Interpretation of the Composition 

of Lithium Micas

GEOLOGICAL SURVEY PROFESSIONAL PAPER 354-E
Interpretation of the Composition 

of Lithium Micas

By MARGARET D. FOSTER

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 354-E

Relations of lithian muscovites ana 

lepidolites, and of siderophyllites, 

protolithioniteS) zinnwaldites, and 

lepidolitesy based on published analyses

UNITED STATES GOVERNMENT PRINTING QFFICE, WASHINGTON : 1960
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D.C.
CONTENTS

Abstract_ ________________________________________

Introduction- ______----____-_-_-____-______________

Calculation of formulas__-____---_____________-__..___

Aluminum lithium micas__________________________

Interpretation of composition of lepidolites based on 

end members_-_-__-_____-________-____-__._

Compositional changes shown by the analyses.-____

Hypothetical Li-(octahedral Al) replacement ratios. _

Relation of Li to other constituents in calculated

formulas__-__________________________________

Relation between Li and octahedral AL _______

Relation between (Li R+2) and Si____._-__- 

Relation between Li and total Al_____________

Relation between Li and occupied octahedral 

sites in excess of 2.00___-___-_________-____

Relation between Li.O and F_______________

Relation between LijO content, octahedral occupancy, and structure-_________________________

Discussion.____________________________________

Ferrous lithium micas_______________________________

Previous interpretations of composition.___________

Compositional changes shown by analyses---------

Page 

115 

115

115

116

116

117

117

119

119

121

121

122

122

122

126

127

127

129

Page

Ferrous lithium micas Continued

Relation between ferrous lithium micas, siderophyllites, and aluminian lepidomelanes._________ 120

Compositional relations in siderophyllites and ferrous

lithium micas-_______________________________ 130

Relation between Li and trivalent octahedral

cations-_________________________________ 130

Relation between Li and Fe+2 ________________ 130

Relation between Li and Si-_____-__--_--_-__ 131

Hypothetical Fe+2-Li replacement ratios-__________ 131

Siderophyllite-lepidolite isomorphous series_-__-___- 132 

Siderophyllites and lepidomelanes_____________ 134

Protolithionites- ____________________________ 135

Zinnwaldites_ ______________________________ 136

Ferroan lepidolite (cryophyllite)______________ 136

Relation between aluminum lithium micas and ferrous

lithium micas--__--__--_-_--------------_-..--_-_- 137

Unusual lithium micas______-__--_-________- ______ 139

Summary. __________________________________________ 140

References cited-_______-______-_-___-_-__.__..______ 141

Index-_---__-__-_--_-_---__---__--_-____-_--.______ 147

ILLUSTRATIONS

Page

FIGURE 25. Relation between octahedral sites occupied by Li and vacated by Al in aluminum lithium micas.__.__..______ 120

26. Relation between (Li R+2) and Si in aluminum lithium micas__-__--___-__-_--_------_-____--____-.--_-__ 121

27. Relation between the number of formula sites occupied by Li and R+3 in aluminum lithium micas. ____..____ 122

28. Relation between Li and octahedral occupancy in excess of 2.00 in aluminum lithium micas___-_-____-._______ 123

29. Relation between Li20 and F in aluminum lithium micas----__---_--_-_---__-_-__---___--_ ____.._ 123

30. Relation between F and H.O+ in aluminum lithium micas.__________-_-__________--__-_-__---___..__---_ 123

31. Relation between Li occupancy, octahedral occupancy, and structural type in Stevens' and Berggren's samples, 125

32. Histograms of selected formulas showing the relation of lithian muscovites and lepidolites-__________________ 127

33. Relation between Li, R+2 (Fe+2, Mn+2, Mg), and octahedral R+3 (Al, Fe+3) + Ti+4 in aluminum lithium micas__ 128

34. Relation between Li and octahedral R+3 cations in siderophyllites and ferrous lithium micas_________.. 130

35. Relation between Li and Fe+2 in siderophyllites and ferrous lithium micas_________________________________ 130

36. Relation between Li and Si in siderophyllites and ferrous lithium micas__________________________________ 131

37. Relation between Li, R+2 (Fe+2, Mn+2, Mg), and octahedral R+3 (A1, Fe+3) + Ti+4 in siderophyllites and ferrous

lithium micas.-_-___-__-______-____-_-_--_____-___--____-_______-____-_-----_-_-_-___--__---___-, 131

38. Histograms of selected formulas representing steps in the siderophyllite-lepidolite series____________________ 134

39. Relation between Li, R+2 (Fe+2, Mn+2, Mg), and octahedral R+3 (A1, Fe+3) + Ti+* in lithium micas...-.-____-_ 138

ra
IV CONTENTS

TABLES

Page 

TABLE 1. Relation between Li2O content, octahedral occupancy, and structure of lithium micas analyzed by Stevens 124

2. Comparison of Li occupancy, Li-(octahedral Al) replacement ratio, and structure--------------------------- 126

3. Selected formulas illustrating relation between lithian muscovites and lepidolites_.__-_-_-_---___--_ .__ 126

4. Selected formulas representing steps in the siderophyllite-lepidolite series ------ _____-._-__-______ .___ 133

5. Analyses of lithian micas that do not fit in the aluminum lithium or ferrous lithium series._._-____-____-__-. 139

6. Analyses, with data for writing formulas, of aluminum lithium micas used in interpretation of composition (in

order of increasing Li2O content)-__-----_-___---_----_------_-------------------------------------- 142

7. Analyses, with data for writing formulas, of siderophyllites and ferrous lithium micas used in interpretation of

composition (in order of increasing Li2O content)__-_____--_--_--------------------------------------- 144

8. Analyses, with data for writing formulas, of siderophyllites and ferrous lithium micas not used in interpretation

of composition (in order of increasing Li2O content)-.-------------------------------------------------- 146
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

INTERPRETATION OF THE COMPOSITION OF LITHIUM MICAS

By MARGARET D. FOSTER

ABSTRACT

A study of more than 100 analyses of lithium micas reported in 

the literature indicates that, compositionally, most of the lithium 

micas may be interpreted as if derived by isomorphous replacement from muscovite or siderophyllite.

Starting with muscovite, analyses and formulas of aluminum 

lithium micas, arranged in order of increasing Li content, are 

characterized by decrease in octahedral Al and in tetrahedral Al 

and by increase in Si and in octahedral occupancy. These 

changes can be interpreted as the result of progressive replacement of octahedral Al by Li, in ratios varying between 2 and 3 

Li for 1 octahedral Al. The aluminum lithium micas are not, 

however, members of a continuous isomorphous series. The 

series is interrupted about halfway between an octahedral occupancy of 2.00 and 3.00 by a change in structure from muscovite 

to lepidolite. The term "lithian" muscovite is given to aluminum 

lithium micas having a muscovite structure.

Starting with siderophyllite, or other trioctahedral micas 

having high Fe+2 and very low Mg content, analyses and formulas 

of ferrous lithium micas, arranged in order of increasing Li 

content, are characterized by decrease in Fe+2, decrease in 

tetrahedral Al, increase in Si, and increase in octahedral occupancy. These changes can be interpreted as the result of progressive replacement by Li+I of Fe+2 , at an average replacement 

ratio of 2.0 Li+l for 1.5 Fe+2 . As there is less difference between the number of positive charges carried by the replacing cations and the replaced cations than in the aluminum 

lithium micas, the change in composition and the increase in 

octahedral occupancy is less in the ferrous lithium micas. The 

prototype, siderophyllite, is structurally trioctahedral, and, as 

replacement tends to increase octahedral occupancy, the ferrous 

lithium micas are also trioctahedral and no structural adjustments are necessary. The ferrous lithium mica series is, therefore, not broken as is the aluminum lithium mica series. Varietal 

definitions based on octahedral sites occupied by Li+l in the halfcell formula are: lithian siderophylite, having fewer than 0.25 

sites occupied by Li+1, protolithionite, having between 0.25 and 

0.75 sites occupied by Li+1, zinnwaldite, having between 0.75 

and 1.25 sites occupied by Li+l, and lepidolite, having more than 

1.25 sites occupied by Li+1 .

The high-Li members of both series are lepidolites. Thus 

lepidolites may be interpreted as if derived from muscovite or 

from siderophyllite.

INTRODUCTION

This study of the compositional and layer-charge 

relations of lithium-bearing micas is an extension of 

similar studies by the writer of the compositional and

layer-charge relations of the dioctahedral potassium 

micas (Foster, 1956) and of the trioctahedral micas 

(Foster, 1960). In the study of the dioctahedral potassium micas, the effect of octahedral replacement of trivalent by bivalent cations on the charge relation and 

composition of the constituent layers was studied in 

detail, and it was shown that these micas can be classified and correlated on the basis of the relation between 

the charges on their tetrahedral and octahedral layers, 

and that these micas are members of, and form, a trisilicictetrasilicic series. In the study of the trioctahedral 

micas, the effect of octahedral replacement of bivalent 

by trivalent cations on the charge relations and composition of the constituent layers was studied in detail and 

it was shown that the trioctahedral micas accommodate the additional number of positive charges carried 

by trivalent cations, compared with bivalent cations, 

in two quite different ways, and that the phlogopites, 

biotites, siderophyllites, and lepidomelanes form a 

complete magnesium-replacement system, in which 

Mg+2 is gradually and completely replaced by bivalent 

and trivalent cations.

It is the purpose of the present paper to present a 

similar study of the composition and layer-charge 

relations of the lithium micas.

CALCULATION OF FORMULAS

For the present study about 80 analyses of aluminum 

lithium micas and about 45 analyses of ferrous lithium 

micas were collected from the literature, and formulas 

were calculated from these analyses by the method 

devised by Marshall (1949, p. 58) and modified by the 

author. This method is described in detail in a previous 

paper of this series (Foster, 1960). Most of the discussion of the compositional characteristics of thesanalyses in the present paper is based on the calculated 

half-cell formulas.

