--__-___-__--_-__

100. 0 11 <0. 7

Coarse-grained biotite granite (no. 152)

Sphene. _________

Total ___ .

8 2

_________ .5

37 <3. 5 3.0 <0. 28 

2400 200 12. 0 1. 0 

____ _____ _ _ __ 15.0 <1. 28

21.4 

85.6 

107.0

<22. 0 __ ____________ __ _

>78. 0 _____._-______--___

100. 0 14 1

Medium-grained biotite granodiorite (no. 113)

Sphene __ ______

Total ___ .

.-_.__-_.. 15.0

.-__--___. .3

29 <3. 3 4. 3 <0. 50 

1350 155 4. 0 .46 

____ ___ _ ___ _____ 8.3 <. 96

56.5 

52.5 

109.0

<50. 0 _ -_. _____ _---_

«50. 0 _ . ____ ___ ___

__________ 7.6 <\

Medium-grained biotite hornblende granodiorite (no. 149)

Total __ _

. _.- 8.0

7 4

7

12 <4 1. 0 <0. 32

1 O ____________________

705 58 5.0 .40 

_-___--__--______.__ 6.0 <. 72

16. 1

80.7 

96.8

<45. 0 _. ________ --_-_

>55. 0 ___________________

_______ 6.2 <\

' Percentage of the total Nb content in the rock.

* As distributed between biotite and sphene.

* Not determined.
18 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

TABLE 19. Tantalum in hornblende and biotite from igneous 

rocks of the southern California batholith

[After Gottfried and Dinnin (1965)]

Mineral Parent rock

Tantalum (ppm)

Chemical

Neutron 

activation

Distribution 

coefficient > Ta in biotite/

Tain 

hornblende

Hornblende.

Hornblende. 

Biotite.---.. 

Hornblende. 

Biotite-.....

Hornblende. 

Biotite......

Hornblende. 

Biotite.-..-. 

Biotite-.-...

0.7 

1.6

1.7

1.5 

2

Hornblende. 

Biotite.

Hornblende. 

Biotite.-..-.

Hornblende 

Biotite......

San Marcos Gabbro 

(hornblende norite).

> Green Valley Tonalite. _. |

I Lakeview Mountain f 

J Tonalite. I

JBonsall Tonalite..-_... [

\Woodson Mountain f

J Granodiorite. I 2

Woodson Mountain -.---.-...

Granodiorite.

1 Quartz rnonzonite, f 18 

/ coarse phase of Rubi- \ 6.6

doux Mountain.

\Quartz monzonite, I 10 

/ coarse phase of Eubi- I 4.8

doux Mountain.

1 Quartz rnonzonite, fine f 12 

I phase of Rubidoux I 6

Mountain.

0.17

1.64

2.3 

2.1 

1.7 

1

1.62

.8 1 

.4 )

1 Calculated from chemical analyses.

Al>(K+Na+2Ca). On the other hand, pyrochlore granites are highly alkalic, or agpaitic, having (K+Na)>Al. 

Normal allanite-sphene-biotite granite has the relation 

(K+Na)<Al<(K+Na+2Ca), and such granite commonly does not contain independent niobium-tantalum 

accessory minerals.

The columbite granites may not result entirely 

from magmatic processes, because columbite and some 

other accessory minerals are interpreted as formed by 

autometasomatic processes akin to greisenization. 

In the process of alteration of the normal biotite 

granite to columbite granite, calcium is removed from 

the plagioclase and iron, manganese, titanium, niobium, and tantalum are removed from the biotite. 

These elements are recombined to form fluorite, 

magnetite, and columbite. The notable biotite granites 

of the Jos Bukuru complex in Nigeria are of this 

type. The Lunyo albite granite of Uganda (Knorring, 

1960) and its associated aplites, pegmatites, and greisens 

have a characteristically high content of niobium, 

which is present in columbite. In addition, betafite is 

found in some of the pegmatites. The niobium content 

varies from 0.05 to 0.1 percent in the granite and from 

0.1 to 0.2 percent in the greisens, and in aplites and 

pegmatites it reaches 0.5 percent locally. In some 

respects, this granite resembles the albite-riebeckite 

granite of Nigeria. Present also are fluorite and the 

lithium-fluorine mica, zinnwaldite.

Euxenite and fergusonite granites owe the formation 

of their niobium-tantalum accessory minerals to late* 

magmatic crystallization. The hyperaluminous condition of these rocks is interpreted to have limited the 

entry of titanium, niobium, and tantalum into the 

biotite and hornblende during their crystallization

and caused these elements to accumulate in the rest 

magma and then to crystallize in late parr,genesis. 

Euxenite granite (quartz monzonite or quartz diorite) 

is known from the Idaho batholith, Bear Valley, 

Idaho (Mackin and Schmidt, 1956). Fergusonite 

granite occurs in the basin of the Gava Say River, 

U.S.S.R.

Pyrochlore granites are highly alkalic and ere composed principally of microperthite, sodic plagioclase, 

quartz, sodic amphibole, and sodic pyroxene. I Tiobium 

and tantalum apparently do not enter the lattices of 

such amphiboles and pyroxenes in sufficient degree 

to prevent the accumulation and late crystallization 

of these elements in pyrochlore. Granites of this type 

are the pyrochlore-riebeckite granite of Nigeria (Beer, 

1952; MacLeod, 1956) and the Mount Rosa Granite 

near Pikes Peak, Colo.

The ratio Nb:Ta is useful in showing the relative 

concentration of niobium and tantalum in various 

stages of magmatic differentiation, even though some 

of the ratios are extremely variable due to insufficient 

accuracy of some of the analyses. General trends in 

the NbrTa ratio between granitic comagmatic rocks 

show that, in differentiation, rocks of the rronaziteilmenite-rutile type are enriched in tantalum with 

respect to niobium, but that significant enrichment 

does not occur in rocks of the sphene-allanite type. 

For example, in the Kalbinsk massif, composed of the 

monazite-ilmenite-rutile-type rocks, the Nb:Ta ratio 

decreases from 10.5 in the early rocks to one in genetically related pegmatites and shows a progressive decrease in the ratio through successively younger 

differentiates between these extreme members of the 

massif.

On the other hand, in sphene-allanite-bearing 

granites sphene is the principal carrier of niob;um and 

tantalum. During magmatic stages of intrusion of 

this type rock, including the postmagmatio stage, 

apparently no significant enrichment in tantalum as 

compared with niobium occurs. Notable contents of 

niobium and tantalum do not appear in the pegmatites 

of this type of granite. From their study of the distribution of niobium and tantalum in granitic rocks, 

Znamenskii and Popolutov (1964) concluded that the 

presence of sphene in granitic rocks is not a favorable 

sign for widespread occurrence of niobium, and especially tantalum, mineralization in pegmatites derived 

from the same magma as such granites. Conversely, 

biotite granites without sphene are favorable for the 

formation of predominantly tantalum mineralization 

in genetic association with rare-metal pegmatites.

Such a generalization on lack of tantalum concentrations in pegmatites of sphene-bearing granites does not 

apply to the remarkable tantalum concentration at the
GEOCHEMICAL BEHAVIOR 19

Harding pegmatite, New Mexico (Montgomery, 1950). 

This pegmatite is related to the Dixon Granite of 

Just (1937) that contains abundant sphene (as much as 

4 percent) in areas 2 miles or more beyond the pegmatite; however, only traces of sphene are found in the 

granite surrounding the pegmatite. Tantalum that is 

dispersed in the granite is carried mostly in the sphene. 

The near absence of sphene in the granite surrounding 

the pegmatite is considered one of the principal factors 

in the concentration of tantalum in the pegmatite. 

Montgomery (1950, p. 865) stated,

specific absence of abundant Ta-bearing sphene, present in the 

same granite elsewhere, from all pegmatite-adjacent granite, 

which during crystallization of that granite may have freed, or 

left free, sufficient Ta from this source alone to supply the entire 

Harding enrichment.

Other attributive factors mentioned are: a genetically 

related tantalum-rich granite; some indirect wallrock 

control during pegmatite replacement that made 

available calcium needed to combine with tantalum to 

form microlite; a lack of tantalum-receptive minerals 

in both parental crystallizing granite and pegmatite; 

and a long-continued process of deformation fracturing 

that kept the pegmatite open to successive invasions 

of solutions from the granitic magma below.

ALBITIZED AND GREISENIZED GRANITIC ROCKS

Granitic rocks of the Ognitsk complex in the eastern 

Sayan Mountains, U.S.S.R., are metasomatically 

albitized and have high concentrations of niobium and 

tantalum (Kovalenko and others, 1964). The Nb:Ta 

ratio is lowest in the most intensely albitized zones, 

showing enrichment in tantalum with respect to niobium 

as a result of albitization. A sharp increase in the content of niobium in albitized and greisenized rocks was 

noted also by Podol'skii and Serykh (1964) in the 

Kokchetav uplift, Kazakhstan; however, Voloshin 

and Miletskii (1966) noted a decrease in niobium to 

almost nothing in the most hignly albitized Kazakhstan 

rocks such as albitites.

The relative distribution of niobium and tantalum is 

shown by Kudriii, Kudrina, and Shuriza (1965) to be 

complex in varieties of metasomatic rocks characterized 

by riebeckite, biotite, zinnwaldite, or cryophyllite. 

Niobium minerals in these rocks range in paragenetic 

sequence from euxenite and fergusonite to pyrochlore 

through three successive generations of columbite and 

show considerable variation in their relative niobiumtantalum contents. Early pyrochlore (data on fergusonite and euxenite not given), formed in the sodium 

stage of metasomatism, is characterized by a relatively 

high Ta2O5 content of about 6-7 percent and a Nb2 05 : 

Ta2O5 ratio of about 7.5-9. In the later columbite stages 

columbite I, associated with cryophyllite, topaz, and

cassiterite, is characterized by a lower Ta2O5 content of 

2-3 percent and a high Nb2Os:Ta2O5 ratio of 20-30; 

columbite II, closely associated with zinnwaldite, is 

characterized by a sharp decrease in the Nb205 :Ta2O5 

ratio to about 7-8; and columbite III, formed ir the 

stage of silicification, has a high ratio near 35. Tiese 

authors attribute the variation in the niobium-tantalum 

contents to the variation in physicochemical conditions 

at the time of formation of the respective minerals, 

especially the variations in alkalinity and acidity of the 

effective solutions.

Beus and Sitnin (1960, 1961) and Sitnin and Bykova 

(1962) have described the occurrence of niobium and 

tantalum in greisens and greisenized granites and pegmatites. They have noted the occurrence of microlite in 

addition to columbite-tantalite in greisenized granites 

and remark on the separation of niobium from tantalum 

and the tantalum enrichment in the process of alteration, albitization, and greisenization. The maximum 

concentration of tantalum is associated with the most 

intensely greisenized rocks, and these authors attribute 

the enrichment in tantalum and its separation from niobium to fluorine-bearing solutions that were active 

during greisenization. In a fluorine-rich environment, 

niobium and tantalum could combine with fluorine to 

form ionic complexes, and a separation of these elements could result from tantalum-fluorine complexes 

being more mobile and stable than niobium-fluorine 

complexes.

According to Sitnin and Razina (1963), biotite is 

gradually changed to lithium-bearing micas in the process of metasomatic formation of some amazonite-albite 

granites from biotite granites. Niobium and tantrlum 

are released from the biotite during this process to form 

independent niobium or tantalum minerals.

Greisenized rocks, high temperature quartz, and 

quartz-feldspar veins are often found beyond the boundaries of the parent intrusives. Such rocks commonly 

contain columbite, tantalum-bearing rutile, cassiterite, 

or wolframite (Beus and Sitnin, 1961).

GRANITE PEGMATITES

High concentrations of niobium and tantalum hi 

granite pegmatites are well known. Granite pegmatites 

are also the only known commercial source of tantalum. 

As mentioned previously, niobium and tantalum tend 

to be concentrated in the later products of crystallization of certain types of granite, and the rocks tend t o be 

enriched hi tantalum with respect to niobium. In most 

granites, independent accessory minerals of niobium 

and tantalum are not found, but in pegmatite phases 

of such granites a wide variety of niobium-tantalum 

minerals is commonly formed. Niobium and tantalum 

enter also to a certain degree into the structure of other
20 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

pegmatite minerals such as micas, garnets, tourmaline, 

Umenite, and zircon. Certain types of pegmatites seem 

to be more intensely mineralized with niobium and 

tantalum than others. These are commonly complexly 

zoned pegmatites with strong development of albite or 

lithium minerals.

Granitic pegmatites range from homogeneous, relatively unzoned pegmatites to heterogeneous, very 

complexly zoned and replaced pegmatites. Such peg-, 

matites have been classed as unzoned and zoned by 

Cameron, Jahns, McNair, and Page (1949). Niobium 

and tantalum minerals are found in both types, although 

these elements seem to be more prevalent in the zoned 

type, at least in pegmatites of the United States. 

Columbite-tantalite is the most common niobiumtantalum mineral in the relatively unzoned pegmatites, 

whereas the zoned pegmatites contain a wide variety 

of other minerals of these elements in addition to 

columbite-tantalite.

Niobium-tantalum enrichment is common in muscovites and other micas that were formed in the late 

stages of pegmatite crystallization. Odikadze (1958) and 

Heinrich (1962) demonstrated that muscovites in pegmatites with columbite and beryl contain appreciably 

greater amounts of niobium and beryllium than muscovites from pegmatites without these minerals. (See 

table 20.) Niobium-bearing pegmatites from the Petaca, 

New Mexico, and south-central Colorado districts contain muscovites averaging slightly over 400 ppm niobium, whereas the niobium-poor pegmatites of FranklinSylva, North Carolina, have muscovites that average 

only 94 ppm niobium. Niobium and tantalum are 

considered to be present in the lattice of the micas in 

isomorphous substitution for titanium and aluminum. 

In biotite, niobium and tantalum probably substitute 

for titanium with simultaneous substitutions of lithium 

for magnesium to preserve electrostatic equilibrium:

Mg+2+Ti+4< >Li+1 +(Nb,Ta)+s.

Muscovite contains only minor titanium so that substitution in the mineral probably occurs between

TABLE 20. Comparison of percentage of occurrence of niobium 

minerals in pegmatites with averages of niobium in accompanying 

muscovites

[After Heinrich (1962)]

District

Pegmatites

with Average Nb Number of 

columbite (percent) analyses 

(percent)

Petaca, N. Mex____ __ __.

South-central Colorado_______.

Black Hills, S. Dak _ ____ .

Franklin-Sylva, N.C. _ _ _ _ ..

87

17

17

»0.4

0. 0404

.0419

.0298

.0094

10

Q

10

10

> Samarskite.

aluminum (eight-fold coordination) and lithium, niobium, and tantalum:

>Li+1 +(Nb,Ta)+6 .

Kuz'menko (1961) suggests that niobium is preferentially taken into the mica structure leaving tartalum 

to accumulate and form independent minerals of its own 

such as microlite and tantalite. The presence of lithiumbearing micas in pegmatites has significance in the 

formation of separate tantalum deposits.