Attention is directed to the order in which the groups 

and the cations within the group are written. First the 

octahedral group, enclosed in parentheses, is written,

115
116 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

with the cations in that group noted in order of decreasing valence (except Ti, which is written after Al). Then 

the tetrahedral group, also enclosed in parentheses, is 

written, again with the cations noted in order of decreasing valence. Above each group the charge is 

written. After these two groups, which indicate the 

cationic composition of the layers, the anionic composition, Oi0 (OH,F) 2 , is written and the whole is bracketed, thus indicating the composition of the composite 

layer. After the upper part of the closing bracket, the 

total negative charge on the composite layer is noted. 

This is followed by a notation in parentheses of the interlayer cation content, with the positive charge carried 

by these cations written at the top of the closing 

parenthesis, and the total number of positions occupied 

by these cations written at the bottom. The interlayer 

cations are written last, rather than first, which is the 

more conventional position, because the amount and 

charge of the interlayer cations are dependent on and 

must neutralize the charge on the composite layer.

The negative charge on the composite layer and the 

positive charge on the interlayer cations should be close 

to 1.00 in the half-cell formula. In evaluating the 

dependability of the formulas used in this study a 

variation of plus or minus 0.10 was permitted in these 

values. Formulas in which the negative charge on the 

composite layer and the interlayer cationic charge were 

greater or less than 1.00 by more than 0.10 were not 

used in the study unless the number of sites occupied 

by the interlayer cations was less than 1.10. For 

example, in a few formulas the negative compositelayer charge and the interlayer cationic charge were 

greater than 1.10, but because of the presence of bivalent interlayer cations (Ca), the number of interlayer 

sites occupied was less than 1.10. Such formulas were 

included in the study. The analyses of aluminum 

lithium micas that were used in the study and data 

from which their calculated formulas can be written 

are given in table 6, in order of increasing lithium 

content, and analyses of the ferrous lithium micas used 

in the study, with data for writing their calculated 

formulas, are given in table 7.

Some analyses of ferrous lithium micas were not used 

in the study. In most of these analyses, which are 

given in table 8, the alkali content is high compared 

with the octahedral and tetrahedral cations; in the rest 

it is low. These discrepancies may be due to faulty 

analysis, particularly failure to determine lithium properly, or to nonhomogeneous or contaminated samples.

Any error in the Li determination has a double 

effect, as Li is an octahedral cation and the other 

alkalies are interlayer cations. If the Li is not completely separated, the part not separated is reported as 

Na; thus the Na reported is too high, the alkalies

calculated as interlayer cations are also too high, and 

the octahedral cations are too low. If the determination of Li errs on the high side, the other alkalies 

reported are too low, and the octahedral cations are 

too high. If the sample is not homogeneous, it is possible that the part taken for determination of the 

alkalies might be higher or lower in alkalies than the 

part taken for determining the other constituents, SiO2, 

A12O3 , Fe2O3 , and MgO.

ALUMINUM LITHIUM MICAS

INTERPRETATION OF COMPOSITION OF LEPIDOLITES BASED ON END MEMBERS

In recent years, following Stevens (1938) and 

Winchell (1942), there has been a strong tendency to 

interpret lepidolites as isomorphous mixtures of various 

end members. Stevens found that the composition of 

the 17 samples upon which he based his study closely 

approximates that of isomorphous mixtures of polylithionite,

with biotite,

R^o(Si3.ooAl1 .oo)010 (OH) 2K1 .o0)

lithium muscovite,

(Ali.6oLi 1 .5o)(Si3.ooAl1 .oo)Oio(OH) 2Fi.00,

and muscovite,

A12 .00 (Sis .00 Ali .00) Oj0 (OH) 2Kj .00,

Stevens considered that in such solid solutions the end 

members would not be present as individual endmember unit cells, but that the ions of which the end 

members are composed would be distributed uniformly 

throughout the structure. The selection of end members to interpret the composition of lepidolites is an 

arbitrary one. As Stevens (1938, p. 623) remarks:

Other combinations of four end members which express the 

compositions equally well are: polylithionite, zinnwaldite (assuming its formula to be K-LiR"Al-AlSi3OioF2), lithium muscovite, 

and muscovite; polylithionite, taeniolite (K-LiR2 "-Si4OioF2), lithium muscovite, and muscovite. In addition, 5 or 6 of the 

above end members may be taken, depending on what end 

members are used to express the bivalent ion content.

Winchell (1942) interpreted lepidolites as isomorphous mixtures of polylithionite, paucilithionite (identical with Stevens' lithium muscovite), and protolithionite (K2LiFe4Al3Si602oF4). He calculated 28 lithium 

micas to these end members and found that Li2O was 

deficient in all but 1 and that the average deficiency 

in Li2O was almost 1 percent by weight (0.91). However, if some muscovite was assumed to be present also, 

the deficiency in Li2O could be eliminated and the
INTERPRETATION OF LITHIUM MICAS 117

composition satisfactorily explained. Winchell considered muscovite to be present, not in solid solution 

but as a discrete mineral which might be so intimately 

intergrown or intermixed as to be difficult to detect 

optically.

Lepidolite and muscovite are, indeed, often intimately 

associated. In Stevens' study of lepidolites, five 

samples are discarded because small flakes of lepidolite 

in them were found to contain minute inclusions of 

muscovite. Winchell believed that muscovite may 

coexist with lepidolite in units too small to be detected 

optically. Ginzburg and Berkhin (1953) believe that 

considerable lepidolite in pegmatitic rocks has been 

derived from metasomatic replacement of muscovite 

and biotite. By incomplete replacement reactions, 

heterogeneous mixtures of the primary mica with 

lepidolite have been, they believe, analyzed as one mica 

type. Pale-violet lepidolites from muscovite in pegmatites from the Kalbinsk Chains, or from Turkestan, 

often contain relict inclusions of muscovite and intimate 

graphic intergrowths with this primary muscovite. 

However, the amount of muscovite that Winchell had 

to assume to be present to account for the deficiency 

in lithium content more than 10 percent in 20 out of 

28 samples is such that its presence could easily be 

detected by X-rays. For example, Stevens' sample 8 

(36, table 6), with an Li20 content of 5.11 percent, was 

estimated by Winchell to contain 29.9 percent muscovite. X-ray study by Hendricks and Jefferson (1939) 

of this sample showed it to have a one-layer lepidolite 

structure. They did not report the presence of any 

muscovite in this sample nor in any other of Stevens' 

samples that had more than 5 percent of Li2 0. They 

found, however, that Stevens' sample 1 (21, table 6), 

with a Li20 content of 2.70, was structurally a muscovite. They found samples 2-5 (22, 23, 24, and 29, 

table 6), too fine grained for study. Later study of 

X-ray and Weissenberg photographs by Levinson (1953) 

confirmed Hendricks and Jefferson's findings with 

respect to Stevens' samples. In addition Levinson 

showed that Stevens' samples 2-5 were mixtures of 

2-layer muscovite and 6-layer lepidolite. These studies 

of the crystal structure of lepidolites show that deficiency of Li in them, as compared with end members, 

cannot always be explained by assumption of admixture with muscovite. It is probable that some 

materials that have been analyzed as "lepidolites" have 

contained some occluded or interlayered muscovite, 

but the work of Hendricks and Jefferson and Levinson 

demonstrates that lepidolites have characteristic optical 

properties and structures, and that they are not mixtures of end members as interpreted by Winchell and 

Stevens.

COMPOSITIONAL CHANGES SHOWN BY THE 

ANALYSES

The analyses given in table 6 indicate a general 

increase in Si02 content, decrease in A12O3 content, 

decrease in H20+ content, and increase in F content 

with increase in Li20 content. Some of the analyses 

in which Li20 is very low have only 45 percent or even 

less of Si02 , as compared with Si02 contents of more 

than 55 percent in those in which Li2O is high. On 

the other hand, analyses which are very low in Li2O 

content have the highest amounts of Al, more than 35 

percent, whereas those highest in Li2O content are 

lowest in A1203 content, some having only 15 percent 

or even less. Similarly, analyses very low in Li2O 

content have a H20+ content of 4 percent or more but 

a low content of F, less than 0.5 percent, and analyses 

that contain high amounts of Li20 are very low in 

H20+, 0.5 percent or less, but have high contents of 

F, 8 percent or more. These relations are reflected in 

the data for the calculated formulas which are included 

in the table. These formulas indicate ailso that octahedral occupancy increases from about 2 sites in aluminum lithium micas very low in Li20 to about 3 sites 

in those containing the highest amounts of Li20. 

These, in general, orderly compositional variations 

accompanying increase in Li20 content suggest the 

sort of isomorphous substitution that characterizes 

other members of the mica group, such as the substitution of bivalent and other trivalent ions for aluminum 

in the muscovites (Foster, 1956) and the substitution of 

trivalent and other bivalent cations for magnesium in 

the phlogopites and biotites (Foster, 1960, p. 16-32). 

A similar replacement system among the aluminum 

lithium micas was suggested by Levinson (1953, p. 88) 

on the basis of his work on the structure of the micas.

HYPOTHETICAL LI-(OCTAHEDRAL AL) REPLACEMENT RATIOS

Theoretically, Li can be accommodated in muscovite 

micas in 4 different ways: occupancy of vacant octahedral sites, replacement of 1 ion of Al by 1 ion of 

Li, replacement of 1 ion of Al by 2 ions of Li, and 

replacement of 1 ion of Al by 3 ions of Li. The first 

3 methods of accommodation necessitate layer-charge 

readjustments, Li being univalent and Al trivalent; 

the fourth method does not, as the 3 positive charges 

carried by 3 Li ions exactly balance the 3 positive 

charges of the replaced Al ion. However, it does necessitate increase in octahedral occupany, as do also the 

first and third methods.