The enrichment of tantalum in successive later 

stages of crystallization of lithium-rich pegmatites is 

discussed by Beus and Sitnin (1961) from a different 

standpoint. In pegmatites showing evidence of strong 

lithium metasomatism in the late phases of pegmatite 

genesis, microlite or other high-tantalum-bearing minerals are formed, effecting in some deposits a nearly 

complete separation of niobium from tantalum. The 

high fluorine content of the lepidolite indicates the 

role played by that element in the alteration. Fluorine 

may be the primary factor in the enrichmert and 

fractionation of niobium from tantalum because of the 

difference in mobility between tantalum-fluorire and 

niobium-fluorine complexes, the probable form in which 

these elements were present in the pegmatite-forming 

fluids. As noted before, a similar process involving 

fluorine is ascribed to the separation of these elements 

in the formation of greisens.

The content of tantalum with respect to niobium 

tends to increase from the earliest to the latest phases of 

pegmatite development. This is shown in a general way 

by the increase of tantalum in columbite-tantalite 

from the walls inward in various zones of pegmatites 

(Cameron and others, 1949, p. 64; Page and others, 

1953, p. 58). Such an increase of tantalum from wall 

zones to cores of pegmatites as reflected by th^ progressive increase in specific gravity in cohrabitetantalite of the Quartz Creek district, Colorado, is 

shown in the following table (Staatz and Trites, 

1955, p. 40) :

Pegmatite

1234 _____ __

1234 __ ____-.

1574__ __ _____

452

205 __ ________

205_ __ _______

245 __ _______..

1557___________

Internal unit

_ ___ _do __ _____ ___ _____ _

__ Core __ ___ _______________

_._____do______________________

_______do_______________.______

do

Specific 

gravity

5.0

5.1

6.0

5.8

6.1

6.3

5.7

6.7

Rudovskaya (1964) has shown that the youngest 

granitic pegmatites in the northwestern part of the 

White Sea region, U.S.S.R., are progressively enriched
GEOCHEMICAL BEHAVIOR 21

in tantalum with respect to niobium and both of these 

elements are concentrated in independent niobiumtantalum minerals. These elements are also contained 

in small amounts in micas and cyrtolite. (See table 21.) 

Niobium-tantalum minerals of the same paragenetic 

sequence in the pegmatites of the region show an enrichment of tantalum from early columbite to tapiolite, 

microlite, and djalmaite, then a sharp decrease in 

tantalum with respect to niobium in the fergusonites 

that followed. This reversal in trend has yet to be 

explained.

A dispersal of niobium and tantalum, rather than 

concentration, has been noted by Slepnev (1964) in the 

extensively greisenized pegmatites of the Sayan Mountains, U.S.S.R. In the greisenized pegmatites, niobium 

and tantalum are dispersed in muscovite and cassiterite, whereas in those pegmatites not greisenized, 

these elements are contained in columbite-tantalite 

and a manganese-niobotantalate mineral. Muscovite 

of the greisenized pegmatites contains as much as 0.02 

percent niobium and 0.003 percent tantalum; the 

cassiterite contains 0.14-0.98 percent niobium and up 

to 0.68 percent tantalum. A reversal of the normal 

order of zoning is also suggested in some of the pegTABLE 21. Niobium and tantalum contents (percent by weight) 

in micas from pegmatites of different ages and from the enclosing 

rocks in the northwestern White Sea region, U.S.S.R.

[After Rudovskaya (1964)]

Locality NbaOs TajOs Rock

Biotite

Paiv-Oiva___ __ 0.003 <0. 001 Kyanite-garnet-biotite

Rikolatva __ _ _

Rikolatva-179--.-

Leivoiva

Rikolatva-179 ____ 

Rikolatva-198---- 

Rikolatva __

Lei voiva-4 _ _ _

Leivoiva-20 1 _ _ _ _ _

KhetaLambino.

Rikolatva- 198 ....

Leivoiva-4bis __ _

Rikolatva __

.003

.006 

.0094

.010

.007

0.006 

.002 

.008

.005

,006

.004 

.006

.013

.012 

.036

.033

<.001

0)

.004

.001

0)

Muscovite

<0. 001 

= .001

.001

.001

<.001

.004

.005 

.007

.010

Early pegmatite. 

Do.

Do.

Do.

Early pegmatite. 

Do. 

Do.

Do.

Do.

Do. 

Do.

Early pegmatite near

a later pegmatite 

dike. 

Do.

Do.

 Not found.

matites in which tantalite, instead of columbite, is 

characteristic of the outer zones and a mangane^eniobotantalate, poorer in tantalum, is found in the 

central zones.

NEPHELINE SYENITE

Nepheline syenites have been studied extensively by 

Russian geologists and Russian reports dominate the 

literature on these rocks. According to Es'kova (1960), 

nepheline syenite comprises about one percent of the 

igneous rocks of the U.S.S.R., and more than thirty 

massifs of this type of rock are known to occur there. 

In eight prominent nepheline syenite massifs the average niobium content ranges from 100 to 900 ppm and 

the average tantalum content ranges from 8 to 70 ppm. 

The Nb: Ta ratios vary from 12.0 to 20.5. (See table 22).

As in granitic rocks, niobium and tantalum of nepheline syenites are more highly concentrated in late phases 

of intrusives, that is, pegmatites, albitized zones, and 

carbonatites, and in late hydrothermal veins. Such 

enrichment is several to tens of times the niobium and 

tantalum contents of the parent rocks (Es'kova, 1960),

Russian geologists recognize two classes of nepheline 

syenites, agpaitic and miaskitic (Ussing, 1912; Gerasimovskii, 1956, 1960, 1963; Gerasimovskii and others, 

1957; Es'kova, 1960). Chemically these can be separated, 

on the basis of their ratios of total alkalies to alumina. 

The ratio (K2O+Na2O):Al2O3 is called the agpaitic 

coefficient, which exceeds 1 for agpaitic syenites and is 

1 or less for miaskitic syenites. Gradual transitions 

from one type of syenite to the other can occur even 

within a single massif.

Niobium occurs in a wide variety of minerals in 

nepheline syenites and the veins and other features 

connected with them. More than 40 minerals f,re 

known from agpaitic syenite but only about 20 have 

been found in miaskitic syenite (Es'kova, 1960).

The geochemistry of niobium and tantalum is d :fferent in massifs of agpaitic syenite than in those of

TABLE 22. Average contents of niobium and tantalum in so*ne 

massifs of nepheline syenite, U.S.S.R.

[After Es'kova (1960), except as noted]

Massif

Number of Average content (ppm)

averaged for 

massif Nb Ta

Ratio 

Nb:Ta

Lovozero_ _______

Do. i______

Vishnevye Gory__ 

Il'men Mountains. 

Borsuksai__ _ _____

Karasyrsk _______

Khibina. ________

Koisk_ __________

Tatarsk. ________

39

123

2

2

2

1

1

1

1

900

696

240

110

410

160

100

100

140

70

60

20

8

20

12.8

11.6

12

13,8

20.5

i Gerasimovskii and others, 

! Not determined.
22 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

miaskitic nepheline syenite. In the latter, niobium is 

concentrated not only in minerals of titanium and 

zirconium, but accumulates and forms independent 

minerals in late magmatic and postmagmatic derivatives. On the other hand, in agpaitic nepheline syenites, 

in spite of higher average contents of niobium and 

tantalum, these two elements are largely fixed in 

titanium and zirconium minerals (Gerasimovskii and 

Venkina, 1960; Gerasimovskii and others, 1959).

According to Es'kova (1960) in summarizing the 

relations in Russian alkalic massifs, niobium and tantalum are concentrated in agpaitic nepheline syenites in 

the minerals- loparite, murmanite, lomonosovite, belyankinite, ramsayite, lamprophyllite, fersmanite, rinkolite, lovchorrite, epistolite, nenadkevichite, shcherbakovite, gerasimovskite, sphene, eudialyte, lovozerite, 

catapleiite, and in other minerals of titanium and zirconium. The content of Nb2O5 in them ranges from 0.01 

to 44.9 percent. The minerals have low contents of 

Nb2O5 (commonly 1-3 percent, but as much as 10-12 

percent) in the nepheline syenite proper, in simple 

undifferentiated pegmatites, and in high temperature, 

fine-grained, equigranular zones of complexly replaced 

differentiated pegmatites. Highest contents of niobium 

are found in minerals of late stages of differentiated pegmatites that are genetically associated with late (?) 

phases of nepheline syenites. Some late zeolite veins and 

albitites contain minor pyrochlore, but the occurrence 

of such minerals is not characteristic. The contents of 

Ta2O5 in titanium and zirconium minerals of agpaitic 

nepheline syenite varies from 0.04 to 0.93 percent and 

the Nb :Ta ratio ranges from 5 to 95.

Niobium and tantalum are concentrated in rocks and 

veins of miaskitic nepheline syenites hi minerals of the 

pyrochlore group and aeschynite, and in ilmenite, 

ilmenorutile, fersmite, sphene, zircon, biotite, and rarely 

columbite, chevkinite, or others. The contents of Nb2O5 

and Ta2O5 in the minerals range from 0.003 to 71.5 and 

from 0.04 (where detected) to 8.65 percent respectively.

An increase in niobium and tantalum and a decrease 

in titanium can be demonstrated in minerals of miaskitic 

rocks representing magmatic and postmagmatic stages 

from nepheline syenite to pegmatites and to albitized 

and carbonatized rocks. For example, pyrochlore from 

miaskites and pegmatites contains 60-65 percent Nb2O5 

and 5-10 percent TiO2, whereas pyrochlore from carbonatite contains 71.5 percent Nb2O5 and 0.5 percent 

TiO2 . Pyrochlore from miaskites and early stages of 

pegmatites are characterized by small contents of 

tantalum (up to 1.5 percent Ta2O5); however, in the 

late stages of pegmatite formation, hydropyrochlore is 

formed with an increase in tantalum content (up to 4 

percent Ta2O5). In postmagmatic albitites (formed by

albitization of pegmatites) minerals of the pyrochlore 

group with Ta2O5 reaching almost 9 percent, are formed.

The independent niobium minerals crystallize later 

than the titanium and zirconium minerals in both the 

nepheline syenite and postmagmatic formations and 

are commonly associated with processes of albHization 

and more rarely carbonatization.

Commercial concentrations of niobium occur in magmatic, pegmatitic, pneumatolytic, hydrothermal, and 

exogenic formations of nepheline syenites. Magmatic 

deposits are typical of agpaitic nepheline syenites, and 

pegmatitic and metasomatic deposits are associated with 

miaskitic syenites.

ALKALIC ULTRAMAFIC ROCKS

The geochemistry of niobium and tantalum in the 

alkalic ultramafic rocks of the Kola Peninsula was 

discussed at length by Kukharenko and others (1961, 

1965). Geological, petrological, and geochemical generalizations were made from data for at le^st nine 

alkalic ultramafic massifs of this region as studied by 

a number of Russian geologists. Represented are the 

Afrikanda, Kovdor, Vuori-Yarvi, Salmagorsk, Lesnaya 

Baraka, Lake Baraka, Tur'e Peninsula, Sallr,nlatvin, 

and Sebl'yavr massifs.

The most characteristic features of most of the massifs are the concentric arrangement of rock series and 

the constitution of individual intrusive bodies as multiple phases. Early phases of intrusions are injections 

of olivinites of different varieties including melilite- and 

perovskite-titanomagnetite-bearing types (Afrkanda).

A second intrusive phase in all the massifs h pyroxenite of different varieties. Some pyroxenites containing 

titanomagnetite and perovskite are coarse-grained and 

commonly constitute the core of the massifs. Finegrained pyroxenites, enriched in apatite and sphene, 

and to a certain extent enriched in nephel;ne and 

melanite, are associated with the border zone;? of the 

massifs. In some massifs the nepheline pyroxenites 

grade into jacupirangites (Afrikanda, Vuori-Yarvi). 

Pegmatites of diverse composition are associated with 

the pyroxenites.

A third intrusive phase consists of a series of melteigite-ijolite-urtite rocks accompanied by veins of 

ijolite pegmatite. These rocks commonly lie in the 

circumferential zone of the massifs.

As a result of postmagmatic alteration, ultramafic 

rocks and others have been changed in part to biotitephlogopite, apatite-forsterite-magnetite, and phlogopitecalcite-magnetite rocks, and carbonatites of diverse 

composition. Reaction between the alkalic ultramafic 

intrusives and the gneissic country rock has produced 

a contact aureole of fenites around the massifs.

The alkalic ultramafic rocks of the Kola Peninsula 

are anomalously high in both niobium and tantalum.
GEOCHEMICAL BEHAVIOR 23

The niobium content ranges from 134 to 518 ppm, and 

the tantalum content ranges from 13.2 to 59.6 ppm. 

The Nb:Ta ratio ranges from 8.7 to 10.2.

The geochemical behavior of niobium and tantalum 

was given in some detail by Kukharenko and associates 

from consideration of a large number of analyzed 

minerals from the alkalic ultramafic rocks and from 

the geologic succession of rock types. The character of 

the distribution of niobium and tantalum differs for 

different stages of formation of the massifs. In rocks of 

magmatic stages proper, these elements enter into 

titanium-bearing iron-magnesium silicates such as 

monoclinic pyroxenes, hornblendes, magnesium-iron 

micas, and titanomagnetites and especially into complex titanium oxide minerals such as perovskite and 

sphene and also into titaniferous garnet. In products of 

residual crystallization alkalic pegmatites and in 

some high-temperature autometasomatic products 

calcite-amphibole-diopside rocks (Afrikanda) not only 

is there some dispersal of niobium and tantalum in 

silicate and oxide minerals but some concentration in 

titanium and zirconium minerals such as dysanalyte 

and baddeleyite and in the independent niobiumtantalum minerals, ilmenorutile and pyrochlore. Higher 

concentrations of niobium and tantalum are characteristic of rocks of postmagmatic stages such as apatiteforsterite-magnetite and calcite-phlogopite-magnetite 

rocks and carbonatites, and minerals containing these 

elements are chiefly pyrochlore, zirkelite, baddeleyite, 

dysanalyte, and lueshite. Niobium and tantalum are 

apparently in part mobilized and reconcentrated in the 

process of postmagmatic alteration of pyroxenes and 

other minerals.

Kukharenko, Skrizhinskaya, Vainshtein, and Kakhama (1961) gave analyses for niobium and tantalum 

for 138 minerals from the alkalic ultramafic rocks of the 

Kola Peninsula. These analyses are grouped and 

summarized in table 23. From these data, these authors 

have concluded that a progressive increase in content 

of niobium and tantalum and a relative concentration 

of niobium with respect to tantalum occurs with the 

transition from pyroxenites to more alkalic rock types 

to pegmatites, or within different magmatic or postmagmatic phases. Such a general progression in concentration is shown well by monoclinic pyroxene, 

perovskite, titanomagnetite, sphene, pyrochlore, and 

others when considered as mineral groups related to 

the geologic succession of rock types for the Kola 

Peninsula as a whole. A similar progression is shown 

within the individual massifs such as Afrikanda. For 

example, concentrations of (Nb,Ta) 2O5 in the pyroxenes 

range from 0.005 percent in earlier formed rocks to 

0.0152 percent in later formed rocks of the Peninsula, 

and the ratio Nb2O5 :Ta2O5 ranges from 4 to 11. In

TABLE 23. Average contents of NbzO*, and TazOn and their ratios 

in some minerals of alkalic-ultramafic rocks of the Kola Peninsula, U.S.S.R.

[Kukharenko and others (1961, table 3, p. 184; 1965, table 172, p. 584-586)]

(Nb, Ta)2OB

No. Mineral Content

(in

percent)

1 Pyroxene from normal and ore pyroxenites. _________ . ___ 0. 005

2 Pyroxene from nepheline pyroxenites 

and ijolite-melteigites _______ _ .011

3 Pyroxene from alkalic pegmatites ___ .015

4 Pyroxene from fenites _____ _ ----- .004

5 Hornblende from metasomatic calciteamphibole-diopside rocks ______ . 014

6 Hornblende from alkalic pegmatites.... .008

7 Biotite from alkalic pegmatites and

ijolites--.-...-.. ..................... .0006

8 Phlogopite from alkalic pegmatites and

ijolites. ........................... .0005

9 Melanite from ijolite-melteigites and

their pegmatites. _________ .-. .020

10 Schorlomites from ore- and alkalicpegmatites ____________ __ .049

11 Sphene from pyroxenites ___ __ __ .24

12 Sphene from metasomatic calciteamphibole-diopside rock- __ ....... .946

13 Sphene from alkalic pegmatites _ __ . .61 

14 Titanomagnetites from olivinites ___ .0013

15 Titanomagnetites from alkalic pegmatites......... .......... _ . __ ... .0015

16 Perovskites from fine-grained olivinites- .55

17 Perovskites from pegmatitic olivinites . . 56 

18 Perovskites from ore pyroxenites __ .. .72

19 Perovskites from nepheline pyroxenites, melteigites, and ijolites __ . . _ 1. 05

20 Perovskites from metasomatic calciteamphibole-diopside rocks .. 1. 37

Of these, perovskite of first generation......... ..................... 1.29

Of these, perovskite of last generation _ ... _____ ...... _____ 1.45

21 Perovskite of alkalic pegmatites __ ... 1. 17

22 Baddeleyites from rocks of "ore complex" and carbonatites ____ .. .. 1.25

23 Zirkelites..... _ . ___ . _______ . 18.46

24 Pyrochlores of Vuori-Yarvi massif;

brown pyrochlores of first generation 

from rock of "ore complex" _ ... . 42.61

25 Pyrochlores of Vuori-Yarvi massif;

yellow pyrochlores from rocks of " ore

complex" (second generation) .. ... 56. 15

26 Pyrochlores of Vuori-Yarvi massif;

pyrochlore from carbonatized ore. ... 58. 13

27 Pyrochlores of Vuori-Yarvi massif;

pyrochlore from carbonatites __ 58. 54

28 Pyrochlores of Vuori-Yarvi massif;

hatchettolite from fenites.. . 51. 64

29 Pyrochlores of Kovdorsk massif;

brown pyrochlores from rock of

"ore complex" _______ .... ... 48.0

30 Pyrochlore from carbonatite, early

generation........ _ ..... ... 53.18

31 Pyrochlore from carbonatite, late

generation.... ________ .... . 64.23

32 Pyrochlore of Sebl'vavr massif; from

calcite carbonatite (early generation) . 62. 69

33 Pyrochlore of Sebl'yavr massif; pyrochlore from dolomitic carbonatite

(later generation) . __ __ .... ___ . 66.16

34 Lueshite. ........................... 65.75

35 Natroniobite.. ...--.----.--....-...- 74.89

Number

of samples

13

7

2

1

1

2

2

2

3

4

3

5

6 

3

2

17

5 

10

4

5

1

1

18

8

8

1

4

1

2

1

1

1

1

1

1

1

1

NbaOs

Ratio

4.0

11

9

20

35

15

;=4~5

=4-5

7

13

16.5

13

25 

5

8

9

13 

10

14

16

9

28

17

3

12.3

8

39

30

51

4.8

7

6.7

28

10.7

38 =115

90

:TaaCNnnber

ofsairioles

12

7

2

1

1

2

2

2

3

4

2

2

3 

3

2

14

5

7

4

4

1

1

10

8

7

1

4

1

2

2

1

1

4

1

3

2

2

the Afrikanda massif the Nb2O5 :Ta2O5 ratios in 

pyroxenes range from 2 to 3 in the earlier coarsegrained pyroxenite in the inner parts of the massif to 

2-5 in the fine-grained pyroxenite to 5-25 in the later 

nepheline pyroxenite in the peripheral zone.

Pyrochlore in the alkalic ultramafic rocks is characterized by the greatest variation in the ratio Nb2O5 : 

Ta2O5 . Early generations of pyrochlore commonly are 

enriched in tantalum and uranium, approximating 

hatchettolite in composition and having ratios in the 

range 7-11. Second-generation pyrochlore from the same 

rocks have ratios 30-51. Maximum ratios reaching 53
24 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

are found in pyrochlore from the youngest dolomite 

carbonatite.

The same trend, niobium concentrating progressively 

with respect to tantalum, is shown clearly by paragenetic mineral series, both in different rock types and 

different massifs. Ratios of Nb2O5 :Ta_O5 ir» paragenetically related minerals are given in table 24. In all 

the series given (with a single exception that Kukharenko 

suspects is an analytical error) representing olivinites, 

ore pegmatites, carbonatites, and ore complexes of 

several massifs a progressive increase in the ratio is 

shown.

In summary, in the beginning stages of massif formation of alkalic ultramafic rocks, niobium and tantalum 

do not form independent minerals but are camouflaged 

principally by titanium in rock-forming pyroxenes and 

titanium oxide minerals. The first fractions of crystallizing rock are relatively deficient in niobium or relatively enriched in tantalum. Later precipitates in each 

series of rocks are enriched in niobium. In differentiated 

intrusives, the relative concentration of niobium increases in the late alkali-enriched outer zones of the 

massifs. In products of residual crystallization, niobium 

and tantalum form independent minerals such as pyrochlore, or they enter into complex titanium or zirconium 

minerals. Generally, rock-forming silicates and oxides 

of residual origin are enriched in both niobium and tantalum but more highly enriched in niobium. In postmagmatic phases of alkalic ultramafic rocks such as 

carbonatites, local increases of niobium and tantalum in 

independent minerals and complex oxides of titanium 

and zirconium are also characteristic, niobium being

TABLE 24. Ratios of NbnOs'. Ta2 05 in minerals grouped according 

to their paragenetic association, Kola Peninsula, U.S.S.R.

[Kukharenko and others (1961, table 4; 1965, table 173, p. 590)]

Mineral Locality and rock

Number of 

NbsOsrTajOs samples

Titanomagnetite____ Afrikanda; olivinites_ 

Perovskite. ____ __ _ _do ________ _ 

Titanomagnetite _ _ Afrikanda; ore

pegmatite. 

Perovskite. ________ ____do____________

Baddeleyite__ ______ Vuori-Yarvi; rocks

of ore complex. 

Zirkelite _ _-.____. ____do__ ____ ___

Pyrochlore__ _______ ____do_____________

Zirkelite- _. ____ _. Sebl'yavr;

carbonatites. 

Pyrochlore____-____ ____do____ _ _____

Baddeleyite ________ Lake Varaka ;

carbonatites 

Pyrochlore__ _______ ____do____________

Baddeleyite________ Kovdor massif;

rocks of ore

complex.

Pyrochlore___ ______ __ _do

5. 0

12

8

17

3

16.5

26. 5

7. 6

24

4. 6

8. 2 

3

10.5 ' 7

3

19

2

10

2

3

2

2

»Suggested correct value (Kukharenko and others, 1961) =25.

relatively enriched as compared with tantalum. Niobium and tantalum are reconcentrated, in part at least, 

as a result of alteration of earlier formed primary rockforming silicates.

VOLCANIC ROCK SERIES

David Gottfried (written commun., 1965), in studying the niobium content in suites of volcanic rocks, 

distinguished three fairly distinct trends of variation of 

niobium during magmatic differentiation. Niobium increases throughout differentiation as shown in the 

alkalic and alkali-calcic volcanic suites from Augusta 

County, Va., and the Big Bend area, Texas. Niobium 

decreases throughout differentiation as shown by series 

members in the high calcic suites from Saipan; Mount 

Garibaldi, British Columbia; and Strawberry Mountains, Oreg. Niobium increases slightly or remains 

nearly constant in calc-alkalic rocks from Medicine 

Lake Highland, Calif. The study of these suites suggests that the variation during magmatic differentiation 

of niobium, and probably tantalum, is more complex 

than generally assumed when examined on the basis of 

more detailed petrographic classification. Most of the 

literature treats the subject on the basis of ver^ generalized classification, and, as a result, some complex 

variations are concealed by more dominant trends.

SEDIMENTARY BOCKS

Data on the niobium and tantalum content of 

sedimentary rocks are summarized in table 13. They 

indicate that niobium and tantalum dissolved during 

the weathering cycle tend to be concentrated in the 

hydrolyzates clays, laterites, and bauxites. An appreciable amount of niobium, however, evidently escapes 

precipitation and reaches the ocean where it precipitates 

with the clays and especially with the manganese 

oxide nodules. Two such nodules analyzed by Rankama 

(1944, 1948) contain 147 and 35 ppm niobium and less 

than 1.6 and less than 0.7 ppm tantalum. A nodule 

from the Indian Ocean analyzed by Pachadzhanov, 

Bandurkin, Migdisov, and Girin (1963) contains 7.6 

ppm niobium and 2.3 ppm tantalum (Nb:Ta=3.3) 

in its core and 29 ppm niobium and 0.17 ppm tantalum 

(Nb:Ta=170) in its outer shell. The core in such 

nodules is considered to represent altered submarine 

volcanic material, whereas the outer shell is a product 

of deep-sea deposition. A strong relative enrollment 

in niobium with respect to tantalum is shown between 

core and shell, and the decrease in the tantalum content 

of the shell reflects the low abundance of tantalum in 

the deep-sea environment and is an indication of the 

geochemical separation of tantalum and niobium in 

this environment.

Pachadzhanov (1963) recently investigated the 

distribution of niobium and tantalum in clays of the
GEOCHEMICAL BEHAVIOR 25

Russian Platform and has pointed out some interesting 

facts bearing on the geochemical behavior of these 

elements in sedimentary processes. In that report, 

clays formed in humid environments are distinguished 

from those formed in arid environments. The average 

niobium and tantalum contents for the humid clays 

are 20.1 and 2.4 ppm respectively, and the Nb:Ta ratio 

is 8.4. The same averages for arid clays are 13.3 and 0.9 

ppm respectively, and the Nb:Ta ratio is 14.8. The 

averages of all clays investigated are 18.3 and 2, close 

to the clarkes of these elements. Higher concentrations 

of both niobium and tantalum occur in the humid 

environment clays and are ascribed to residual concentration resulting from the removal by leaching of 

ions potassium, sodium, calcium, magnesium, silicon, 

and others. The Nb:Ta ratio is higher in the aridenvironment clays because niobium appears to be more 

mobile and somewhat more easily removed than tantalum in the humid environment. The greater mobility 

of niobium and partial fractionation of niobium from 

tantalum are shown by a progressive decrease in the 

Nb:Ta ratio from the provenance area to the basin 

of marine deposition. Possible explanations offered 

for the fractionation are differences in solubility and 

stability of organic niobium and organic tantalum 

compounds that may be formed in weathering, or 

differences in the behavior of niobium and tantalum 

in solution with such elements as titanium, zirconium, 

and thorium, which may have chemical influence on 

them.

The content of niobium and tantalum in sediments 

evidently reflects to a considerable degree their content 

in the source rocks. A kaolinite formed from Nigerian 

columbite-bearing granites contained 478 ppm niobium 

and 82 ppm tantalum. This was not included in the 

samples averaged in table 13. The data on bauxites 

also illustrate the important nature of the source rock 

bauxites from alkalic rocks containing twelve times as 

much niobium as those derived from other types of 

rocks. This is further verified by Fleischer, Murata, 

Fletcher, and Narten (1952) who found less than 100 

ppm in each of 37 bauxitic rocks derived from sources 

other than alkalic rocks. The figures given by Pearson 

(1955) on Gold Coast bauxite (20 ppm niobium) derived from gneisses and on bauxite from Nyasaland 

(500 ppm niobium) derived from alkalic rocks agree 

with this.

Bauxites are commonly enriched in niobium and 

tantalum, however, as compared with their source 

rocks, and most bauxites contain concentrations of 

these elements that exceed their clarkes. Gordon and 

Murata (1952) showed that Arkansas bauxite derived 

from nepheline syenite is characterized by a 3.8-fold 

enrichment of niobium.

According to Pachadzhanov (1964) niobium and 

tantalum are present in the bauxite chiefly in th^ aluminum minerals, gibbsite, boehmite, and diaspore, and, 

to a lesser extent, in titanium and zirconium mir^rals. 

Fleischer, Murata, Fletcher, and Narten (1952), however, found that the niobium in tne Arkansas bauxite 

is concentrated in ilmenite.

DEPOSITS OF NIOBIUM AND TANTALUM

Concentration or enrichment of niobium and tantalum is characteristic in several magmatic and postmagmatic stages involved in the emplacement and 

consolidation of various types of igneous rocks; additionally, some concentration, independent of the origin 

of the rocks, can be produced as a result of excsjenic 

processes. Most examples of such concentration are of 

small magnitude and are of geochemical interest only; 

however, some concentration is of a magnitude large 

enough to be considered in the realm of commercial 

deposits.

Deposits of these elements are grouped in tat T e 25 

both according to the type of rocks or magma series 

in which they occur or to which they are genetically 

related and according to the geologic process by which 

they were formed. This scheme of classificatior was 

used by Kuz'menko (1959, 1960), but it is sornowhat 

modified here to include more examples of North 

American deposits. It is beyond the scope of this paper 

to describe tne individual niobium and tantalum deposits and their geology. Some of them have been 

mentioned in other parts of this text in connection with 

geochemical subjects. The classification tabta of 

Kuz'menko will serve to place the different deposits 

and examples in the proper genetic perspective. Most 

occurrences of niobium and tantalum can be conveniently classed using this scheme.

The commercial recovery of niobium is made at 

present from columbite-tantalite, pyrochlore, and 

euxenite ores and possibly from rocks containing 

loparite and nmrmanite. The recovery of tantalum is 

(or has been) chiefly from columbite-tantalite, microlite, and euxenite ores. Large commercial deposits of 

columbite-tantalite occur in biotite granites (magmatic 

type) of Nigeria, as well as in placers (exogenic type) 

derived from such rocks and pegmatites. Colurrbitetantalite with high tenor of tantalum from pegmatites 

(pegmatitic type) of the Congo region, Africa, and 

Brazil is the world's principal source of tantrlum. 

Deposits of microlite from lithium-rich pegmatites 

(pegmatitic type) constitute small but significant 

sources of tantalum in the Taos region, New Mexico. 

Placers (exogenic type) containing euxenite and other 

minor pegmatite minerals have been a commercial 

source of both niobium and tantalum at Bear Valley,
26 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

TABLE 25. Classification of deposits of niobium and tantalum

[After Kuz'menko (1959)1

Process Granites Alkalic granites Nepheline and alkalic syenites Alkalic ultramafic rocks

Magmatic.

PegmatiticPneumatolytichydrothermal.

Contact-metasomatic. 

Magmatic(?)-

rnetasornatic (?). 

Exogenic..-------

Biotite granites with columbite (Jos 

Plateau, Nigeria).

Granites with euxenite, fergusonite 

(Idaho batholith, Idaho).

Simple pegmatites with columbite 

tantalite.

Complexly zoned and replaced pegmatites with lithium minerals, 

tantalite, microlite, etc. (Harding 

pegmatite, New Mexico).

Feldspar-quartz veins...............

Greisen veins.