In attempting to explain a form of muscovite having 

as much as 3.3 percent of Li20, Levinson (1953, p. 93) 

speculated as to whether it is possible for such a large 

amount of Li to replace Al isomorphously in the
118 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

muscovite structure. He concluded that because of 

similarity in atomic radii, Al=1.43 A (angstrom units), 

Li=1.51 A, the substitution is possible but not necessary as Li could occupy vacant octahedral positions. 

The effect of this sort of accommodation of Li can be 

illustrated by Stevens' (1938, p. 615) sample 1 (21,

-0.15

2.00

table 6), which Levinson found to have a normal 

muscovite structure and which contains 2.70 percent of 

Li2O. This amount of Li2O is equivalent to 0.73 

octahedral positions in the calculated formula. If this 

number of vacant octahedral positions in the primary 

muscovite formula

-0.86

-1.00 T7- + 1.00 IM.OO .

which has the same bivalent-ion content as Stevens' sample, were to be occupied by Li, with no replacement 

of Al,

+0.58 -1.58

certain other changes in layer-charge relations and in 

the composition of the tetrahedral layer necessarily 

follow. The addition of 0.73 positive charges to the 

octahedral layer changes the negative charge of 0.15 

previously on that layer to a positive charge of 0.58. 

This positive charge on the octahedral layer requires 

an increase in the negative tetrahedral charge to 1.58, 

by increase in Al content and decrease in Si content, 

in order to preserve the total composite-layer charge 

at 1.00. Thus a lithium-containing muscovite in 

which Li merely occupies vacant octahedral positions 

would, in general, be characterized by a positive octahedral charge and a negative tetrahedral charge in 

excess of 1.00 by an amount equivalent to the positive 

octahedral charge, by a decrease in Si equivalent to the

increase in negative tetrahedral charge, and by a 1:1 

relation between the number of positions occupied by 

Li and the increase (above 2.00) in occupied octahedral 

positions. These characteristics are quite different 

from those shown by the calculated formulas. As 

illustrated in figures 26 and 28, particularly, the 

formulas exhibit an increase, not decrease, in Si content 

with increase in Li content, and an approximate 2:1 

ratio between the number of positions occupied by Li 

and the increase (above 2.00) in the number of octahedral sites occupied. The compositional and charge 

relations shown in these figures, therefore, indicate 

that Li is not accommodated in the structure by simple 

occupancy of vacant octahedral sites by Li. In the 

actual formula for Stevens' sample 1 (21, table 6)

-0.20 -0.84

247

the octahedral charge is negative, not positive, Si is 

greater than 3.00, not less, and the ratio of positions 

occupied by Li to the increase (above 2.00) in the 

number of octahedral sites occupied is about 5:3, not 

1:1. Furthermore, simple occupancy of vacant octahedral sites by Li, with no replacement of Al, cannot 

explain the amounts of Li found in many aluminum 

lithium micas. The limit of octahedral occupancy

-1.61

possible, 1.00 octahedral position, is equivalent to 

only about 3.75 percent of Li2O, whereas many aluminum lithium micas contain more than 5 percent of 

Li2O.

If the Li content of Steven's sample 1 is added to 

the primary mica above, in the replacement ratio of 1 

Li for 1 octahedral Al, the following irrational formula 

results:

0.00

2.00

The deficiency in positive charges in the octahedral 

layer is so great that the negative charge on the layer 

is 1.61, and, even with complete filling of the tetrahedral 

layer with Si, the charge on the composite layer is 

also 1.61, instead of 1.00. The greatest amount 

of Li that can substitute for octahedral Al, ion for ion,

in an ideal muscovite, and produce a rational formula, 

is 0.50:

-1.00 0.00

2.00

Any greater degree of substitution at this ratio results
INTERPRETATION OF LITHIUM MICAS 119

in too great a negative octahedral charge and compositelayer charge. This Li limit is too low to account for 

the composition of many aluminum lithium micas.

A 2:1 Li-(octahedral Al) replacement ratio for the 

amount of Li present in Stevens' sample 1 in the 

primary muscovite above results in a formula,

-0.50 -0.50

[(Al1 . 48Feo+3o 1 Feo+g2Mgo.ot Mn0t?2Lio. 73)(Si3. 5oAlo. 50)010 (OH,F) 2]- 1 - 00 K1^b00,

2.37

which resembles more closely the characteristics of the 

calculated formulas as illustrated in figures 25, 26, and 

28; namely, a decrease in Al (IV) content, increase in Si 

content, and an increase in total octahedral positions 

occupied which is about one-half the number of lithium 

positions occupied. The end member for this ratio of 

replacement would have the formula,

-i.oo o.oo

[(Al1 .ooLi2 . 00)Si4010 (OH,F) 2]- 1 - (W K1+Jb00.

3.00

In this formula the ratio of positions occupied by Li to 

the increase in octahedral positions occupied is 2:1, 

the increase in Si is also equivalent to half the increase 

in Li, and the decrease in total Al is equivalent to the

increase in Li. These changes can be expressed in the 

equation

0.5 Si + 0.5 nOct.Site=nAl. (A)

. .

[(Al1 . fioFe0^iFeot§2Mg0. 01Mn0tf2Li0 . 73)(Si3. 1 4Al0 . 86)010 (QH,F)2

This ratio of replacement permits the admission of 

enough Li into the structure to account for the composition of the highest amounts of Li that have been 

reported in lepidolites. This formula represents the 

composition of polylithionite, one of the Li end members used by both Stevens and Winchell in their 

interpretation of the composition of lepidolites.

Substitution of 3 Li cations for 1 octahedral Al in the 

primary muscovite for Stevens' sample 1 produces a 

formula,

-1.00

which is very close to that calculated from the analysis 

of this sample, suggesting that the Li-(octahedral Al) 

replacement ratio for this sample is very close to 3:1. 

The end-member formula for this ratio of replacement,

o.oo -i.oo

[(Al1 . 50Li1 . 50)(Si3 .ooAl1 .oo)01 o(OH,F)2]- 1 - 00 K1H:ob00)

3.00

has the same tetrahedral group as muscovite. As 1.5 

cations carrying 1.5 positive charges replace 0.5 cation 

of Al, which also carries 1.5 positive charges, there is 

no change in layer-charge relations. The compositional changes involved in this ratio of replacement of 

Li for octahedral Al may be expressed as

.5nLi + nOct.Site=0.5nAl (B)

Stevens called this hypothetical end member lithium 

muscovite and Winchell called it paucilithionite. 

Neither name is satisfactory. Muscovite is a heptaphyllic or dioctahedral mica, whereas the above formula 

is that of an octaphyllic or trioctahedral mica. Winchell used the prefix pauci because the formula represents 

the minimum tenor of Li in a lepidolite end member. 

However, the use of this prefix, which means small or 

little, for an end member containing more than 5 percent of Li2O, and in which one-half of the available 

octahedral sites are occupied by Li, too much minimizes its lithian character. The prefix also exaggerates 

the difference between this hypothetical end member

and polylithionite, which contains about 7.5 percent 

Li and in which two-thirds of the octahedral sites are 

occupied by Li. The three Li ions occupying octahedral sites in the unit-cell formula,

0.00 -2.00

[ (A13 . 03.00) (Sis. op Al2 .oo)Q2o(OH,F) 4]

"

~ 2'

6JDO

suggests the name "trilithionite" as more appropriate 

for this hypothetical end member. This name also 

suggests the 3:1 Li- (octahedral Al) replacement ratio 

of this end member.

This discussion of the possible methods of accommodating Li in the muscovite structure shows that simple 

occupancy of vacant octahedral sites in muscovite by 

li or replacement of 1 octahedral Al by 1 Li either 

produce irrational formulas for end members or produce end-member formulas whose Li content is too low 

to be applicable to the interpretation of the composition of some lepidolites. Replacement of octahedral 

Al by Li in the ratio of 2 or 3 for 1 produces rational 

end-member formulas capable of interpreting the 

composition of these micas.

RELATION OF LI TO OTHER CONSTITUENTS IN CALCULATED FORMULAS

RELATION BETWEEN LI AND OCTAHEDRAL AL

The relation between the number of octahedral positions occupied by Li and the number of octahedral

54879C
120 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

positions assumed to have been vacated by Al in 

formulas of analyzed aluminum lithium micas is shown 

in figure 25. In a study of the dioctahedral micas 

(Foster, 1956) it was found that octahedral occupancy 

in these micas is always close to 2.00 and that replacement of Al by other trivalent and by bivalent cations is 

ion for ion. Consequently, in calculating the number 

of octahedral-Al positions replaced by Li it was assumed 

that 2.00 octahedral sites were occupied in the primary 

muscovite, and that replacement of octahedral Al by 

Fe+3 , Fe+2, Mg, and Mn was ion for ion such as 1 ion 

of Fe+3 for 1 of Al, 1 of Fe+? for 1 of Al. The difference, 

then, between 2.00 and the number of octahedral sites 

occupied by Al and these other octahedral cations is 

assumed to represent the number of octahedral-Al 

cations replaced by the Li present. All but a few of 

the points fall between line B, which represents the 

2:1 Li-(octahedral Al) replacement ratio and leads to 

the end member polylithionite, and line C, which 

represents the 3:1 Li-(octahedral Al) replacement ratio 

and leads to the end member trilithiouite.