Alkalic granites with riebeckitc and 

pyrochlore (Nigeria; Mount Rosa, 

Colo.).

Agpaites-urtites, lujavrite, juvites 

with loparite (Lovozero massif, 

U.S.S.R.). 

Miaskites with pyrochlore (Vishnevye Mountains, U.S.S.R.).

Pegmatites with columbite-tantalite, Nepheline syenite, pegmatites (Urals 

pyrochlore, astrophyllite, etc. and Kola Peninsula). 

(Mount Rosa, Colo.)

Pyroxenites and olivinite? with perovskite (Afrikanda massif, 

U.S.S.R.).

Rutile-brookite pegmatite," (Magnet 

Cove, Ark.).

Albitized zones. 

Greisen zones..

Feldspar-quartz veins............... Albitites with pyrochlore__,...--. Feldspar-calcite veins (Magnet Cove,

Ark.)

-. __._....__................. Biotite-calcite veins with pyrochlore. Carbonatites with knopite (Magnet

Cove, Ark.).

Albitized zones...-----.--.------______...._____._____. Carbonatites with pyrochlore and

hatchettolite (Sukulu, Uganda).

-----------------------._-.._.--.-_.-. Albitized zones with pyrochlore-.--- Natrolite-biotite zones in ijolite with

knopite (Oka, Quebec).

-------------------------------------- Carbonatized zones with pyrochlore. Carbonatized zones with pyrochlore.

-----.-------.-.--------__--_--.--.--- Albitized, nephelinized zones with perovskite, pyrochlore at contact of

alkalic rocks and Carbonatites (Oka, Quebec).

-------------------- -_-..-......-.. . Large stocklike carbonatite masses with pyrochlore (Iron Hill, Cclo.).

Cassiterite, columbite-tantalite placers (Nigeria) ..........................^ Zircon, pyrochlore placers (Sukulu, Uganda).

Samarskite placers (Altai, U.S.S.R.)..----_-_.--_-__.__.-_. ..__....- Ilmenite-rutile placers (Urals).

ILmeniteplacers (Ukraine)..-------- ...............................__ Bauxites (Arkansas).

Euxenite placers (Bear Valley, Idaho).--..__.___.____.__._.___.__..__._-__

Idaho. Large, low-grade deposits of pyrochlore, probably 

the chief future source of niobium, occur in Carbonatites 

and related alkalic rocks (classed variously from magmatic to pneumatolytic types) from complexes in 

Brazil, southeastern Canada, Norway, Germany, central Africa, Russia, and the United States (Pecora, 

1956). Deposits of loparite and murmanite apparently 

have been mined in the agpaitic nepheline syenites 

and other alkalic rocks (magmatic types) of the Lovozero massif, Kola Peninsula, U.S.S.R. Although 

extraction has never been feasible economically, 

because of the low tenor of niobium, large quantities 

of the element are present in the bauxite deposits 

(exogenic type) of Aikansas and remain an untapped 

source. Similarly, certain riebeckite granites of Nigeria 

(magmatic type) contain sufficient disseminated pyrochlore to be considered another large potential source.

SUGGESTIONS FOR FUTURE WORK

Significant future advances in the field of niobiumtantalum geochemistry will depend largely on the 

availability of a large number of additional accurate 

chemical analyses of different types of rocks and 

minerals so that the abundances of these elements 

and their ratios can be more accurately established. 

Such data are fundamental to any understanding of 

geochemical processes and are necessary to deciphering 

the geochemical characteristics of these elements in 

different geologic environments.

Special attention should be given to the classification 

of rocks and to the selection of representative samples 

of rocks to be analyzed. If possible, rocks selected for 

niobium-tantalum analyses should also be analyzed

chemically for major constituents, allowing more precise classification or allowing comparison on the basis 

of differentiation index or other groupings.

Representative sampling at the outcrop will remain 

the responsibility of the collector; however, the selection of sufficient samples to represent the worldwide 

occurrences reasonably and practically should be the 

goal. At the present time certain types of rooks are 

more abundantly represented than others, and certain 

regions are more extensively represented, so that considerable regional bias and petrologic bias exist.

The study of the distribution of these elements in 

comagmatic series or their distribution in related rocks 

of individual complexes or massifis can lead to a clearer 

understanding of the behavior of these elements in magmatic processes as well as demonstrate variations and 

peculiarities in concentration of these elements from 

complex to complex and region to region. Some studies 

of this type have been made in both the U.S.S.R. and 

the United States, but few have been made ir which 

accurate analysis of both niobium and tantalum were 

available.

The available data on niobium and tantalum contents 

of sedimentary rocks are very scanty and do not 

permit evaluation of the fate of these elements in the 

weathering cycle. Study of the contents of these e^ments 

in series of samples from fresh rocks of various types of 

soils is badly needed.

Also highly desirable are additional detailed studies 

of the distribution of these elements among the major 

rock-forming minerals of various rock types. The 

available data have been discussed above, but there is 

evidence that there are large gaps in our knowledge.
SUGGESTIONS FOE FUTURE WORK 27

More investigation is needed on the chemical behavior 

of these elements in compounds and minerals and on 

their mobility and solubility in ionic complexes in 

different media.

Increased knowledge of the geochemistry of niobium 

and tantalum can lead to a better understanding of the 

origin of these elements in rocks, minerals, and ores. 

Questions on niobium and tantalum remaining to be answered are:

1. Are some of the rocks anomalously high in niobium 

and tantalum derived from the mantle?

2. Has there been fractionation of these elements, relatively or absolutely, by magmatic processes 

during emplacement of rocks possibly originating 

in the mantle?

3. Are these elements present at clarke values in most 

crustal magmas, and are they concentrated or 

fractionated only in late magmatic and certain 

postmagmatic plutonic stages?

4. Are certain concentrations of these elements characteristic of certain magma types?

5. Are there relations between concentration of these 

elements in rocks and in ore deposits of these 

elements, and are there any proximal relations 

between ore deposits and the distribution of niobium and tantalum in the host rocks?

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kimberlites: Akad. Nauk SSSR Sibirskoye Otdele.niye, Inst. 

Geokhim. Trudy, p. 142-146 (in Russian).

Kukharenko, A. A., Orlova, M. P., Bulakh, A. G., B".gdasarov, 

E. A., Rimskaya-Korsakova, O. M., Nevedov, E. I., 

Il'inskii, G. A., Sergeev, A. S., and Abakumo^a, N. B.,

1965. Caledonian complex of ultrabasic, alkalic rocks and 

carbonatites of the Kola Peninsula and Northern Karelia 

(Geology, petrology, mineralogy, geochemistry): Moscow, 

Izdatel'stvo "Nedra," 1965, 772 p.
REFERENCES, EXCLUSIVE OF GLOSSARY 29

Kukharenko, A. A., Skrizhinskaya, V. I., Vainshtein, E. E., and 

Kakhana, M. M., 1961, The geochemistry of niobium and 

tantalum in complexes of alkalic-ultrabasic rocks: Vses. 

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Kuz'menko, M. V., 1959, The geochemistry of tantalum and 

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i Kristallokhim. Redkikh Elementov Trudy, v. 3, p. 3-25 

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 1960, Genetic types of deposits and ore manifestations 

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Davey and Co., 1966.

Mackin, J. H., and Schmidt, D. L., 1956, Uranium- and thoriumbearing minerals in placer deposits in Idaho, p. 375-380, 

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p. 17-34.

Mason, B. H., 1958, Principles of geochemistry, 2d ed.: New 

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Montgomery, Arthur, 1950, Geochemistry of tantalum in the 

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Morris, D. F. C., and Olya, A., 1960, The determination of 

tantalum in rocks by neutron activation analysis: Talanta, 

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Moshier, R. W., 1964, Analytical chemistry of niobium and 

tantalum: New York, Macmillan Co., 278 p.

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in museovites from pegmatites of the Dzirulsk crystalline 

massif: Geokhimiya 1958, no. 4, p. 380-383 (in Russian); 

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Pachadzhanov, D. N., 1963, Geochemistry of niobium and 

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(in Russian); translation in Geochemistry 1963, no. 10, 

p. 963-976.

 1964, Geochemical relation of tantalum, niobium, and 

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(in Russian); translation in Geochemistry International 

1964, no. 5, p. 889-896.

Pachadzhanov, D. N., Bandurkin, G. A., Migdisov, A. A., and 

Girin, Yu. P., 1963, Data on the geochemistry of manganese 

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Page, L. R., and others, 1953, Pegmatite investigations 1942- 

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 1955b, The principles governing trace element behavior 

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Rudovskaya, L. N., 1964, Geochemistry of granite pegmatites 

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Sitnin, A. A., and Bykova, A. V., 1962, The first specimen of 

microlite from granite: Akad. Nauk SSSR Dioklady, v. 

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141-144.

Sitnin, A. A., and Razina, I. S., 1963, Chemical compositior of 

lithium micas from metasomatieally altered granites: Geohimiya 1963, no. 7, p. 724-728 (in Russian); translation in 

Geochemistry 1963, no. 7, p. 724-728.

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Geochemistry International 1964, no. 2, p. 221-228.

Staatz, M. H., and Trites, A. F., 1955, Geology of the Quartz 

Creek pegmatite district, Gunmson County, Colorado: U.S. 

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Sutherland, D. S., 1965, Potash-trachytes and ultra-potassic 

rocks associated with the carbonatite complex of the Toror 

Hills, Uganda: Mineralog. Mag., v. 35, p. 363-378.
30 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

Taylor, S. R., 1964, Abundance of chemical elements in the 

continental crust A new table: Geochim. et Cosmochim. 

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1243-1261.

Temple, A. K., and Grogan, R. M., 1965, Carbonatite and related alkalic rocks at Powderhorn, Colorado: Econ. Geology, 

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elements in some major units of the earth's crust: Geol. Soc. 

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islands, South Greenland: pt. Ill, Olivine gabbros, syenogabbros, and anorthosites, and pt. IV, The nepheline 

syenites of the Hviddal composite dyke: Medd. om Gr0nland, v. 169, no. 3, 80 p.

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Vinogradov, A. P., 1962, Average content of chemical elements 

in the principal types of igneous rocks of the earth's crust: 

Geokhimiya 1962, no. 7, p. 555-571 (in Russian); translation in Geochemistry 1962, no. 7, p. 641-664.

Voloshin, A. V., and Miletskii, B. E., 1966, Some peculiarities 

of niobium behavior in the process of sodium metasomatism: Geokhimiya 1966, no. 4, p. 470-473 (in abstract in 

Geochemistry International 1966, no. 2, p. 360.

Wambeke, L. van, Brinck, J. W., Deutzmann, W., Gonfiantini, 

R., Hubaux, A., Metais, D., Omenetto, P., Tongiorgi, E., 

Verfaillie, G., Weber, K., and Wimmenauer, W., 1964, Les 

roches alcalines et les carbonatites du Kaiserstuhl: European Atomic Energy Community Euratom, EUR 1827, 

d, f, e, 231 p.

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naturally occurring isotope of tantalum: Phys. Rev., v. 97, 

p. 566-567.

Znamenskii, E. B., 1957, On the average contents of niobium 

and tantalum in igneous rocks and the crust of the earth: 

Geokhimiya 1957, no. 8, p. 730-734 (in Russian); translation in Geochemistry 1957, no. 8, p. 855-860.

 1964, The average contents of niobium and tantalum in 

granitic rocks: Akad. Nauk SSSR Geokhim. Konf. "Khimiya Zemnoi Kory" Trudy, v. 2, p. 301-316 (in Russian).

Znamenskii, E. B., Konysova, V. V., Krinberg, I. A., Popolitov, 

E. I., Flerova, K. V., and Tsykhanskii, V. D., 1962, Distribution of titanium, niobium, and tantalum in sphenecontaining granitoids: Geokhimiya 1962, no. 9, p. 800-805 

(in Russian); translation in Geochemistry 1962, no. 9, p. 

919-925.

Znamenskii, E. B., Krinberg, I. A., Popolitov, E. I., and Flerova, 

K. V., 1962, Abundance of niobium in granitic rocks of the 

basin of the Little White River in Eastern Sayan: Akad. 

Nauk Zapiski Vostoch.-Sibirsk. Otdel. Vses. Mineral. 

Obshch., no. 4, p. 69-77 (in Russian).

Znamenskii, E. B., Nesterenko, G. V., Tsykhanskii, V. D., and 

Konysova, V. V., 1965, Abundance of niobium and tantalum in traps, in Problemy Geokhimii (Vinogradov volume): 

Akad Nauk SSSR Inst. Geokhimii i Anal. Khimii, p. 410- 

417.

Znamenskii, E. B., and Popolitov, E. I., 1964, Dependence of 

the geochemical behavior of niobium and tantalum on the 

paragenesis of titanium and titanium containing minerals

in granitic rocks: Akad. Nauk SSSR Siberskoye Otdeleniye, 

Geokhim. Redkikh Elementov., p. 57-62 (in Russian). 

Znamenskii, E. B., Rodionova, L. M., and Kakhana, M. M., 

1957, Distribution of niobium and tantalum in granites: 

Geokhimiya 1957, no. 3, p. 226-232 (in Russian); translation in Geochemistry 1957, no. 3, p. 267-270.

GLOSSARY OF NIOBIUM AND TANTALUM MINERALS

A glossary of niobium and tantalum minerals is 

presented on the following pages as well as lists of 

minerals of other elements that contain niobium and 

tantalum in minor amounts. The chief purpose of 

these data is to show the relationships among the 

various series of minerals and to give the most recent 

information on synonomy among the mineral^. Some 

of the names included in the glossary have b°-en disapproved or discredited by the Commission on New 

Minerals and Mineral Names of the International 

Mineralogical Association. Although no indication 

has been made as to the present validity of thes^ names 

as considered by the Commission, their presentation 

here is not meant to endorse their usage, but only to 

show the synonomy and to give reference to the original 

usage of the name, where possible.

Minerals that contain niobium and tantalum are 

chiefly oxides and multiple oxides, hydroxides, and 

silicates; one borate is known. About 90 species and 

varieties of these minerals contain niobium and tantalum as major constituents and can be considered 

niobium-tantalum minerals proper. A cons: derable 

number of minerals of other elements contain minor or 

trace amounts of niobium and tantalum. Complex 

ionic substitution in the various multiple-oxide minerals 

makes it difficult to represent them by simple chemical 

formulas. By convention, the minerals are represented 

by general formulas expressed in terms of three basic 

components, A, B, and X. (Palache and others, 1944; 

Bokii, 1956; Kuz' menko, 1959; Veen, 1963). Elements 

with ionic radii greater than 0.80 A and which normally 

occur in minerals in eight-fold (rarely six-fold) coordination or higher are designated by A. Elements 

having ionic radii in the range 0.57-0.80 A (such as 

niobium, tantalum, and titanium) and occulting in 

six-fold coordination are represented by E. Nonmetallic elements, oxygen, fluorine, chlorir^, and 

hydroxyl ion are designated X. Silicates and phosphatebearing minerals are expressed using the A, B, and X 

designations in conjunction with appropriate siliconoxygen and phosphorus-oxygen combinations.

The glossary consists of four parts: I, a classification 

of the niobium-tantalum mineral series according to 

chemical types designated in terms of A, B, and X; 

II, an alphabetical listing of niobium-tantalum minerals giving their formulas and brief notations on their 

crystal system, composition, mode of occurrence,
GLOSSARY CHEMICAL CLASSIFICATION OF MINERALS OF NIOBIUM AND TANTALUM 31

synonomy where appropriate, and pertinent references; 

III, an alphabetical listing of minerals and their 

chemical formulas in which 1-5 percent niobiumtantalum have been reported; and IV, an alphabetical 

listing of minerals and their chemical formulas in which 

less than one percent niobium-tantalum have been 

detected. The latter, list IV, is not meant to be complete, 

inasmuch as a systematic search of the literature for 

trace amounts of niobium-tantalum in minerals has 

not been made.

It is beyond the scope of this report to describe these 

minerals or to include determinative tables. The 

reader can obtain more detailed mineralogic data by 

consulting the references cited in the glossary. Supplemental information may be obtained from Dana's 

System of Mineralogy, 6th and 7th editions, and the 

"Chemical Index of Minerals" (Hey 1955, 1963). 

In the glossary Palache, Berman, and Frondel (1944) is 

entitled "Dana VII."

PART I. CLASSIFICATION OP MINERALS OP NIOBIUM 

AND TANTALUM ACCORDING TO CHEMICAL TYPES

OXIDES, HYDKOXIDES, AND MULTIPLE OXIDES

Ilmenorutile-striiverite series, 6X2, B2Xt 

Ilmenorutile (Ti,Nb,Ta,Fe) 2O4 

Striiverite (Ti,Ta,Nb,Fe) 2 04 

Tapiolite-mossite series, BB^Xt 

Tapiolite (Fe,Mn)(Ta,Nb) 2O6 

Mossite (Fe,Mn)(Nb,Ta) 2O6 

Perovskite series ABX$

Dysanalyte (Ca,Ce,Na) (Ti,Nb,Ta)O3 

Latrappite (Ca,Na)(Nb,Ti,Fe)O3 

Loparite (Na, Ce, Ca) (Ti, Nb) O3

Metaloparite=hydrated loparite

Nioboloparite=niobian loparite

Irinite=thorian loparite 

Lueshite NaNbO3

Natroniobite NaNbO3 or NaNb2O5OH 

Fergusonite-formanite series ABXi

Fergusonite (Y, Er, Ce, Fe) (Nb, Ta, Ti) O4

Risorite (Y,Er,Ce,Fe) (Nb,Ti,Ta)O4 

Beta-fergusonite=polymorph of fergusonite 

Formanite (Y,Er,U,Th,Ca) (Ta,Nb,Ti)O4 

Stibiotantalite-stibiocolumbite series, ABXi 

Stibiotantalite Sb(Ta,Nb)O4

Stibiobismutotantalite=bismuthian Stibiotantalite 

Stibiocolumbite Sb(Nb,Ta)O4 

Bismutotantalite Bi(Ta,Nb)O4 

Columbite-tantalite series, AB2Xs 

Columbite (Fe,Mn)(Nb,Ta) 2O6

Ferrocolumbite (Fe,Mn)(Nb,Ta) 2O6

Manganocolumbite (Mn,Fe) (Nb,Ta)sOfl 

Magnocolumbite (Mg,Fe)(Nb,Ta) 2O8 

Tantalite (Fe,Mn)(Ta,Nb) 2Oft

Ferrotantalite (Fe,Mn)(Ta,Nb) 2O8

Manganotantalite (Mn,Fe) (Ta,Nb) 2Os 

Ixiolite (Ta,Fe,Sn,Nb,Mn) 4Og 

Wodginite (Ta,Sn,Mn,Nb,Fe,Ti) 1(1O32

Olovotantalite=Sn-Ma tantalate=wodginite?

Euxenite-poly erase series, AB2Xt

Euxenite ( Y, Ca, Ce, U, Th) (Nb,Ti, Ta) 2O6 

Tanteuxenite ( Y, Ca, Ce, U, Th) (Ta, Ti, Nb) 2O6 

Polycrase ( Y,Ca,Ce,U,Th) (Ti,Nb,Ta) 2O6 

Tantpolycrase ( Y,Ca, Ce, U,Th) (Ti,Ta,Nb) 2O6 

Kobeite ( Y,Fe,U) (Ti,Nb,Ta) 2 (O,OH) 6 

Fersmite (Ca,Ce)(Nb,Ti) 2 (O,F) 6 

Aeschynite-priorite series ABZX^

Aeschynite (Ce,Ca,Fe,Th) (Ti,Nb) 2 06

Sinicite (Ce,Nd,Th,U)(Ti,Nb) 2 06

Niobo-aeschynite (Ce,Ca,Th) (Nb,Ti) 2O»

Lyndochite = niobian-thorian aeschy nite (?) 

Polymignyte (Ca,Fe,Ce) (Zr,Ti,Nb,Ta) 2 06 

Priorite (Y,Er,Ca,U,Th)(Ti,Nb) 2O6 

Pyrochlore-betafite-microlite series Az-xBzXi

Pyrochlore (Na,Ca,Ce) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7

Koppite=cerian-ferrian pyrochlore

Marignacite (Ce,Ca,Na) 2 (Nb,Ti,Ta)2 (O,OH,F) 7 

Niobozirconolite CaZr(Ti,Nb) 2O7 

Obruchevite (Y,U,Ca) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7 

Pandaite(Ba,Sr) 2 (Nb,Ti,Ta) 2 (0,OH,F) 7

Priazovite= uranian-yttrian pyrochlore 

Scheteligite= Mn, Y,Sb,Ti-pyrochlore 

Yttrobetafite= intermediate between obruchevite and

pyrochlore

Yttrohatchettolite (Ca, Y, U) 2 (Nb,Ta,Ti) 2 (O,OH.F) 7 

Betafite(U,Ca) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7

Hatchettolite (Ca,U) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7

Rare-earth betafite (RE,U,Ca) 2 (Nb,Ti,Ta) 2 (O,OH.F) 7

Samiresite (U,Pb) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7

Titanobetafite (U,Ca) 2 (Ti,Nb,Ta) 2 (O,OH,F) 7

Zirconium betafite (U,Ca) 2 (Ti,Nb,Zr) 2 (O,OH,F) 7 

Microlite (Ca,Na) 2 (Ta,Nb,Ti) 2 (O,OH,F) 7

Bismutomicrolite= bismuthian microlite

D jalmaite = microlite

Plumbomicrolite (Pb,Ca) (Ta,Nb) 2 (O,OH,F)r 

Rijkeboerite (Ba,Fe,Pb,U) (Ta,Nb,Ti,Sn) 2 (O,OH,H2O) 7 

Westgrenite (Bi,Ca)(Ta,Nb) 2O6 (OH) 

Samarskite series AB2Xt

Samarskite ( Y,Fe,U) (Nb,Ti,Ta) 2 (O,OH) 6

Calciosamarskite= calcian samarskite

Vietinghofite (Fe, U, Y) (Nb,Ti,Ta) 2O6 

Khlopinite (Fe,Y,U) 2 (Ti,Nb,Ta) 2O6 

Ishikawaite (U,Fe, Y) (Nb,Ta,Ti) 2O6

Plumboniobite (Ca,Pb,Fe,Y,U)Nb2O» 

Yttrotantalite (Y,Fe)(Nb,Ta)O4 (approximately) 

Hjelmite= doubtful Mn-Ca yttrotantalite 

Other tantaloniobates

Thoreaulite Sn(Ta,Nb) 2O7 

Pisekite= complex multiple oxide 

BelyankiniteCa(Ti,Zr,Si,Nb)A3-14H2O 

Gerasimovskite (MnCa)2 (Nb,Ti) 5O12 -9H2O 

Sunpsonite Al4 (Ta,Nb) 3 (O,OH,F) 14

SILICATES

Nenadkevichite (Na,Ca) (Nb,Ti) (Si2O7) -2H2O 

Niobolabuntsovite (Ca,Ba) (Ti,Nb) (Si2Or) -2H2O 

Shcherbakovite (K,Na,Ba) 3 (Ti,Nb) 2 (Si2O7) 2 

Wohlerite NaCa2 (Zr,Nb) (Si2O7 )(O,F)

Karaasurtite(Ce,La,Th) (Ti,Nb) (Al,Fe) ( SiP) 2O7 (OH) 4-3HsO 

Type AiB Si2OioX"

Niocalite Ca4NbSi2O10 (OH,F)
32 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

Type ?vl 2 £2Si2O9 (n-:r)Na3PO4 -zH2O

Lomonosovite Na2 (Ti,Nb) 2Si2O9 -Na3PO4

Beta-1 omonosovite = hydrous variety of lomonosovite

Murmanite Na2 (Ti,Nb) 2Si2O9-nH2O

Betamurmanite= weathered betalomonosovite

Epistolite (Na,Ca) 2 _I(Nb,Ti) 2Si2O9 -:c (OH) I./i(H2O,Na3PO4) 

Type A2B SiO5X

Fersmanite (Ca,Na) 2 (Ti,Nb)(SiO5 )(F,OH) 

Type.44 £8 (Si4 012)X17

Baotite Ba4 (Ti,Nb) 8 (Si4Oi2)ClO16 

Others

Niobophyllite (K,Na) 3 (FeMn) 6 (Nb,Ti) 2 (Si,Al) 8 (O,OH,F) 31

Ilimaussite Na4Ba2CeFeNb2Si 8O28 -5H2O

BORATE

Behierite (Ta,Nb)BO4

PABT II NIOBIUM AND TANTALUM MINEBALS

AESCHYNITE (also eschynite)

(Ce,Ca,Fe,Th)(Ti,Nb) 2 O6

Orthorhombic, naturally metamict.

Cerium-dominant part of the aeschynite-priorite series.

(Nb,Ta) 2O5= 30-33 percent.

From granite pegmatites and nepheline syenites.

Dana VII, v. 1, p. 793-796. 

Lyndochite

A niobian-thorian variety of aeschynite(?)

Butler (1957); Fleischer (1966); Dana VII, v. 1, p. 787,

789-791. 

Sinicite

A variety of aeschynite enriched in U.

Chang (1963).

Compare Priorite, Niobo-aeschynite. 

BAOTITE

Ba4 (TiNb) 8 (Si4O12) C1O16

Tetragonal.

A rare silicate of Ba, Ti, and Nb with Cl.

Nb2 O5 =10.8, 11.5 percent.

From carbonatic veins and from quartz veins associated 

with alkalic rocks.

Vlasov (1964); Heinrich and others (1962); Semenov

and others (1961). 

Pao-t'ou-k'uang

Synonym of baotite.

Heinrich and others (1962). 

BEHIERITE

(Ta,Nb)BO4

Tetragonal (zircon type, but with smaller unit cell).

A borate of Ta and Nb.

From granite pegmatite.

Mrose and Rose (1961). 

BELYANKINITE

Ca(Ti,Zr,Si,Nb) 6O13 -14H2O

Orthorhombic or monoclinic (from optical data), 

poorly crystalline or amorphous?

(Nb,Ta) 2O5 =7.2-7.5 percent (type material).

From nepheline syenite pegmatite.

Gerasimovskii and Kazakova (1950).

Manganbelyankinite (Mn-belyankinite, manganobelyankinite)

A manganese-rich variety of belyankinite.

NbaOs^?^ percent.

Semenov (1957). 

See also Gerasimovskite.

BETAFITE

(U,Ca) 2 (Nb, Ti,Ta) 2 (O,OH,F) 7 

Cubic, commonly metamict.

A uranium-titanium-bearing pyrochlore; as redefined 

by Hogarth contains 15 percent or more U. Part 

of pyrochlore-betafite series.

Nb2O5 = 10-50 percent; Ta2O5 up to 20 percent. 

Found in granite pegmatites and in alkalic roiks and

carbonatites. 

Hogarth (1961 p. 610-633); Veen (1963, p. 35-36);

Dana VII, v. 1, p. 803-805. 

Blomstrandite

Synonym of betafite. 

Dana VII, v. 1, p. 803-805. 

Ellsworthite

Synonym of betafite; allied to hatchettolite.

Veen (1963, p. 36); Hogarth (1961, p. 631); Dana

VII, v. 1, p. 751, 755. 

Hatchettolite

An uranian-taiitalian-titanian variety of pyrochlore

similar to betafite, probably in part synonymous

with betafite and in part intermediate between

betafite and pyrochlore.

Veen (1963, p. 36); Hogarth (1961, p. 631); Dana

VII, v. 1, p. 751, 754. 

Meiideleyevite

Synonym of betafite. 

Dana VII, v. 1, p. 803-805. 

Rare-earth betafite

Near obruchevite and yttrohatchettolite in composition.

Vlasov (1964, p. 499, 501). 

Samiresite

Plumboaii variety of betafite. 

Dana VII, 1, p. 803-805. 

Tantalobetafite (tantalohatchettolite?)

Tantalian betafite, synonym of betafite. 

Veen (1963, p. 35). 

Titanobetafite

Betafite with high Ti content. 

Veen (1963, p. 26). 

Zirconium betafite

Zirconium-bearing betafite, ZrO2 up to 9.8 recent. 

Vlasov (1964, p. 507). 

BISMUTOTANTALITE 

Bi (Ta,Nb)O4 

Orthorhombic.

Probably isostructural with stibiotantalite. 

Ta2O5 =48.7 percent (theoretical). 

From granitic pegmatites. 

Dana VII, v. 1, p. 769-770. 

Ugandite

Synonym of bismutotantalite. 

Hey (1962, p. 221). 

COLUMBITE

(Fe,Mn)(Nb,Ta) 2 06 

Orthorhombic.

Part of the columbite-tantalite isomorphous series, 

Nb>Ta; includes ferrocolumbite with Fe>Mn and 

manganocolumbite with Mn >Fe. 

Nb2 O5 =78.9 percent (theoretical end member). 

Occurs widely in granites and granitic pegmatites. 

Dana VII, v. 1, p. 780-787.
GLOSSARY NIOBIUM ANlD TANTALUM MINERALS 33

COLUMBITE Continued 

Baierine (baierite)

Synonym of columbite.

Dana VII, v. 1, p. 780. 

Dianite

Synonym of columbite.

Dana VII, v. 1, p. 780. 

Ferro-ilmenite

Synonym of columbite.

Dana VII, v. 1, p. 780, 785. 

Greenland! te

Synonym of columbite.

Dana VII, v. 1, p. 780, 784. 

Hermannolite

Synonym of columbite.

Dana VII, v. 1, p. 780, 785. 

See also Magnocolumbite, Tantalite. 

DYSANALYTE (niobian perovskite)

(Ca,Ce,Na)(Ti,Nb,Ta)O3

Pseudocubic, possibly orthorhombic or monoclinic.

A niobotantalian perovskite in which Nb normally exceeds Ta but not Ti, and Ce and Na may be absent.

Found in alkalic rocks and carbonatites.

Dana VII, v. 1, p. 730, 732-734; Hey (1962); Nickel

and McAdam (1963). 

Compare Latrappite. 

EPISTOLITE

(Na) Ca) 3 .I (Nb,Ti) 2Si2O9-I (OH)J-n(H2O,Na3PO4 )

Monoclinic.

The niobium analog of murmanite.

(Nb,Ta) 2O5 = 33.6,32.3 percent.

From alkalic pegmatite.

Semenov and others (1961); Vlasov (1964, p. 547). 

EUXENITE (Y,Ca,Ce,U,Th)(Nb,Ti,Ta) 2O6 Orthorhombic, naturally metamict. Part of euxenite-polycrase series;

ratios, Ti:(Nb + Ta) lie between 2:3 and 1:1

Nb2O5 = about 21-34 percent; Ta2O5 =about 1-22 

percent.