In the formulas represented by points lying between 

these 2 lines, therefore, the Li-(octahedral Al) replacement ratio is between 2 and 3. The location of the 

points indicates that in most of the formulas the ratio 

is between 2.3 and 2.8. Only 1 of the formulas represented by points that fall outside the area embraced 

between lines B and C contains more than 2.0 percent 

Li2O. This formula, in which the Li-(octahedral Al)

replacement ratio is 1.9, is closest in composition to 

the end member, polylithionite. The other points that 

fall outside the area between lines B and C fall below 

line C, indicating that in the formulas that they 

represent, the Li-(octahedral Al) replacement ratio is 

greater than 3. In most of these formulas, however, the 

ratio is quite close to 3, and the discrepancy may be 

due to slight analytical error, particularly in the determination of Li2O, to lack of homogeneity in the sample, 

or to error in assuming that the octahedral occupancy in 

the primary muscovite was exactly 2.00 in calculating 

the number of Al sites replaced. The amount of 

replaced Al in these formulas is so small that an error 

in octahedral occupancy in the primary muscovite of as 

little as 0.03 less than 2.00 could account for the high 

Li-(octahedral Al) ratio in them.

It has been shown that accommodation of Li by 

replacement of octahedral Al in the ratio of 2 for 1 

involves compositional changes in accordance with 

equation A, wLi + 0.5/iSi+0.5riOct.Site==nAl. In other 

words, for each ion of Li or fraction thereof added, 

half as many Si ions are added and half as many additional octahedral sites are occupied, but the loss in 

total Al ions (octahedral and tetrahedral) is the same 

as the gain in Li ions. It was also shown that in accommodation of Li by replacement of octahedral Al in the 

ratio of 3.0 for 1.0 involves compositional changes in 

accordance with equation B, 1.5/iLi-f nOct.Site= 

O.SnAl. Thus for each 1.5 ion of Li or fraction thereof

1.00

0.00

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

OCTAHEDRAL SITES OCCUPIED BY Li

1.60 1.80 2.00

FIGURE 25. Relation between octahedral sites occupied by Li and vacated by Al in aluminum lithium micas.
INTERPRETATION OF LITHIUM MICAS 121

added, two-thirds as many octahedral sites are occupied 

and there is a loss in octahedral Al ions equivalent to 

one-third the gain in Li ions. This manner of adjustment involves no change in Si content. As the Li- 

(octahedral Al) replacement ratios in the analyses 

studied are, for the most part, between 2 and 3, it would 

be expected that they would show compositional changes 

between those specified by equations A and B, and that 

the closer the replacement ratio in any particular 

formula is to 2 or 3, the closer the compositional changes 

indicated by that formula will be to equation A or 

B, respectively.

RELATION BETWEEN (LI-R«) AND 81

The relation between (Li R+2) and Si in the aluminum lithium micas studied is shown in figure 26. If, 

except for Li, the octahedral layer were entirely occupied by trivalent ions, Li in the formulas would 

have been plotted directly against the increase (above 

3.0) in Si. However, the octahedral groups in the 

formulas are not made up entirely of trivalent ions 

plus Li, but also contain varying amounts of bivalent 

ions, and some of the positive charges carried by Li 

compensate for the deficiency in charge, compared with 

Al, of these ions. For example, in the formula for 

analysis 34, table 6,

-0.41 -0.62

[(Al 1 . 29Feo.+o?Mnot?8Li1 . 38)(Si3. 38Al0 . 62 )01 o(OH,F)oJ- 1 - 03K(Na) Rb,Cs) 1+^°3 ,

2.84

0.17 of the positive charges carried by Li compensate 

for the deficiency of the number of positive charges 

present in the octahedral layer compared with the 

number carried by the same number of trivalent ions. 

The effect on the Si content is as though 1.21 and not 

1.38 ions of Li were present. In order to eliminate the 

effect of the variable amounts of R+2 ions present in 

the formulas, Si is plotted against (Li R+2 ) in figure 

26, not against Li alone. In some of the formulas in 

which Li is very low, the positive charges added by 

Li do not entirely compensate for the deficiency in 

octahedral charge due to the bivalent ions present.

In figure 26 all but a few of the points representing 

the (Li R+2):Si relation in the formulas fall between

4.00

^3.80

line A, which represents the 2:1 Li:Si relation found 

in formulas in which the Li-(octahedral Al) replacement ratio is 2, and line B, the baseline, which represents 

the 1.5:0 Li :Si relation found in formulas in which 

the Li-(octahedral Al) replacement ratio is 3. Thus 

the (Li R+2):Si relation in most of the formulas is 

consistent with that to be expected in formulas for 

aluminum lithium micas in which the Li-(octahedral 

Al) replacement ratio is between 2 and 3.

RELATION BETWEEN LI AND TOTAL AL

The relation between the number of octahedral sites 

occupied by Li and the total number of formula sites 

occupied by Al is shown in figure 27. Except for some

3.60

3.40

3.20

3.00 B Theo'etical 1.5:0 ratio Li:Si

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 

OCTAHEDRAL SITES OCCUPIED BY(Li-R+2 )

1.60 1.80 2.00

FIGURE 26. Relation between (Li R+2 ) and Si in aluminum lithinm micas.
122

3.00

2.60

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

2.20

1.80

en 

O

1.40

1.00

0.60

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60

FORMULA POSITIONS OCCUPIED BY Li 

FIOUKK 27. Relation between the number of formula sites occupied by Li and R+3 in aluminum lithium micas.

1.80 2.00

points representing formulas with a low content of 

Li, almost all the points representing the Li:Al relation 

in the calculated formulas of the analyses studied fall 

between lines A and B. Line A represents the Li:Al 

relation, as compared with muscovite, in formulas in 

which the Li-Al replacement ratio is 3.0; line B represents the LirAl relation when the Li-Al replacement 

ratio is 1.0. The location of most of the points, therefore, indicates a decrease in Al with increase in Li 

that is in accordance with the Li:Al relation to be 

expected in formulas in which the Li-Al replacement 

ratio is between 2 and 3.

RELATION BETWEEN LI AND OCCUPIED OCTAHEDRAL SITES 

IN EXCESS OF 2.00

The relation between Li and the number of octahedral 

sites occupied in excess of 2.00 is shown in figure 28. 

In aluminum lithium micas in which the Li-(octahedral 

Al) replacement ratio is 2, the number of octahedral 

positions occupied in excess of 2.00 is theoretically onehalf the number of octahedral positions occupied, as 

represented by line B (fig. 28); in aluminum lithium 

micas in which the Li-(octahedral Al) replacement ratio 

is 3, the number of octahedral positions occupied in excess of 2.00 is theoretically in the ratio of 1.5 Li to 1.0 

octahedral position, as represented by line A (fig. 28). 

In accordance with the Li-(octahedral Al) replacement

ratios found in the calculated formulas, most of the 

points representing the relation between the number 

of octahedral sites occupied by Li and the total number 

of octahedral sites occupied in excess of 2.00 fall between the two lines.

RELATION BETWEEN LlaO AND F

A casual inspection of the Li2O and F values in the 

analyses in table 6 shows a general increase in F content with increase in Li2O content. The grouping of 

the points in figure 29 along the line representing a 

1:1 ratio between Li2O and F indicates a tendency toward a 1:1 relation in these constituents in aluminum 

lithium micas. Considering the difficulties inherent in 

the determination of both Li2O and F, some of the discrepancies shown in figure 29 are probably more to be 

attributed to error in determination than to other than 

a 1:1 relation between Li2O and F. Increase in F content is accompanied by decrease in H2O-f content 

(fig. 30).

RELATION BETWEEN LI20 CONTENT, OCTAHEDRAL 

OCCUPANCY, AND STRUCTURE

The variations in composition accompanying increase 

in Li content shown in figures 25, 26, 27, and 28 are 

those to be expected if Li were substituted for octahedral
INTERPRETATION OF LITHIUM MICAS 123

3.00

2.00

0.00 0.20 0.40 0.60 0.80 1.00 1.20 

OCTAHEDRAL SITES OCCUPIED BY Li

1.40 1.60 1.80 2.00

FIGURE 28. Relation between Li and octahedral occupancy in excess of 2.00 in aluminum lithium micas.

0.40 

tn

CO

<

z

< 0.30 

£ 

u.

u_ 

O

£0.20

U)

<

5 

o

u) 

0.10

0.00 

0.

Fi

Al ini 

locta 

resem 

with i 

occup 

lepido

Theoretical

. 

** / 

# . 1

Li ratio Li 20

/

1 

t

 +

f

 

 

.- -

:4#

J^r '

/i S

9 

/. '

00 0.10 0.20 0.30 0.40 0.50 

EQUIVALENT OF Li 2 0 BY ANALYSIS

 JURE 29. Relation between LijO and F in aluminum lithium micas.

nuscovite in ratios varying between 2 and 3 Li for 

icdral Al. Compositionally, therefore, these micas 

ble members of an isomorphous series that starts 

muscovite. However, the increase in octahedral 

ancy from 2.00 in muscovite to 3.00 in some 

lites and in the theoretical end members, poly6.0

5-0

(- 

5 4.0

0

o:

LJ 

Q.

Z

9, 3-° x1

2.0 

1.0

°-°c

FlGU

» «

» 

« 

<?

 

.«

 

 

e

 

a

«

e

 

 <

 

» 

9

% 

*% 

a

 

e

8

* 

e

2 4 6 8 1C

F, IN PERCENT

RK 30. Relation between F and HjO+ in aluminum lithium micas.
124 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

lithionite and trilithionite, raises the problem of structural continuity.