From granitic rocks and pegmatites and placers derived 

from them.

Dana VII, v. 1, p. 787-792; Vlasov (1964, p. 458-470) 

Eschwegeite

Tantalian variety of euxenite; synonym of tanteuxenite.

Tavora (1951); Dana VII, v. 1. p. 792-793. 

Nuolaite

Variable mixtures of euxenite and obruchevite. 

Oliveiraite

Alteration product of euxenite.

Dana, VII, v. 1, p. 774, 791 

Tanteuxenite

Variety of euxenite with Ta substituting for Nb.

Dana VII, v. 1, p. 787, 789-791; Arnott (1950). 

Wiikite

Variable mixtures of euxenite and obrachevite. 

FERGUSONITE

(Y,Er,Ce,Fe)(Nb,Ta,Ti)O4 Tetragonal, naturally metamict.

Part of fergusonite-formanite series; Nb>Ta and 

Y>Er.

Contains up to 8 percent U and Th in substitution for 

Y and Er.

Nb2O5 =54.1 percent (theoretical end member).

Fairly common accessory mineral in granitic pegmatites.

Dana VII, v. 1, p. 757-762.

FERGUSONITE Continued 

Adelpholite

Synonym of fergusonite?

A poorly defined substance, possibly an altered mos'ite.

Dana VII, v. 1, p. 762, 778-779. 

Alpha-fergusonite

Synonym of fergusonite.

A naturally occurring nonmetamict tetragonal ferpusonite. Gorzhevskaya and others (1961). 

Arrhenite

An altered fergusonite.

Dana VII, v. 1, p. 762. 

Beta-fergusonite

A naturally occurring nonmetamict monoclinic polymorph of fergusonite.

Gorzhevskaya and others (1961). 

Bragite

Synonym of fergusonite.

Dana VII, v. 1, p. 757, 759, 761. 

Kochelite

Synonym of fergusonite.

Dana VII, v. 1, p. 757, 761. 

Risorite

A naturally metamict titanian variety of fergusonite.

Dana VII, v. 1, p. 757-758, 760-762. 

Rutherfordite

An altered fergusonite.

Dana VII, v. 1, p. 757, 761, 762. 

Sipylite

Synonym of fergusonite.

Dana VII, v. 1, p. 757, 759-762. 

Tyrite

Synonym of fergusonite.

Dana VII, v. 1, p. 757, 760-761. 

FERSMANITE

(Ca,Na) 2 (Ti,Nb) (Si05) (F,OH)

Monoclinic.

A titano-niobosilicate of Ca and Na with F (eome 

without Nb).

(Nb,Ta) 2 05 =15.4, 17.95 percent.

From alkalic pegmatite.

Vlasov (1964, p. 549); Hey (1962). 

FERSMITE

(Ca,Ce)(Nb,Ti) 2 (0,F) 6

Orthorhombic.

Isostructural with euxenite.

Nb2O5 =70.1, 71.5 percent in type material.

Found in syenite pegmatites and in carbonatites.

Bonshtedt-Kupletskaya and Burova (1946); Wambeke

(1965). 

FORMANITE

(Y,Er,U,Th,Ca)(Ta,Nb,Ti)O4

Tetragonal, naturally metamict.

Part of fergusonite-formanite series, Ta>Nb.

Ta2 05 =66.2 percent (theoretical end member).

From placers.

Dana VII, v. 1, p. 757-762. 

GE RASIMOVSKITE (niobobelyankinite)

(Mn,Ca) 2 (Nb,Ti) 5O12 -9H2O(?)

Related to belyankinite.

Nb2O5 =44.9 percent in type material.

Semenov (1957).
34 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

ILIMAUSSITE

Na4Ba2CeFeNb2Si8 028 -5H2 0

Partly metamict.

Nb2O5 =13.2 percent.

Found in n epheline-sodalite syenite.

E. I. Semenov, M. E. Kazakova, and R. A. Alexandrova

(written commun., 1967). 

ILMENORUTILE

(Ti,Nb,Ta,Fe) 2O4

Tetragonal.

Part of isomorphous series ilmenorutile-struverite with

Nb>Ta.

Nb2 05 as much as 33 percent; Ta2O5 as much as 14 

percent but most analyses are made on inhomogeiieous samples.

Occurs mostly in alkalic rocks and pegmatites. 

Cerny and others (1964); Dana VII, v. 1, p. 554, 557-

560. 

Niobo-rutile, rumongite

Synonyms of ilmenorutile. 

Hey (1962, p. 221). 

IXIOLITE

(Ta,Fe,Sn,Nb,Mn) 4 08 

Orthorhombic.

A disordered form of tantalite, commonly high in Sn. 

From granite pegmatites.

Nickel and others (1963a); Dana VII, v. 1, p. 778. 

KARNASURTITE

(Ce,La,Th) (Ti,Nb) (Al.Fe) (Si,P) 2 07 (OH) 4 -3H2O 

Hexagonal, metamict.

A hydrous silicate of rare earth elements, Th, Al, Ti, 

and Nb containing P; presumably related to huttonite, cheralite, and monazite. 

Nb2 05= 2.2-8.2 percent. 

From zoned aegirine-microcline-natrolite-hackmanite

pegmatites. 

Kuz'menko and Kozhanov (1959); Vlasov and others

(1959, p. 423-425). 

KOBEITE

(Y,Fe,U)(Ti,Nb,Ta) 2 (O,OH) 6 

Metamict.

Near euxenite-polyerase or aesehynite-priorite series 

in composition, but with low (Nb,Ta)2O5 content. 

(Nb,Ta) 2Os= about 5 percent. 

From granitic pegmatites, placers. 

Takubo and others (1950); Hutton (1957) 

LATRAPPITE

(Ca,Na)(Nb,Ti,Fe)O3 

Orthorhombic.

A newly denned member of the perovskite group containing dominant Ca and Nb. 

Nb2O5 = 43.9; TiO2 =10.1. 

Occurs in earbonatites. 

Nickel (1964). 

LOMONOSOVITE

(Na,Ca,Ba,K) 8 (Ti,Fe,Nb,etc.) 4 (Si,Al) 4P2 (O,F) 25 or

Na2 (Ti,Nb) 2Si2O9.Na3PO4 

Trielinic.

Part of lomonosovite-murmanite series. 

(Nb,Ta) 2O5 reaches about 6 percent m some varieties. 

From alkalie pegmatities. 

Gerasimovskii (1950). 

Beta-lomonosovite

Hydrous variety of lomonosovite. 

Gerasimovskii and Kazakova (1962).

LOMONOSOVITE Continued 

Metalomonosovite

Synonym of beta-lomonosovite.

Semenov and others (1961). 

Ortholomonosovite

Synonym of lomonosovite.

Semenov and others (1961). 

LOPARITE

(Na,Ce,Ca)(Ti,Nb)O3

Cubic.

A cerian-niobian perovskite with cerium-earth content 

near 30 percent.

(Nb,Ta) 2O5 =about 10 percent; Nb predominant.

Occurs in alkalic pegmatites.

Vlasov and others (1959, p. 332-339); Dana VII, v. 1, p.

730, 732-734. 

Irinite

A metamict thorian variety of loparite.

Borodin and Kazakova (1954). 

Metaloparite

A hydrated alteration product of loparite.

Gerasimovskii (1941). 

Nioboloparite

A niobian variety of loparite with Nb2O5 content as

much as 26 percent, but Ti> Nb.

Tikhonenkov and Kazakova (1957). 

LUESHITE

NaNb03

Orthorhombic (pseudocubic).

The sodium-niobium analog of perovskite.

(Nb,Ta) 2O5 reaches 80 percent; Nb predominant.

Occurs in alkalic rocks and earbonatites.

Safiannikoff (1959); Bargasarov and other? (1962);

Parker and others (1962). 

Igdloite

Synonym of lueshite.

Dan0 and S0rensen (1959). 

Natroniobite

NaNbO3 or NaNbaO5OH

Monoclinic; dimorph of lueshite? Structural affinities 

unknown.

Occurs in earbonatites.

Bulakh and others (1960); Kukharenko and others (1965). 

MAGNOCOLUMBITE

(Mg, Fe, Mn) (Nb, Ta) 2O6

Magnesium analog of columbite.

Nb2O5=70.6 percent; Ta2O5 = 10.45 percent.

Occurs in pegmatite that has assimilated dolo-mite.

Matias and others (1963). 

MIC ROUTE

(Ca,Na) 2 (Ta,Nb,Ti) 2 (O,OH,F) 7

Cubic.

Part of pyrochlore-microlite series.

Ta2O5=82.1 percent (theoretical end member).

From albitized granitic pegmatites.

Dana VII, v. 1, p. 748-757; Veen (1963, p. 26);

Bonshtedt-Kupletskaya (1966). 

Bismutomicrolite

Bismuthian variety of microlite; (Bi2Os=3.25 percent).

Vlasov (1964), p. 507). 

Djalmaite

Uranoan microlite or tantalian betafite?

Tavora (1950); Dana VII, v. 1, p. 805; Veen (1963, 

p. 36).
GLOSSARY NIOBIUM AND TANTALUM MINERALS 35

MICROLITE--Continued 

Haddamite

Synonym of microlite. 

Dana VII, v. 1, p. 748. 

Metasimpsonite

Synonym of microlite. 

Dana VII, v. 1, p. 748, 755. 

Neotantalite

Synonym of microlite. 

Dana VII, v. 1, p. 748, 755. 

Uranmicrolite

Synonym of djalmaite. 

Vlasov (1964, p. 507). 

MURMANITE

Na2 (Ti,Nb) 2Si2 09 .»H2 0 

Monoclinic.

Part of murmanite-lomonosovite series. 

(Nb,Ta) 2 O5 reaches about 10 percent in some analyses. 

From alkalic rocks, Kola peninsula, USSR. 

Es'kova (1959); Vlasov (1964, p. 544-547). 

Beta-murmanite

Of dubious validity; considered a weathering product

of beta-lomonosovite. 

Vlasov (1964, p. 546); Fleischer (1963). 

Metamurmanite

Synonym of beta-murmanite. 

Vlasov (1964, p. 544). 

NENADKEVICHITE

(Na.Ca) (Nb,Ti)Si2O7 -2H2 O

Orthorhombic (by optical methods).

Part of nenadkevichite-labuntsovite series;

Nb2 O5 : TiO2 = 2 or more.

Nb2O5 =24.05-24.6 percent (original analyses). 

From natrolite-albite pegmatite in aegirine lujavrite. 

Kuz'menko and Kazakova (1955); Semenov (1959);

Vlasov (1964, p. 533). 

Niob olabuntso vite

Member of nenadkevichite-labuntsovite series;

Nb2O5 : TiO,= l:3-l:2. 

Semenov (1959); Vlasov (1964, p. 533-535), 

NIOBO-AESCHYNITE

(Ce,Ca,Th)(Nb,Ti) 2O8 

Niobium analog of aeschynite. 

Nb2O5 =41.4 percent. 

Zhabin and others (1960). 

NIOBOPHYLLITE

(K,Na) 2 . 95 (Fe,Mn)e.35(Nb,Ti) 2 .o2 (Si,Al) 7 .7 o(0,OH,F) 3i

Triclinic.

The niobium analog of astrophyllite.

Nb2O6 =14.8 percent; Ta2 O5 =0.5 percent.

Found in paragneiss with albite, arfvedsonite, aegirineaugite, and pyrochlore. 

Nickel and others (1964). 

NIOBOZIRCONOLITE 

CaZr (Ti,Nb)jO7 

Pseudocubic, metamict. 

A niobian variety of zirconolite. 

Nb2O5 =24.8 percent; Ta2O6 =2.0 percent. 

From apatite-magnetite rocks of the Vuori-Yarvi massif,

U.S.S.R.

Borodin and others (1960). 

NIOCALITE

Ca4NbSi2010 (OH,F) 

Monoclinic.

NIOCALITE Contin ued

A silicate of Ca and Nb closely related to wohlerite,

hiortdahlite, and lavenite. 

Nb2O6 =16.6, 18.9 (type locality). 

From carbonatite, Oka district, Quebec. 

Nickel and others (1958). 

OBRUCHEVITE

(Y,Ca,U) 2 (Nb,Ti,Ta) 2 (0,OH,F) 7

Yttrium analog of pyrochlore.

Veen (1963, p. 37).

Nuolaite and wiikite are variable mixtures of euxeMte

and obruchevite. 

PANDAITE

(Ba,Sr) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7 

Barium analog of pyrochlore. 

Nb2O6= 65-67 percent; Ta2O6 =0.2-0.5 percent. 

From carbonatites. 

Veen (1963, p. 37). 

PISEKITE

A niobate-tantalate-titanate of U and rare earths vith

Th and Sn; no analysis. 

Tetragonal or monoclinic(?), metamict. 

From pegmatite with striiverite, beryl, tourmaPne,

monazite, and garnet. 

Dana VII, v. 1, p. 807-808; Seidl (1960); Bou^ka

(1960). 

PLUMBOMICROLITE

(Pb,Ca) (Ta,Nb) 2 (O,OH,F) 7 

Lead analog of microlite. 

Ta2O6= 50.4 percent; Nb2Os=ll.l percent. 

Safiannikoff and Wambeke (1961). 

POLYCRASE

(Y,Ca,Ce,U,Th) (Ti,Nb,Ta) 2O8

Orthorhombic, naturally metamict.

Part of euxenite-polyerase series; ratios Ti:(Nb+Ta)

lie between ! : 1 and 3:1.

Nb2O6 =about 4-20 percent; Ta2O6 =up to 23 percent. 

Found in granitic pegmatites. 

Dana VII, v. 1, p. 787-792. 

Tantalopolycrase

Variety of polycrase in which Ta replaces Nb. 

Dana VII, v. 1, p. 790, 791; Simpson (1938, p. 112). 

POLYMIGNYTE

Possibly (Ca,Fe,Ce) (Zr,Ti,Nb,Ta) 2O6

Orthorhombic, metamict.

A zirconium-titanium-niobium mineral of uncertain

affinities, possibly related to aeschynite or zirconolite. 

Nb2O6 =11.99, 6.37 percent and Ta2O5 =1.35, 42.17

percent in two analyses from Fredricksvarn, Norway. 

From alkalic rocks and pegmatites and granite pegmatite. 

Dana VII, v. 1, p. 764-766; Lima-de-Faria (1964, p.

45-46); Vlasov (1964). 

PRIORITE

(Y,Er,Ca,U,Th) (Ti,Nb) 2O8 

Orthorhombic, naturally metamic. 

Part of aeschynite-priorite series (yttrian). 

(Nb,Ta) 2O5 = 16-37 percent. 

From granite pegmatites and nepheline syenites. 

Dana VII, v. 1, p. 793-797. 

Blomstrandine

Also blomstrandinite. 

Synonym of priorite. 

Dana VII, v. 1, p. 793, 796.
36 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

PYROCHLORE

(Na,Ca,Ce) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7

Cubic.

Part of the pyrochlore-microlite series.

Nb2O5= 73.05 percent (theoretical end member).

From alkalic rocks and pegmatites, carbonatites, and 

albite-riebeckite granites.

Dana VII, v. 1, p. 747-757; Veen (1963); BonshtedtKupletskaya (1966). 

Azor-pyrrhite

Synonym of pyrochlore.

Dana VII, v. 1, p. 748, 754. 