Information as to the structure of aluminum lithium 

micas is furnished by Hendricks and Jefferson's study of 

Stevens' lepidolite samples (1939, p. 761), and by 

Levinson's study of aluminum lithium micas (1953) 

that varied in Li2O content from a few tenths of a 

percent to more than 7 percent. Included among the 

micas studied by Levinson were most of Stevens' 

samples. Except for a few samples in a restricted 

range of Li2O content, both investigators found that the 

mica samples studied were not mixtures, as postulated 

by Stevens (1938) and Winchell (1942), but that each 

consisted of one structural form. Hendricks and 

Jefferson found that Stevens' sample 1 (21, table 6), 

which has an Li2O content of 2.70 percent, has a muscovite structure, but that his samples 6-10 and 12-17, 

which contain between 5.04 and 7.26 percent Li2O, all 

have lepidolite structures. Also, samples 2-5 of 

Stevens' suite, which contain between 3.51 and 3.96 

percent Li2O and fall, in Li2O content, between sample 

1, with a muscovite structure, and 6, with a lepidolite 

structure, were too fine grained for the type of study 

made by them. Levinson (1953, p. 99) speculated that 

it seemed likely that "* * * these fine-grained micas 

owe their macrostructural defects to small-scale variations in their crystal structure which itself probably is 

assignable to their chemically transitional position in 

the muscovite-lepidolite series." In order to test this 

hypothesis, he made detailed powder X-ray studies of 

these fine-grained micas and found that they all are 

combinations of 2-layer muscovite and 6-layer lepidolite 

forms, with the 6-layer l lepidolite form predominating 

over the 2-layer muscovite form in all the samples. As 

a result of his study of the aluminum lithium micas, 

Levinson concluded that micas with less than 3.3 percent Li2O have muscovite structure; those with 3.4 to 

4.0 percent Li2O have mixed structures, and that those 

with more than 4.0 percent Li2O have lepidolite 

structure.

Data for correlation of structure with the number of 

sites occupied by Li and octahedral cations in Stevens' 

samples are given in table 1. These data show that in 

the half-cell formula for Stevens' sample 1, which has 

a muscovite structure, octahedral occupancy is 2.47; 

in Stevens' 2, 3, 4, and 5, which are combinations of 

muscovite and lepidolite forms, octahedral occupancy 

is 2.50 to 2.62 sites; and in Stevens' other samples, all 

of which have lepidolite structures, octahedral occupancy is greater than 2.70. Thus the samples that are 

combinations of forms, giving evidence of transition in 

structural type, have octahedral occupancies about 

halfway between 2.00 and 3.00. In these samples, Li

i Smith and Yoder (1956, p. 215) renamed this 2M».

Stevens (1938)

Specimen

1 __ ...

2_ 

3.. ..

4 .....

5.. __ -.

6 ....

7..-. ...

8. _ ......

9

10 

11..... _ .

12- 

13.. _ ....

14 - -.

16 

16 .

17. -

Li8O 

(percent)

2.70 

3.51

3.70 

3.81 

3.96 

5.04

5.05 

5.11 

5.33

5.39 

5.51 

5.64 

5.78 

5.89 

6.18 

6.84 

7.26

LI

sites

0.73 

.94

1.00 

1.01 

1.06 

1.35

1.38 

1.35 

1.44 

1.50 

1.49 

1.52 

1.56 

1.61 

1.68 

1.84 

1.93

Octahedral occupancy

2.47 

2.50

2.59 

2.57 

2.62 

2.72

2.84 

2.73 

2.79 

2.93 

2.84 

2.85 

2.90 

2.92 

2.94 

2.96 

2.93

Structure

Hendrieks and 

Jefferson (1939)

Too fine grained 

for study.

- do.. _

 .do.. 

6-layer monoclinie. 

 -do 

__ do _ ____

 .do... 

Not available... -- 

6-layer monoclinie.

3-layer hexagonal.

.....do. __ .... _ .

 .do.. 

Levinson (1953)

Normal museovite. 

6-layer lepidolite and 

2-layer museovite. 

Do. 

Do. 

Do. 

6-layer monoelinie 

(and lithian museovite). 

Not available. 

1-layer. 

Not available. 

Do. 

Do. 

Do. 

1-layer. 

3-layer hexagonal. 

1-layer. 

Do. 

Do.

occupancy is close to one octahedral site. These relations between Li occupancy, octahedral occupancy, and 

structural type in Stevens' and Berggren's samples, 

which were also included in Levinson's study, are shown 

graphically in figure 31.

TABLE 1. Relation between Li,O content, octahedral occupancy, 

and structure of lithium micas analyzed by Stevens

Just as the transitional samples consist of a combination of forms, the values reported for various constituents on analysis are composite values made up of 

the amounts of these constituents contributed by muscovite and lepidolite forms present. For example, the 

value for Li2O found on analysis in these samples is a 

composite value made up of Li2O contributed by the 

muscovite present, in which the Li2O content may be 

less than 3.0 percent, and of Li2O contributed by the 

lepidolite present, in which the Li2O content may be 

more than 4.0 percent. Thus the Li2O values in the 

area of mixed forms which suggest a continuity in Li 

content in figure 31, for example, between ahiminian 

lithium micas of muscovite structure and those of lepidolite structure are deceptive, and there is actually a 

gap in Li content between these two types of aluminum 

lithium micas. Similarly, all the other analytical values 

reported for these mixed-form samples are composite 

values. Therefore, both the compositional and structural continuity of the aluminum lithium series is broken 

at the point at which change in structure takes place, 

and the isomorphous series that starts with muscovite 

extends only to an octahedral occupancy of about 2.45 

sites and an Li occupancy just short of 1.00 octahedral 

site.

Following Schaller (1930), these aluminum lithium 

micas having muscovite structures are termed "lithian" muscovites. Levinson applied this term to a 

new variation of the muscovite polymorph which he 

observed in muscovite containing at least 3.3 percent
INTERPRETATION OF LITHIUM MICAS 

Muscovite structure Mixed forms Lepidolite structure

125

3.00

02.80

-2.60 

o

uj

Q. 

O

8

w2.40

2.20

2.00

10

13

12

16

17

EXPLANATION

Stevens' samples (1938)

Berggren's samples (1940-41)

Indefinite boundary

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

OCTAHEDRAL SITES OCCUPIED BY Li

1.60 1.80 2.00

FIGURE 31. Relation between Li occupancy, octahedral occupancy, and structural type in Stevens' and Berggren's samples. (Numbers refer to samples ol Stevens, 1938;

letters refer to samples of Berggren, 1940, 1941.)

Li2O and possibly as much as 4.3 percent Li2O. In 

so doing he applied a chemical term to a structural 

variation, whereas Schaller had proposed the use of 

the adjectival ending "ian" to names of chemical elements to describe a variety in which there was minor 

and variable replacement of an essential element by 

an analogous element, as chromian muscovite, or vanadian muscovite. According to this usage a lithian 

muscovite is a muscovite containing some Li in place 

of Al, not a muscovite having a slight structural variation over a limited range of Li2O content, as used 

by Levinson.

Because of their different structure, and the break 

in compositional continuity in the transition area, the 

lepidolites do not belong to the aluminum lithium isomorphous series that starts with muscovite. However, 

in composition they can be interpreted as if they were 

a continuation of this series, that is, on the basis of 

Li replacement of octahedral Al in muscovite in ratios 

varying between 2 and 3 Li for 1 octahedral Al. This 

continuation in type and order of replacement beyond 

the structural transition zone is illustrated in figures 

25 through 31.

Available information on Li content and octahedral 

occupancy, Li-(octahedral Al) replacement ratios, and 

structure in Stevens' samples and in Berggren's samples that were studied by Levinson, listed in table 2, 

shows no consistent correlation between replacement

ratio and structure in lithian inuscovites and lepidolites. Lithian muscovites have Li-(octahedral Al) replacement ratios ranging from 1.5 to 2.9; lepidolites 

with 6-layer structures have Li-(octahedral Al) replacement ratios ranging from 2.1 to 2.8, and those with 

1-layer structures have Li-(octahedral Al) replacement 

ratios ranging from 1.9 to 2.6. Apparently, therefore, 

micas in which the Li-(octahedral Al) replacement ratio 

is 2 are not distinct structurally from micas in which 

this replacement ratio is 3.

Three polymorphic variations were found among the 

lepidolites: the 6-layer monoclinic, the 1-layer, and the 

3-layer hexagonal. Levinson correlated the 6-layer 

monoclinic polymorph with lepidolites containing 4.0 

to 5.1 percent Li2O (equivalent to about 1.05 to 1.40 

octahedral sites in half-cell formulas), arid the 1-layer 

polymorph with those having more than 5.1 percent 

Li2O. However, Hendricks and Jefferson (1939) concluded that there is no apparent correlation between 

the different lepidolite polymorphs and composition. 

Thus Stevens' sample 12 (47, table 6), with 5.64 percent Li2O, has a 6-layer monoclinic structure whereas 

others with lower Li2O content (table 1) have 1-layer 

lepidolite structures. Nor is there, apparently, any 

relation among lepidolites, between octahedral occupancy and the different lepidolite polymorphs. As 

shown in table 2, octahedral occupancy in the 6-layer 

lepidolites studied ranges between 2.72 and 2.96; that
126 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

in the 1-layer lepidolites ranges between 2.73 and 2.96. 

Hendricks and Jefferson also found that the 6-layer and 

1-layer polymorphs cannot be distinguished optically.

TABLE 2. Comparison of Li occupancy, Li-(octahedral Al) 

replacement ratio, and structure

Sample

Table6

11.. _ .

13 

15 

16 

19- _ -

20 

21 

33 

34 

47 

53 

36 

39 

42 

50. __ . 

54 . 

57 

58 

Other reports

Identification

H 

J

F 

L 

E 

D 

1 

6

7 

12 

A 

8 

9 

10 

13 

15 

16 

17

Author

Berggren, 1940. . 

Berggren, 1941 .. 

Berggren, 1940. . 

Berggren, 1941.. 

Berggren, 1940- - 

__ do __ . ...

Stevens, 1938 __ 

__ do 

__ .do _ 

do.

Berggren, 1940- . 

Stevens. 1938 .... 

do

 ..do 

- do 

 - .do ... ...

 ..do 

 do 

Li2 0

(percent)

0.69 

.76 

1.10 

1.1 

1.8 

2.45 

2.70 

5.04

5.05 

5.64 

5.95 

5.11 

5.33 

5.39 

5.78 

6.18 

6.84 

7.26

Li

sites

0.18 

.20 

.29 

.30 

.48 

.66 

.73 

1.35

1.38 

1.52 

1.59 

1.35 

1.44 

1.50 

1.56 

1.68 

1.84 

1.93

Octahedral 

occupancy

2.06 

2.10 

2.16 

2.17 

2.31 

2.43 

2.47 

2.72

2.84 

2.85 

2.96 

2.73 

2.79 

2.93 

2.90 

2.94 

2.96 

2.93

Replacement 

ratio

1.5 

2.0 

2.3 

2.3 

2.8 

2.9 

2.8 

2.1

2.6 

2.3 

2.5 

2.2 

2.3 

2.6 

2.4 

2.3 

2.1 

1.9

Structure

Muscovite. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

6-layer and 

muscovite. 

6-layer. 

Do. 

Do. 

1-layer. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do.

DISCUSSION

On the basis of chemical evidence alone, the aluminum 

lithium micas can be considered as if they were members 

of an isomorphous series, starting with muscovite, in 

which Li replaces octahedral Al in the ratio of from 2 to 

3 Li for 1 octahedral Al. However, structural evidence 

indicates that the series is not continuous, either structurally or compositionally, but is broken about halfway 

between muscovite and polylithionite in a zone in which

octahedral occupancy is about 2.50 to 2.60 sites and Li 

occupancy is about 0.95 to 1.05 sites. In this zone the 

samples are mixed structural forms, muscovite and 

lepidolite, whereas samples with octahedral occupancy 

less than 2.50 sites or greater than 2.60 sites are 1 

structural form only. As the samples in this zone are 

mixtures of forms, the analytical values which suggest 

continuity in composition are composite values and do 

not actually represent the composition of single-form 

aluminum lithium micas having an octahedral occupancy of between 2.50 and 2.60 sites. Consequently, 

the compositional continuity is broken. The aluminum 

lithium micas, therefore, are members of 2 related 

series: the lithian muscovite series, which starts with 

muscovite and extends to micas having an Li occupancy 

of about 0.85 octahedral sites and an octahedral 

occupancy of about 2.50 sites, and the lepidolite series, 

which starts with a lepidolite having an Li occupancy 

of about 1.10 octahedral sites and an octahedral occupancy of about 2.65 sites and extends to a lepidolite 

having an Li occupancy of from 1.80 or more octahedral 

sites and an octahedral occupancy of about 3,00 sites. 

Selected formulas are given in table 3 that show the 

relation of lithian muscovites and lepidolites. This 

relation is shown graphically by histograms in figure 32. 

The chemical composition of both the lithian muscovites and lepidolites can be interpreted in the same 

way; that is, as if they were derived from muscovite 

by the replacement of octahedral aluminum by lithium 

in a ratio varying between 2 and 3 Li for 1 octahedral. 

The other compositional changes that characterize

TABLE 3. Selected formulas illustrating relation between lithian muscovites and lepidolites

Number in table 6

-0.04 -1.00

Formula

Li-(octahedral Al) 

replacement ratio

Lithian muscovites2o

-0.18 -0.87

2.17

21

-0.20 -0.84

[(AlKS8Feo+ g1 Feo+oiMgroiMno+ f2Li 0 . 70(Si3 . 16Alo. 84)01 o(OH)2]- 1 - 04(K,Na,Rb,Cs) + hgi

2.47

.2.8

Mixed

structural

forms

-0.41 -0.62.

-0.52 -0.52.

292 

-0.87 0.17
INTERPRETATION OF LTTHItTM MICAS 

Lithian museovites Mixed forms

127

Lepidolites

4.00

EXPLANATION 

ED

Li Octahed- Si Octahedral Indefinite 

ral Al occupancy boundary

0.00

SAMPLE 

32. Histograms of selected formulas showing the relation of lithian museovites and lepidolites. (Numbers below histograms refer to analyses in table 7.)

these micas increase in silica and decrease in the 

tetrahedral Al with increase in Li content are necessitated by the disparity in positive charges carried by 

the replacing Li and replaced octahedral Al.

The interpretation of the composition of these micas 

postulated by Stevens (1938) and Winchell (1942), as 

mixtures of end members, is not borne out by the structural work of Hendricks and Jefferson (1939) and 

Levinson (1953).

The relation between Li, R+2 (Fe+2,Mn+2,Mg), and 

octahedral R+3 (Al,Fe+3)-f Ti+* is shown in figure 33, in 

which the percentages of occupied octahedral sites 

occupied by Li, R+2 (Fe+2,Mn+2,Mg), and octahedral 

R+3 (Al,Fe+3)+Ti+* in each formula are plotted on a 

triangular diagram. In this diagram ideal muscovite 

falls at the lower left corner, which represents 100-percent occupancy of the octahedral layer by Al(+Fe+3 ), 

trilithionite is represented by a point midway along the 

left side of the triangle, and polylithionite is represented 

by a point two-thirds of the way up the left side of the 

triangle. The points representing octahedral occupancy of the calculated formulas of lithian museovites 

and lepidolites are distributed along the left side of the 

triangle from the lower left corner, which represents 

muscovite, to the point representing polylithionite. 

Because of the small amounts of FeO, MnO, and (or) 

MgO found in most lepidolites, few of these points fall 

on the outside boundary, as do trilithionite and polylithionite. However, all fall between the outside boundary and the line representing 10 percent of bivalent 

octahedral cations, Fe+2, Mn+2, and Mg.

FERROUS LITHIUM MICAS 

PREVIOUS INTERPRETATIONS OF COMPOSITION

Both Kunitz (1924, p. 409) and WiricheU (1927, p. 

274) regarded lepidolite and protolithionite as end members of a series characterized by decrease in Li content 

and increase in Fe+2, with protolithionite representing 

the Fe+2-high, Li-free end of the series. Intermediate 

members were known as zinnwaldites. Kunitz believed 

that lepidolite, KH2Al2Le(SiO4) 3 , contained a special 

group (2Li,Si), denoted as Le, that was completely 

replaceable by 3Fe+2 to form protolithionite. Winchell 

considered that lepidolite was miscible in all proportions 

with protolithionite in the crystal state, and that the 

natural lepidolites, zinnwaldites, and protolithionites 

were made up of various proportions of the end members. He regarded cryophyllite, a lithium mica described by Cooke (1867) from Cape Ann, Mass., as 

doubtful. At that time Winchell considered these 

minerals heptaphyllites, but later (1942, p. 117) he 

recognized them as octaphyllites and, furthermore, 

included some lithium in his formula for protolithionite.

Hallimond (1925, p. 311) also believed that lepidolite, 

zinnwaldite, and protolithionite form a series. However, as indicated by his formulas, RsO-LiaO^AlaCV 

6SiO3 -2H2O, for lepidolite, and K2O.Li2O.3RO-2AlaO3- 

6SiO2 -2H2O, for protolithionite, this series is 

characterized merely by addition of RO, the Li2O 

content remaining constant. Thus Hallimond's series 

was not a replacement series. The two zinnwaldites 

reported by Dana, he states, might be regarded as

548796 60 3
128 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

EXPLANATION

* 

Ideal end members

x 

Aluminum lithium micas

o

Aluminum lithium micas whose 

structure has been studied

Indefinite boundary

Lepidolites//; o

o 

>o x x

Lithian muscovites

T , *,_ * Trilithionite*ovx 0 x /x xx

Mixed forms//£o x x

Octahedral R+ 3 (Al, Fe +3)+Ti+4 R +2 (Fe+ 2 ,Mn,Mg)

FIGTTEE 33. Relation between Li, R-"-2(Fe-"-2,Mn+8,Mg), and octahedral R«(Al,Fe+3)+Ti-n in aluminum lithium micas.

consisting chiefly of the compound K2O-Li2O-RO 

2Al2O3 -6SiO2 -2H2O or, alternately, as mixtures of 

lepidolite and protolithionite. He believed that eryophyllite bears the same relation to lepidolite that 

phengite bears to muscovite.

A classification by Ginzburg and Berkhin (1953) includes the ferrous lithium micas as part of a series of 

which lepidolite is the high-Li end member and biotite 

is the Li-free end member. In this series the transition 

from biotite to lepidolite is supposed to be marked by 

the replacement of 2Mg+2 by Li and Al+3 .

Thus four kinds of series have been proposed to interpret the composition and relation of the ferrous lithium 

micas: the lepidolite-protolithionite series of Kunitz 

(1924, p. 409), in which the Le group (2Li,Si) is completely replaced by 3Fe+2 ; the lepidolite-protolithionite 

series of Winchell, in which the end members are miscible in all proportions and form intermediate members; 

the lepidolite-protolithionite series of Hallimond, in 

which Fe+2 is additive but Li remains constant; and 

the biotite-lepidolite series of Ginzburg and Berkhin, 

in which 2Mg is replaced by (Li+Al). In none of these 

series are the limits in composition between lepidolite, 

cryophyllite, zinnwaldite, and protolithionite defined. 

The clearest definition of the limits of composition 

between protolithionite, zinnwaldite, and cryophyllite 

is that stated in Hey (1955, p. 208). Hey gives the 

same formula 2[K2 (Li,Fe+2 ,Al) 6 (Si,Al) 8O20 (F,OH) 4] for 

all three, excepting only that Fe+3 is included in the 

(Li,Fe+2,Al) group in his formulas for protolithionite 

and cryophyllite, but he qualifies the formulas by observations on the amounts of Li, Fe+2, and Si typically 

present. Thus in protolithionite, zinnwaldite, and 

cryophyllite, Li occupies 1-2, «2, and «2^ formula
INTERPRETATION OF LITHIUM MICAS 129

positions, respectively; Fe occupies «!%, «1& and 

«1 (including Fe+3) formula positions, respectively; 

and Si 5%-6, «6X, and «7 formula positions, respectively. Following Dana (1892, p. 626), Hey gives zinnwaldite species status, with protolithionite and cryophyllite being considered varieties of zinnwaldite.