Chalcolamprite

Variety of pyrochlore(?) containing Si and Zr; possibly 

mixture of minerals.

Dana VII, v. 1, p. 748, 754. 

Columbomicrolite

Synonym of pyrochlore.

Veen (1963, p. 26). 

Endeiolite

Probably altered pyrochlore.

Dana VII, v. 1, p. 748, 754. 

Fluochlore

Synonym of pyrochlore.

Dana VII, v. 1, p. 748. 

Hydrochlore

Synonym of pyrochlore.

Dana VII, v. 1, p. 748. 

Koppite

Cerian-ferrian variety of pyrochlore.

Veen (1963, p. 37); Dana VII, v. 1, p. 748, 750, 752,

754, 755. 

Marignacite

A cerian pyrochlore, probably altered.

Dana VII, v. 1, p. 748, 751, 752, 755; Veen (1963, p. 37). 

Niobpyrochlore

Synonym of pyrochlore.

Dana VII, v. 1, p. 748. 

Priazovite

Uranian pyrochlore rich in Y, synonymous with 

obruchevite ?

Veen (1963, p. 37). 

Pyrrhite

Synonym of pyrochlore.

Dana VII, v. 1, p. 748, 752, 754. 

Scheteligite

Titanian pyrochlore rich in Mn, Y, and Sb.

Veen (1963, p. 36); Dana VII, v. 1, p. 757. 

Uranpyrochlore

Uranium-bearing pyrochlore near hatchettolite in 

composition.

Vlasov (1964, p. 487-488); Dana VII, v. 1, p. 751, 754. 

Yttrobetafite

A variety of pyrochlore intermediate between pyrochlore 

and obruchevite.

Kalita and others (1962). 

Yttrohatchettolite

Yttrium-uranium-bearing pyrochlore with Nb and Ta 

nearly equal.

Vlasov (1964, p. 487-489).

Compare Obruchevite. 

RIJKEBOERITE

(Ba,Fe,Pb,U)(Ta,Nb,Ti,Sn) 2 (O,OH,H2 O) 7

Barium analog of microlite.

RIJKEBOERITE Continued

Ta2O5=7l.6 percent; Nb2O5 =5.9 percent.

Veen (1963, p. 135-137) 

SAMARSKITE

(Y,Fe,U)(Nb,Ti,Ta) 2 (O,OH) 6

Orthorhombic; normally metamict.

A titano-tantalo-niobate of Fe, Y, and U.

Nb:A = 27.8-46.4 percent; Ta2O5 = 1.8-27.0 percent.

From granite pegmatites.

Dana VII, v. 1, p. 797-800; Gorzhevskaya and

Sidorenko (1963). 

Ampangabeite

Synonym of Samarskite.

Dana VII, v. 1, p. 806-807; Wambeke (1960). 

Annerodite

Synonym of Samarskite.

Dana VII, v. 1, p. 797, 799. 

Calciosamarskite

A supposed calcian Samarskite, but X-ray pattern after 

ignition differs from that of samarakite and is similar 

to that of obruchevite.

Dana VII, v. 1, p. 772; Gorzhevskaya and Sidorenko

(1963). 

Eytlandite

Synonym of samarskite.

Dana VII, v. 1, p. 797. 

Hy dr osamars kite

An altered samarskite.

Dana VII, v. 1, p. 800. 

Ishikawaite

A variety of samarskite with high U and Fe content.

Gorzhevskaya and Sidorenko (1963); Dana VII, v. 1,

p. 766. 

Khlopinite

Also chlopinite, hlopinite.

A titanian variety of samarskite (?)

Dana VII, v. 1, p. 792. 

Nohlite

Probably a mixture, part of which is samarskite.

Dana VII, v. 1, p. 772-773. 

Nuevite

Synonym of samarskite.

Murdoch (1951). 

Plumboniobite

Probably a plumbian variety of samarskite.

Dana VII, v. 1, p. 800-801. 

Rogersite

An altered samarskite.

Dana VII, v. 1, p. 800; Heinrich and Quon (1963). 

Uranniobite

Synonym of samarskite.

Dana VII, v. 1, p. 797. 

Uranotantal

Synonym of samarskite.

Dana VII, v. 1, p. 797. 

Vietinghofite

A ferroan variety of samarskite.

Dana VII, v. 1, p. 800-801. 

Yttroilmenite

Synonym of samarskite.

Dana VII, v. 1, p. 763, 797. 

SHCHE RBAKOVITE

(K,Na,Ba) 3 (Ti,Nb) 2 (Si2 07) 2

Monoclinic(?) or Orthorhombic.
GLOSSARY NIOBIUM AND TANTALUM MINERALS 37

SHCHERBAKOVITE Continued

Part of shcherbakovite-batisite series.

(Nb,Ta) 2O5 = about 10 percent.

From pectolite-natrolite pegmatites associated with 

alkalic rocks.

Es'kova and Kazakova (1954) ;

Yakovlevskaya and Efimov (1963). 

SIMPSONITE

Al4 (Ta> Nb) 8 (0,OH,F) 14

Hexagonal.

Principally an oxide of Al and Ta.

Ta2 05 = 81.25 percent (theoretical).

From granite pegmatites.

Dana VII, v. 1, p. 771; Knorring and Hornung (1963). 

Calogerasite

Synonym of simpsonite.

Guimaraes (1944). 

STIBIOCOL UMBITE

Sb(Nb,Ta)O4

Orthorhombic.

Part of the stibiotantalite-stibiocolumbite series.

Nb2O5 =47.7 percent (theoretical end member).

From granitic pegmatites.

Dana VII, v. 1, p. 767-769. 

STIBIOTANTALITE

Sb(Ta,Nb)O4

Orthorhombic.

Part of the stibiotaiitalite-stibiocolumbite series.

Ta2O5 = 60.2 (theoretical end member).

From granitic pegmatites.

Dana VII, v. 1, p. 767-769. 

Stibiobismutotantalite

A bismuthian variety of stibiotantalite.

Bandy (1901). 

STRUTERITE

(Ti,Ta,Nb,Fe) 2O4

Tetragonal.

Part of isomorphous series ilmeiiorutile-stiiverite and 

partial series (?) rutile-tapiolite.

Nb2O5 as much as 9.3 percent; Ta2O5 as much as 38.2 

percent, but some analyses possibly are made on inhomogeneous samples.

Found largely in granitic rocks and pegmatites.

Cerny and others (1964); Dana VII, v. 1, p. 554, 557,

558, 560. 

Tantalorutile

Synonym of striiverite.

Hey (1962, p. 221). 

TANTALITE

(Fe,Mn)(Ta,Nb) 2O6

Orthorhombic.

Part of columbite-tantalite isomorphous series, Ta> 

Nb; includes ferrotantalite with Fe>Mn and manganotantalite with Mn>Fe.

Ta2O5 =86.1 (theoretical end member). Found in 

granitic pegmatites, especially late-stage albitic pegmatites containing Li and Be.

Dana VII, v. 1, p. 780-787. 

Alvarolite

Synonym of tantalite (manganoan).

Tavora (1955). 

Calciotantalite

Synonym of tantalite ?

Perhaps a mixture of tantalite and microlite.

Dana VII, v. 1, p 787.

TANTALITE Continued 

Harttantalerz

Synonym of tantalite.

Dana VII, v. 1, p. 780. 

Ildefonsite

Synonym of tantalite.

Dana VII, v. 1, p. 780. 

Siderotantalite

Synonym of tantalite.

Dana VII, v. 1, p. 780. 

TAPIOLITE

(Fe,Mn)(Ta,Nb) 2O6

Tetragonal, dimorph of tantalite.

Part of isomorphous series rutile-tapiolite; Ta > Nb.

Nb2O5 = 0-35 percent, rarely exceeding 11 percent; 

Ta2O5 up to 86 percent.

Occurs in granitic pegmatites.

Cerny and others (1964); Dana VII, v. 1, p. 775-778. 

Mossite

Doubtful apecies.

Niobian analog of tapiolite.

Original analysis in doubt; possibly does not occur in 

nature.

Cerny and others (1964); Wambeke and others (19°4,

p. 75); Dana VII, v. 1, p. 775-777. 

Niobotapiolite

Niobian variety of tapiolite.

Synonymous with mossite.

Vlasov (1964, p. 438). 

Skogbolite

Synonym of tapiolite.

Dana VII, v. 1, p. 775-778. 

Compare Ixiolite, Wodginite. 

THOREAULITE

Sn(Ta,Nb) 2O7

Monoclinic.

An oxide of Sn, Ta, and Nb.

Ta2O5 = 27.8-72.8 percent; Nb2O5 up to 40.6 percent.

From tin-bearing pegmatite.

Dana VII, v. 1, p. 802; Thoreau and others (1950). 

WESTGRENITE

(Bi,Ca)(Ta,Nb) 2O6 (OH)

Bismuth analog of microlite.

Ta2O5 = 45.5 percent; Nb2O5 = 5.65 percent.

From lithium-bearing pegmatite.

Knorring and Mrose (1962). 

WODGINITE

(Ta, Sn, Mn, Nb,Fe,Ti) i6O32

Monoclinic.

A "polymorph" of tantalite, commonly with high Sr 

content.

Ta2O5 =67.5-70.1; Nb2O5 -7.1-1.35 percent,

Occurs in granitic pegmatites.

Nickel and others (1963b). 

Olovotantalite

Synonym of wodginite ?

Tin-manganese with X-ray pattern similar to that of 

wodginite

Ta2O5 =62.5; Nb2O5 =12.5 percent.

Matias (1961); Nickel and others (1963b, p. 401). 

WO'HLERITE (woehlerite)

NaCa2 (Zr,Nb)(Si2O7)O,F

(Nb,Ta) 2O5= 12.8-14.6 percent.

From alkalic pegmatite and nepheline syenite.

Gossner and Kraus (1934); Nickel and others (1958).
38 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

YTT ROT ANT ALITE

(Y,Fe)(Nb,Ta)O4 (approximately).

Orthorhombic, metamict.

A niobate-tantalate of Y (and other rare earths), Ca, 

Fe, U, Th, Mn, and other elements with minor substitution of W, Zr, and Sn for Nb and Ta.

Nb2O5 = 12-20 percent; Ta2 O5 =39-46 percent.

From granite pegmatites.

Dana VII, v. 1, p. 763-764; Vlasov (1964, p. 521-524). 

Hjelmite (hielmite)

A doubtful variety of yttrotantalite.

Some hjelmite from Norway proved to be a mixture of 

pyrochlore and tapiolite; however, this was not the 

type material from Sweden.

Dana VII, v. 1, p. 779-780; Matias (1961).

PART IH. MINERALS REPORTED TO CONTAIN 1-5 

PERCENT NIOBIUM AND TANTALUM

Astrophyllite

Baddeleyite

Brookite

Cassiterite

Catapleiite

Chevkinite

Chlorite

Elpidite

Eudialyte

Freudenbergite

Hematite

Hiortdahlite

Ilmenite

Keilhauite

Kimzeyite

Kupletskite

Labuntsovite

Lavenite

Lorenzenite 

Lovchorrite 

Manganosteenstrupine 

Melanocerite

Mosandrite

Perovskite

Ramsayite

Rinkite

Rinkolite

Rutile

Sphene

Thortveitite

Titanolavenite

Titanorhabdophane

Triplite

Tritomite

Tundrite

Vernadite

Vinogradovite

Vudyavrite

Wolframite

Yttrotitanite

Yuksporite

Zircon

(K,Na) 2 (Fe,Mn) 4 (Ti,Zr)Si4O14 (OH) 2

ZrO2

Ti02

SnO2

(Na2 ,Ca)ZrSi3O9 .2H2O

(Fe,Ca)(Ce,La,Y) 2 (Si,Ti) 3 010

(Mg,Fe) 5Al(Al,Si) 3 010 (OH) 8

Na2ZrSi6OJ2 (OH) 6

(Ca,Na,Ce) 5 (Zr,Fe) 2 Si6 (O,OH,Cl) 20

Na2Fe2Ti7O18

Fe2 03

(Ca,Na) 13Zr3Si 9 (0,OH,F) 38

FeTiO3

Yttrian Sphene.

Ca3 (Zr,Ti) 2 (Al,Fe,Si) 3O12

(K,Na) 2 (Mn,Fe)4TiSi4O14 (OH) 2

(K,Na,Ba)TiSi2 (O,OH) 7.i/2H2O

A complex silicate of Zr, Na, and Ca,

also containing Ti, Nb, Fe, Mn, and F. 

Na2 (Ti,Zr) 2Si2O9 

Mosandrite.

(La,Th,Ca) MnSiO3 (OH) 3 -2H2O 

Silicate, borate, tantalate, fluoride, etc.

of Ca and rare earths. 

(Na,Ca,Ce) 3TiSi2O7 (O,F) 

CaTiO3 

Lorenzenite. 

Mosandrite. 

Mosandrite. 

TiO2

CaTiSiO5 

(Sc,Y) 2Si207

(Na,Mn,Ca) (Zr,Ti) (SiO4) 2F 

Tundrite. 

(Mn,Fe) 2 (PO4)F 

A silicate, borate, and fluoride of Ca,

rare earths, and Th. 

(Ce,La,Nd) 2Ti(Si,P) (O,OH) 7.4H2O 

MnO2.nH2O(?) 

Na5Ti4AlSi6O24 .3H2O 

Altered Mosandrite(?) 

(Mn,Fe)WO4 

Yttrian Sphene. 

A silicate and fluoride of Ca, Sr, Ba,

and alkalis (?) 

ZrSiO4

Zirconolite 

Zirfesite

CaZrTi2 O7 

(ZrO2 ,Fe2O3)SiO2 -nH2O

PART IV. MINERALS IN WHICH NIOBIUM AND 

TANTALUM HAVE BEEN DETECTED IN QUANTITIES 

LESS THAN 1 PERCENT

Aegirine

Allanite

Amblygonite

Anatase

Arfvedsonite

Biotite

Erikite

Garnet (almandine) 

Hisingerite 

Kaolinite 

Lamprobolite

Lamprophyllite

Lepidolite

Leucosphenite

Magnetite

Muscovite

Nontronite

Phlogopite

Polylithionite

Riebeckite

Scheelite

Seidozerite

Thorianite

Thorite

Titano magnetite

Tourmaline

Tungstite 

Vlasovite

Si2O6

(Ca,Ce) 2 (Al,Fe) 3Si3O12 (OH) 

(Li,Na)AlPO4 (F,OH) 

TiO2

Na3Fe+24Fe+3 Si 8O22 (OH) 2 

K2 (Mg,Fe+',Al,Fe+3) 4-6 (Si,Al) 8 020 (OH) 4 

A doubtful phosphate and silicate of rare

earths. 

Fe3Al2 (SiO4) 3 

Fe2 Si2O5 (OH) 4 .2H2 O (?) 