COMPOSITIONAL CHANGES SHOWN BY ANALYSES

The analyses of ferrous lithium micas vary considerably in SiO2 and A12O3 content, although there is a 

general increase in SiO2 content and decrease in A12O3 

content with increase in Li2O content. However, these 

relations are not as consistent as in the aluminum 

lithium micas. The Fe2O3 content is quite variable in 

ferrous lithium micas having less than 3.5 percent of 

Li2O; in ferrous lithium micas having more than 3.5 

percent of Li2O, Fe2O3 is generally low or absent. 

FeO is also quite variable, but, in general, decreases 

with increase in Li2O content. All but 1 of the ferrous 

lithium micas included in the study that contained less 

than 2 percent of Li2O have more than 15 percent of 

FeO, those with between 2.0 and 3.0 percent of Li2O 

have between 9.0 and 14.0 percent of FeO, and those

with more than 3 percent of Li2O have between 6.0 and 

12.6 percent of FeO. MgO is generally low. Many 

of the analyses contain less than 0.5 percent, and few 

contain more than 1.0 percent. Only 1 analysis has a 

significant amount, 5.23 percent.

In most of the formulas calculated from the analyses 

the number of octahedral sites occupied is greater than 

2.60. These micas are, therefore, trioctahedral or 

octaphyllic micas, not heptaphyllic micas as was 

formerly assumed by Winchell (1927, p. 274).

RELATION BETWEEN FERROUS LITHIUM MICAS, 

SIDEBOPHYLLITES, AND ALUMINIAN LEPIDOMELANES

In their principal compositional characteristics, 

their low MgO content with high FeO content, their 

octahedral occupancy, and their octahedral-tetrahedral 

charge relations, the ferrous lithium micas with low 

Li2O content resemble siderophyllites and lepidomelanes, which are the low-Mg members of the phlogopitebiotite-siderophyllite (or lepidomelane) Mg replacement 

system (Foster, 1960, p. 30). The similarity in composition is illustrated by the following formulas:

Number 

in table 7

A. Siderophyllites and aluminian lepidomelanes 

-0.06 -1.03 3^

2.44 

+0.35 -1.35

2.82 

+0.24 -1.19

B. Ferrous lithium micas (Li2 0<^.o percent) 

+0.06 -1.24

-1.07

2J58

+0.01

10-------............[(Alo. 71Feoti3Fe1+i4Mgo. 03 Mn0tJoLio.45)(Si2 . 93 Al 1 . 07)010 (OH,F) 2]- 1 - Q6K(Na) Ca/2)^e 08

2.76

+0.19 -1.11

^iiFe1tl4Mgo. 0!!MD0to22Lio. 47)(Si2 . 89Al1 . 11 )01 o(OH) F) 2]- 0 - 92K(Na,Ca/2)o+g890

2^86

In both these groups Mg is insignificant and Fe+2 is the 

dominant octahedral cation, but the amount of Fe+2 

present varies greatly. In some siderophyllites and in 

some of the ferrous lithium micas, Al is the principal 

trivalent octahedral cation, in others in both groups 

there are significant amounts of trivalent iron. Indeed 

some low-Mg, high-Fe+2 trioctahedral micas, lepidomelanes, contain trivalent iron as the greatly dominant 

octahedral cation. In formulas calculated from analyses of ferrous lithium micas, the dominant trivalent 

octahedral cation is usually Al, some contain considerable Fe+3, but Fe+3 is not greatly dominant in any of 

the calculated formulas studied. In the study of the 

phlogopite-biotite-siderophyllite (or lepidomelane) system (Foster, 1960), it was found that replacements of 

Mg by bivalent iron (Fe+2), and by the trivalent ions, 

Al and Fe+3, proceed quite independently; a given 

degree of replacement by Fe+2 has no relation to the
130 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

degree of replacement by Al or Fe+3, nor has the degree 

of replacement by Al any relation to the degree of 

replacement by Fe+8.

The octahedral charge in the siderophyllites and the 

ferrous lithium micas is usually positive, but it may be 

about neutral or even slightly negative, depending on 

how the additional positive charges carried by trivalent 

octahedral cations (as compared with the number of 

charges carried by bivalent cations) have been accommodated in the structure (Foster, 1960, p. 16), and the 

negative tetrahedral charge may be considerably greater 

than 1.00, close to 1.00, or less than 1.00, depending on 

the octahedral charge. Octahedral occupancy also 

varies considerably, depending also on how the additional positive charges of trivalent octahedral cations 

have been accommodated.

The similarity in characteristics of siderophyllites 

and ferrous lithium micas suggests that the siderophyllites are the prototypes from which the ferrous 

lithium micas are derived. It should be noted here 

that most analyses of siderophyllites and lepidomelanes 

include small amounts of Li2O. Some materials that 

have been called siderophyllite contain as much as 1 

percent of Li2O.

COMPOSITIONAL RELATIONS IN SIDEROPHYLLITES 

AND FERROUS LITHIUM MICAS

RELATION BETWEEN LI AND TKIVAIJENT OCTAHEDRAL) 

CATIONS

The relation between the number of formula sites 

occupied by Li and by trivalent octahedral cations (Al 

and Fe+3) in siderophyllites and ferrous lithium micas 

is shown in figure 34. The number of octahedral sites 

occupied by trivalent cations is more variable, and in 

general lower, in the siderophyllites and aluminian 

lepidomelanes and in the ferrous lithium micas having 

less than 1.5 percent of Li2O (about 0.5 octahedral 

sites), than in ferrous lithium micas containing more 

than 1.5 percent Li2O. In the latter the octahedral 

trivalent cationic content is remarkably constant over

>- 

m ^

Q P

OCTAHEDRAL' SITES OCCUR 

(PLU< TRIVALENT CATIONS 

P !-f^00 OQ) 5 co O

o 

)

o

0 °'

 

v:

.... EXF

S

Ferrc

* . 

 

=LANAT

o 

derophyllite

 

>us lithium i

M 

ON

s

TlicSS

00 0.20 0.40 0.60 0.80 1.00 1.20 1.4

OCTAHEDRAL SITES OCCUPIED BY U

FIGURE 34. Eelation between Li and octahedral B+8 cations in siderophyllites and 

ferrous lithium micas.

a range in Li2O content of from 1.5 to 4.8 percent. 

This relative constancy in octahedral trivalent cationic 

content suggests that these cations are not involved 

in the addition of Li to the structure.

RELATION BETWEEN LI AND FB«

The relation between Li and Fe+2 in siderophyllites 

and ferrous lithium micas is shown in figure 35, in

1.80 

1.60 

" 1.40

CO

o

UJ

I 1-2°

UJ

55 1.00 

1UJ.

I 

g 0.80

0.60 

0.40

0.20 

0.(

o

o

o 

o

.

^

^

N

X>

1

EXf

Ferro

N

 LAN ATI

o 

derophyllite

js lithium n

*

X

ON

licas

N

30 0.20 0.40 0.60 0.80 1.00 1.20 1.4

OCTAHEDRAL SITES OCCUPIED BY Li

FIGURE 35. Eelation between Li and Fe+J in siderophyllites and ferrous lithium

micas.

which the number of octahedral sites occupied by 

Fe+2 is plotted against the number of sites occupied by 

Li. The Fe+2 content of siderophyllites (including 

ferrian siderophyllites and aluminian lepidomelanes) 

varies greatly, as does also that of the ferrous lithium 

micas. Even those containing about the same amount 

of Li vary greatly in Fe+2 content. In general, however, there is a sharp downward trend of the points 

with increase in Li content, which is suggestive of replacement. The ratio of replacement is, however, 

difficult to determine because of the great variation in 

Fe+2 content in ferrous lithium micas having low Li 

content, as well as in the siderophyllites from which they 

are hypothetically assumed to have been derived, as 

indicated by the great variation in Fe+2 content in the 

siderophyllites at hand. Thus there is no definite point 

of departure with respect to Fe+2 content from which to 

calculate Fe+2 replacement as there was with respect to 

Al content and Al replacement in the lepidolites.
INTEBPRBTATION OF LITHIUM MICAS 131

RELATION BETWEEN U AND 81

The relation between Li and Si in siderophyllites 

(including aluminian lepidomelanes) and ferrous lithium 

micas is shown in figure 36, in which the number of

3.60

3.40

3.20

_j 3.00

2.80

2.60

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

OCTAHEDRAL SITES OCCUPIED BY Li

FIGXJKE 36. Eelation between Li and Si in siderophyllites and ferrous lithium

micas.

+0.19

formula sites occupied by Si is plotted against the number of formula sites occupied by Li. As in Fe+2 content, 

the Si content varies greatly, even in micas having about 

the same Li content. This difference in Si content in 

samples having about the same Li content is due to the 

manner in which the additional charges carried by 

trivalent octahedral cations are accommodated in the 

structure (Foster, 1960, p. 16). If the additional 

positive charges are accommodated predominantly as 

a positive charge on the octahedral layer and neutralized 

by a negative tetrahedral charge which is greater than 

1.00 by an amount about equivalent to the positive octahedral charge, the Si is considerably lower than if the 

additional positive charges are predominantly neutralized by anions associated with unoccupied octahedral 

sites. This variation in Si content, owing to differences 

in the way in which the additional positive charges 

were accommodated, in ferrous lithium micas with about 

the same Li content is illustrated in the formulas for 

analyses 22 and 23, table 7, that follow:

-1.20

2.99 

-0.18 -0.80

2.76

The La30 content in the micas represented by these 

formulas is almost the same, 3.39 and 3.40, respectively. 