Al2Si2O5 (OH) 4 

(Ca,Na,K) 2 -3 (Mg,Fe+3,Al) 5 (Si,Al) 8

022 (0,OH) 2 

Na2SrTiSi2O8

K(Li,Al) 3 (Si,Al) 4 010 (F,OH) 2 

Na3CaBaBTi3Si9O29 

Fe3 O4

KAl3Si3 010 (OH) 2 

(Fe,Al) 2 (Si,Al) 4O10 (OH) 2 .riH2O 

KMg3AlSi3O10 (OH) 2 

K2Li4Al2Si 8O20 (O,OH,F) 4 

Na2 (Fe+2 ,Mg) 3Fe+32Si8O22 (OH) 2 

CaWO4

Na8Zr3Ti3 Mn2 Si 8O32F4 

ThO2 

ThSiO4 

(Fe,Ti) 3 04 

(Na,Ca)(Li,Mg,Fe+2,Al) 3 (Al,Fe+3) 6

B3Si6027 (O,OH,F) 4 

H2WO4 

Na2ZrSi4Ou

REFERENCES FOR GLOSSARY OF NIOBIUM AND 

TANTALUM MINERALS

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Bargasarov, Yu. A., Gaidukova, V. S., Kuznetsova, N. N., and

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Bonshtedt-Kupletskaya, E. M., 1966, Systematization of the

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Bonshtedt-Kupletskaya, E. M., and Burova, T. A., 1946,

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Borodin, L. S., Bykova, A. V., Kapitonova, T. A., and Pyatenko,

Yu. A., 1960, New data on zirconolite and its niobian

variant: Akad. Nauk SSSR Doklady, v. 134, p. 1188-1191

(in Russian).
REFERENCES FOR GLOSSARY OF NIOBIUM AND TANTALUM MINERALS 39

Borodin, L. S., and Kazakova, M. E., 1954, Irinite a new

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Bouika, Vladimir, 1960, Pisekite: Ceskoslovenska Akad. Ved.

Rozpravy, Rada Mat. Prirod. Ved., v. 70, no. 3, 35 p. 

Bulakh, A. G., Kukharenko, A. A., Knipovich, Yu. N., Kondrateva, V. V., Baklanova, K. A., and Baranova, E. N.,

1960, Some new minerals in carbonatites of the Kola

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Butler, J. R., 1957, Rare earths and thorium in lyndochite: Am.

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Chang, Pei-Shan, 1963, Dimorphism and isomorphism in the

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Dan0, M., and S0rensen, H., 1959, An examination of some

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Es'kova, E. M., 1959, Minerals of the lomonosovite-murmanite

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123 (in Russian).

 1964, Niobium, in Geochemistry, mineralogy, and 

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Es'kova, E. M., and Kazakova, M. E., 1954, Shcherbakovite a 

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Fleischer, Michael, 1963, New mineral names: Am. Mineralogist, 

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 1966, Rare earths in the aeschynite-priorite series. The 

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Gerasimovskii, V. I., 1941, Metaloparite, a new mineral from 

the Lovozero tundras: Acad. Sci. SSSR Comptes Rendus, 

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 1950, Lomonosovite, a new mineral: Akad. Nauk SSSR

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Gerasimovskii, V. I., and Kazakova, M. E., 1950, Belyankinite 

a new mineral: Akad. Nauk SSSR Doklady, v. 71, no. 5,

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 1962, Beta-lomonosovite: Akad. Nauk SSSR Doklady, 

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Gorzhevskaya, S. A., and Sidorenko, G. A., 1963, Main properties of minerals of the samarskite structural type: Vses. 

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Gossner, B., and Kraus, O., 1934, Beitrag zur Kenntnis der 

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p. 135-136.

Heinrich, E. W., Boyer, W. H., and Crowley, F. A., 1962, 

Baotite (pao-t'ou-k'uang) from Ravalli County, Montana: 

Am. Mineralogist, v. 47, nos. 7-8, p. 987-993.

Heinrich, E. W., and Quon, S. H., 1963, Rogersite = \~Teinschenkite: Am. Mineralogist, v. 48, p. 1168-1170.

Hey, M. H., 1955, 1962, An index of mineral species and varieties 

arranged chemically: London, British Mus. (Nat. History).

 1963, Appendix to the second edition of an index of 

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Hogarth, D. D., 1961, A study of pyrochlore and betafite: 

Canadian Mineralogist, v. 6, p. 610-633.

Hutton, C. O., 1957, Kobeite from Paringa River, South Westland, New Zealand: Am. Mineralogist, v. 42, p. 342-353.

Kalita, A. R., Bykova, A. V., and Kukharchik, M. V., 1962, 

Varieties of pyrochlore and betafite in pegmatites: Akad. 

Nauk SSSR Inst. Mineral., Geokhim. i Kristalol-him. 

Redkikh Elementov Trudy, v. 8, p. 210-211 (in Russian).

Knorring, Oleg von, and Hornung, G., 1963, Simpsonite and 

stibiotantalite from Benson pegmatite mine, Mtoko, Southern Rhodesia: Mineralog. Mag., v. 33, p. 458-466.

Knorring, Oleg von, and Mrose, M. E., 1962, Westgrenite and 

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IPinskii, G. A., Sergeev, A. S., and Abakumova, N. B., 

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Kuz'menko, M. V., and Kazakova, M. E., 1955, Nenrdkevichite a new mineral: Akad. Nauk SSSR Doklady, v. 

100, p. 1159-1160 (in Russian).

Kuz'menko, M. V., and Kozhanov, S. I., 1959, The new 

mineral, Karnasurtite: Akad. Nauk SSSR Inst. Mineral., 

Geokhim. i Kristalokhim. Redkikh Elementov Trudy, v. 2, 

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Lima-de-Faria, J., 1964, Identification of metamict minerals by 

x-ray powder photographs: Lisbon, Junta de Investigates 

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45-46.

Matias, V. V., 1961, Tin-tantalite (olovotantalit), a new variety 

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Mrose, M. E., and Rose, H. J., Jr., 1961, Behierite, (Ta,Nb)BO4 , 

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1961: Geol. Soc. America Spec. Paper 68, p. 235.

Murdoch, Joseph, 1951, Notes on some California minerals 

Nuevite-samarskite; trona and hanksite; gay-lussite: Am. 

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Nickel, E. H., 1964, Latrappite a proposed new name for- the 

perovskite-type calcium niobate mineral from the Oka area 

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from Oka, Quebec; a new classification for minerals of the 

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683-697.
40 GEOCHEMISTRY OF NIOBIUM AND TANTALUM

Nickel, E. H., Rowland, J. F., and Charette, D. J., 1964, Niobophyllite the niobium analogue of astrophyllite; a new mineral from Seal Lake, Labrador: Canadian Mineralogist, v. 

8, pt. 1, p. 40-52.

Nickel, E. H., Rowland, J. F., and McAdam, R. C., 1963a, 

Ixiolite a columbite substructure: Am. Mineralogist, v. 

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 1963b, Wodginite a new tin-manganese tantalate from 

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composition and crystallography of niocalite: Canadian 

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ed., v. I: New York, John Wiley & Sons, Inc., 834 p.

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INDEX OF MINERAL NAMES IN GLOSSARY

Adelpholite. See Fergusonite. 

Aegirine._______________________

Aeschy nite_ _____________________

Allanite. _______________________

Alpha-fergusonite. See Fergusonite. 

Alvarolite. See Tantalite. 

Amblygonite_ ___________________

Ampangabeite. See Samarskite. 

Anatase._______________________

Annerodite. See Samarskite.

Arf vedsonite. ___________________

Arrhenite. See Fergusonite. 

Astrophyllite. ____________________

Azor-pyrrhite. See Pyrochlore.

Baddeleyite_ ____________________

Baierine (Baierite). See Columbite. 

Baotite. ________________________

B

Behierite. _________________________

Belyankinite_ ______________________

Beta-fergusonite. See Fergusonite. 

Betafite___________________________

Beta-lomonosovite. See Lomonosovite. 

Beta-murmanite. See Murmanite. 

Biotite.___________________________

Bismutomicrolite. See Microlite. 

Bismutotantalite___ __________

Blomstrandine. See Priorite. 

Blomstrandite. See Betafite. 

Bragite. See Fergusonite. 

Brookite. _____________________

Calciosamarskite. See Samarskite. 

Calciotantalite. See Tantalite. 

Calogerasite. See Simpsonite. 

Cassiterite_ _ ____________________

Catapleiite. _ ____________________

Chalcolamprite. See Pyrochlore. 

Chevkinite_ _ _ __ _ _ _ ____________

Chlorite. _______________________

Columbite- _____________________

Columbomicrolite. See Pyrochlore.

D

Dianite. See Columbite. 

Djalmaite. See Microlite. 

Dysanaly te_ ___________

E

Ellsworthite. See Betafite. 

Elipidite- ________________

Endeiolite. See Pyrochlore. 

Epistolite__ ______________

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Erikite. __________________

Eschwegeite. See Euxenite. 

Eschynite. See Aeschynite. 

Eudialyte. ________________

Euxenite__ _ _____________

Eytlandite. See Samarskite.

Fergusonite- _____________ _ _

Ferrocolumbite. See Columbite. 

Ferro-ilmenite See Columbite. 

Ferrotantalite. See Tantalite. 

Fersmanite___ _ _____________

Fersmite_ __________________

Fluochlore. See Pyrochlore. 

Formanite. __________________

Freudenbergite _______________

F

G

Garnet.___________________

Gerasimo vskite_ __________

Greenlandite. See Columbite.

Haddamite. See Microlite. 

Harttantalerz. See Tantalite. 

Hatchettolite. See Betafite. 

Hematite ___________________________

Hermannolite. See Columbite. 

Hiortdahlite___ ____________________

Hisingerite. _ __-__--_____----------_-

Hjelmite (hielmite). See Yttrotantalite. 

Hydrochlore. See Pyrochlore. 

Hydrosamarskite. See Samarskite.

Igdloite. See Lueshite. 

Ildefonsite. See Tantalite. 

Ilimaussite_ _ _-________--

Ilmenite. _________________

Ilmenorutile__ _ _ _________

Irinite. See Loparite. 

Ishikawaite. See Samarskite. 

Ixiolite. _______----__--_--

K

Kaolinite_ _______________

Karnasurtite -_ __________

Keilhauite- __-_--_----_--

Khlopinite. See Samarskite. 

Kimzeyite- ______-__----_.

Kobeite. _________-_---_-.

Kochelite. See Fergusonite. 

Koppite. See Pyrochlore. 

Kupletskite. ___-_-_-___---

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41
42 INDEX

Labuntsovite_ _ __________

Lamprobolite_ __ _________

Lamprophyllite _ _________

Latrappite_ _______________

Lavenite__ __ ______________

Lepidolite__ _ _ ___________

Leucosphenite. ____________

Lomonosovite_ ____________

Loparite_ _________________

Lorenzenite. _ _____________

Lovchorrite. ______________

Lueshite. ________-___---__

Lyndochite. See Aeschynite.

M

Magnetite. ___--_----------__---_____--____________

Magnocolumbite__ ________________________________

Manganbelyankinite (Mn-belyankinite, manganobelyankinite). See Belyankinite. 

Manganocolumbite. See Columbite. 

Manganosteenstrupine___ _ _________________________

Manganotantalite. See Tantalite.

Marignacite. See Pyrochlore.

Melanocerite_ _____-_---_--_--______________________

Mendeleyevite. See Betafite.

Metalomonosovite. See Lomonosovite.

Metaloparite. See Loparite.

Metamurmanite. See Murmanite.

Metasimpsonite. See Microlite.

Microlite- ___-___--------_-----_-_-________________

Mosandrite_ _____----_----_------____---___________

Mossite. See Tapiolite.

Murmanite. _______________________________________

Muscovite.__-___-----__-----_-_______-_-__________

N

Natroniobite. See Lueshite. 

Nenadkevichite_ _ _________________________________

Neotantalite. See Microlite. 

Niobian perovskite. See Dysanalyte. 

Niobian zirconolite. See Niobozirconolite. 

Niobo-aeschynite. __--___---_--_____________________

Niobobelyankinite. See Gerasimovskite. 

Niobolabuntsovite. See Nenadkevichite. 

Nioboloparite. See Loparite. 

Niobophyllite. _____---___------______-_--__________

Niobo-rutile. See Ilmenorutile.

Niobotapiolite. See Tapoilite.

Niobozirconolite- ___________________________________

Niobpyrochlore. See Pyrochlore.

Niocalite. ___-___----___-____________-----__-______

Nohlite. See Samarskite.

Nontronite_ ______________________________________

Nuevite. See Samarskite.

Nuolaite. See Euxenite and Obruchevite.

O 

Obruchevite__ --------_-__-___-_____--____________

Oliveiraite. See Euxenite. 

Olovotantalite. See Wodginite. 

Ortholomonosovite. See Lomonosovite.

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Pandaite._______-__---___

Pao-t'ou-k'uang. See Baotite. 

Perovskite_ ________________

Phlogopite. ________________

Pisekite. __________________

Plumbomicrolite ____________

Plumboniobite. See Samarskite. 

Polycrase. _____-__-_-_---____

Polylithionite. _______________

Polymignyte- ________________

Priazovite. See Pyrochlore. 

Priori te__ _ _________________

Pyrochlore__ _ __________________

Pyrrhite. See Pyrochlore.

R 

Ramsayite__ _ _________________

Rare-earth betafite. See Betafite. 

Riebeckite_ ____________________

Rijdeboerite. __________________

Rinkite_____-_____-----_______.

Rinkolite_ _________--_---____

Risorite. See Fergusonite. 

Rogersite. See Samarskite. 

Rumongite. See Ilmenorutile. 

Rutherfordite. See Fergusonite. 

Rutile___ _ __________--_--_-__

S 

Samarskite. _ _________________________

Samiresite. See Betafite.

Scheelite. ____________------___________.

Scheteligite. See Pyrochlore.

Seidozerite.____________________________

Shcherbakovite_ __-__-_-__--______.___--_

Siderotantalite. See Tantalite. 

Sinipsonite___ _ _________________________

Sinicite. See Aeschynite.

Sipylite. See Fergusonite.

Skogbolite. See Tapiolite.

Sphene_ _______________________________

Stibiobismutotantalite. See Stibiotantalite. 

Stibiocolumbite____ _ ____________________

Stibiotantalite___ _ ______________________

Struverite_.___ _______ __________ ________

Tantalite. ______________________

Tantalobetafite. See Betafite. 

Tantalohatchettolite. See Betafite. 

Tantalopolycrase. See Polycrase. 

Tantalorutile. See Striiverite. 

Tanteuxenite. See Euxenite. 

Tapiolite_ ___________------____.

Thoreaulite_ _________-_-___--__-

Thorianite. _____________________

Thorite ----------------_----_

Thortveitite_ ____________

Titanobetafite. See Betafite. 

Titanolavenite__ _ _-_'_-_-_

Titanomagnetite. _ _________

Titanorhabdophane, _______

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INDEX 43

Tourmaline.

Tritomite. ____________

Tundrite __ _ _ ________

Tungstite__ _ __________

Tyrite. See Fergusonite.

U

Ugandite. See Bismutotantalite. 

Uranmicrolite. See Microlite. 

Uranniobite. See Samarskite. 

Uranotantal. See Samarskite. 

Uranpyrochlore. See Pyrochlore.

V 

Vernadite__ ___________________

Vietinghofite. See Samarskite. 

Vinogradovite_ ________________

Vlasovite. ____________________

Vudyavrite__________________

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Westgrenite

W

Wiikite. See Euxenite and Obruchevite. 

Wodginite__

Wohlerite--_-__-

Wolframite

Y

Yttrobetafite. See Pyrochlore. 

Yttrohatchettolite. See Pyrochlore. 

Yttroilmenite. See Samarskite. 

Yttrotantalite

Zirconium betafite

Zirfesite_ - _

Z

. See Betafite.

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U.S. GOVERNMENT PRINTING OFFICE: 1968