But the SiO2 content of analysis 22 is only 39.04 percent, 

as compared with 46.37 percent in 23. In 22, octahedral 

occupancy is complete. Univalent Li compensates for 

0.98 of the additional 1.19 positive charges carried by 

Al, Fe+a, and Ti+4 ; the remainder form a positive charge 

(+0.19) on the octahedral layer that is neutralized by 

an equivalent increase, above 1.00, in the negative 

tetrahedral charge. In 23, only 2.76 octahedral sites 

are occupied. Univalent Li compensates for 0.94 of 

the 1.24 additional positive charges carried by Al and 

Ti; the rest are neutralized by negative charges associated with unoccupied octahedral sites. However, the 

0.24 unoccupied sites make 0.48 such negative charges 

available, and as only 0.30 are need to neutralize the 

uncompensated additional positive charges, the octahedral layer is left with a negative charge of 0.18. 

In order that the unit layer charge be close to 1.00, 

the negative tetrahedral charge must be less than 1.00

+0.24

£64 

+0.24

eoti8 

!U4

by the same amount. Because, therefore, of the different ways in which the additional positive charges 

carried by trivalent cations are accommodated in the 

structure in such trioctahedral micas as the ferrous 

lithium micas, there is considerable variation in Si 

content, even in those in which the Ii20 content is the 

same. However, despite such differences in SiO2 content, the upward trend of the points in figure 36 suggests 

that increase in Li content is accompanied by increase 

in Si content, although the angle of trend of increase is 

less than the angle of trend of decrease in Fe+2 content.

HYPOTHETICAL FE+2-LI REPLACEMENT RATIOS

If Li replaces Fe+2 in the ratio of 2:1, the number of 

positive charges carried by octahedral cations is not 

changed, and, consequently, the octahedral and tetrahedral charges and Si are unchanged, but the octahedral occupancy is increased by one-half the number of 

Li cations added. This is illustrated in the following 

formulas, in which 1.00 Li is substituted for 0.50 Fe+2 

in the formula for analysis 4, table 7.

-1.19

-1.19
132 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

The octahedral-tetrahedral charge relation and the Si 

are the same in the second formula as in the first, but 

octahedral occupancy is increased by 0.5 and is greater

than 3.00.

If, on the other hand, Li replaces Fe+2 ion for ion in 

the formula for 4, above,

-0.76 -0.19

2.64

the octahedral occupancy remains the same, but the 

layer-charge relation is greatly altered, and there is an 

increase in Si equivalent to the increase in Li and the 

decrease in Fe+2. The increase in Si, equivalent to the 

increase in Li and to the decrease in Fe+2, is greater than 

indicated by the comparative angles of trend of the 

points in figures 35 and 36, which indicate that the 

general increase in Si is generally less than the decrease 

in Fe+2. The negative octahedral charge is considerably 

greater, and the negative tetrahedral charge is considerably less, than in any of the calculated formulas of 

ferrous lithium micas.

Neither of these types of replacement of Fe+2 by 

Li, therefore, correlates well with the characteristics 

of the ferrous lithium formulas nor with the degree of 

Si-increase, Fe+2-decrease relation suggested in figures 

35 and 36. Substitution of Li for Fe+2 in the 2:1 ratio 

results in no change in Si content; substitution of Li 

for Fe+2 in the 1:1 ratio results in a greater increase in 

Si than indicated by figure 36. This suggests that 

the replacement ratio lies between 2:1 and 1:1. In 

the formula below, a replacement ratio of 2:1.5 (1 Li 

for 0.75 Fe+2) in the formula for analysis 4, table 7, is 

assumed.

[(Al0 . 44Tio.e

-0.26

ii .15) (Si3.3iAlo.69)010 (OHJF) 2]- 0 - 95K(Na,Ca/2)oH:i7 H98

89

In this formula, the increase in Si (+0.5) is equivalent 

to one-half the increase in Li content (+1.0) and to 

two-thirds the decrease in Fe+2 content (0.75). This 

relation between Li and Si is about that suggested by 

th.6 trend Of the points in figure 36, and the relation 

between Si increase and Fe+2 decrease is comparable 

to the relative trend of points in figures 35 and 36. 

The octahedral-tetrahedral charge relation in this formula and the octahedral occupancy are also comparable 

with those found in the calculated formula for ferrous 

lithium micas (the data for writing these calculated 

formulas are included in table 7). The replacement 

ratio probably varies considerably, possibly as much 

as from 2:1 to 1:1 Li for Fe+2 in certain specimens of 

ferrous lithium micas, but a replacement ratio of about 

2:1.5 Li for Fe+2 best explains in general the amount 

of decrease in Fe+2, the amount of increase in Si, the 

octahedral occupancy, and the octahedral-tetrahedral 

charge relations found in calculated formulas of ferrous 

lithium micas.

The changes in composition that take place in replacement of Fe+2 by Li in this ratio can be expressed 

briefly as 4n'Li+2nSi=3n'Fe+2+2n tetrahedral Al. 

Octahedral trivalent cations, Al and Fe+3, are not involved in the replacement, as is indicated in figure 34.

SIDEROPHYLLITE-LEPIDOLITE ISOMORPHOUS 

SERIES

The relation between Li, K+2 (Fe+2,Mn+2,Mg), and 

octahedral R+3 (Al,Fe+3)+Ti+4 in siderophyllites and 

aluminian lepidomelanes and ferrous lithium micas is

shown in figure 37, in which the percentages of occupied 

octahedral sites occupied by Li, R+2 (Fe+2,Mn+2,Mg), 

and octahedral R+3 (Al,Fe+3)+Ti+* in each of the calculated formulas used in this study are plotted on a 

triangular diagram. The points representing siderophyllites and aluminian lepidomelanes occupy an area 

at the base of the triangle just to the right of the center. 

Only one point, representing a siderophyllite in which 

no Li2O was reported, falls on the baseline. The other 

five points, which represent siderophyllites and lepidomelanes which contain small amounts of Li2O, fall a 

little above the baseline. The points representing the 

the ferrous lithium micas fall in a band trending diagonally upward from the area occupied by siderophyllites and aluminian lepidomelanes toward the point 

representing polylithionite. Calculated formulas representing progressive stages of replacement of ferrous 

iron by Al in the siderophyllite-lepidolite isomorphous 

series are given in table 4 and are represented graphically in histograms in figure 38. Both the formulas and 

histograms illustrate the progressive changes in composition that take place with increase in Li content, 

particularly decrease in Fe+2 content and increase in 

Si content.

The slight hiatus between points (fig. 37)representing 

siderophyllites and aluminian lepidomelanes and those 

representing ferrous lithium micas serves to differentiate the former and protolithionite, but differentiation 

between protolithionites and zinnwaldites must be on 

an arbitrary basis, as there is no hiatus between points 

representing these varieties.
INTERPRETATION OF LITHIUM MICAS

Li

133

EXPLANATION

* 

Ideal end member (polylithionite)

o

Siderophyllites and 

aluminian lepidomelanes

e 

Ferrous lithium micas

Polylithionite

Ferroan lepidolite 

to (cryophyllite)

Siderophyllites and aluminian

R+ 3 (Al, Fe +3)+Ti+4 R+ 2 (Fe+2 , Mn+ 2 , Mg) 

FIGURE 37. Relation between Li, R«(Fe-t-3 ,Mn+3>Mg), and octahedral R-t-3 (Al,FeM)+Ti+* in Siderophyllites and ferrous lithium micas.

Number in 

table 7

TABLE 4. Selected formulas representing steps in the siderophyllite-lepidolite series

Formula

3_.- ...-.._[(Alo.52Tio.c

+0.25

^22Mgo.O

-1.32

.13)(Si^gAh.32)OIQ(OH,F) 2]~ 1 - 07 K(Na,Ca/2)0 1.08

2.61

+0.06 -1.24

[(Ali.o6Ti0 .o3Fe 1H:?2 Mg0 .oiMnoH:g4Lio.42)(Si2 . 76Al1 .24)01 o(OH,F) 2]- 1 - 18 K(Na,Ca/2) 1t5415

2.68

-0.16 -0.93

15.._____..........._..._.[(Al1 .o4Feoto5Fe0H:l7Mgo.o6Lio.7i)(Si3.o7Alo.93)Oio(OH) F) 2]- 1 - 09 K(Na) 1+S8'

2.73 

-0.16 -0.79

18.__.._.-....__...___.._.[(Al1 . 08Fe0+g4Feo+l8Mn0t?0Li0 .92)(Si3 . 21A] 0 .79)01o(OH,F) 2]- 0 - 95 K(Na) 0+

-0.95 TrY-XT.^+0.94

2.82 

-0.40 -0.65

^^^

2.82 

-0.57 -0.42

(percent) 

0.39

1.44

2.42

3.28

4.18

4.99

2.85
134 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGT

Siderophyllite Protolithionites Zinnwaldites

Lepidolite 

(ferroan) 

Cryophyllite

4.00

0-°° - 9 15 18 31 35

SAMPLE 

FIGTTBE 38. Histograms of selected formulas representing steps in the siderophyllites-lepidolite series. (Numbers below histograms refer to analyses in table 7.)

SEDBROPHYLLITES AND LEPIDOMELANES

Siderophyllites and lepidomelanes are the high-Fe+2, 

low-Mg members of the trioctahedral Mg replacement 

system of which phlogopite, Mg3.o(Si3 .oAl 1 . 0)Oio(OH, 

F)2Ki>0, is the high-Mg, low-Fe+2 member (Foster, 

1960, p. 24). Heretofore it has been assumed that the 

high-Fe+2 end member of a Mg-Fe+2 replacement series 

is annite, Fe^(Si3 .oAl 1.o)O1o(OH, F)2K,. 0, the Fe+2 

analog of phlogopite, but a study of analyses of natural 

trioctahedral micas showed that no natural representative of such a mica has been recorded in the literature, 

that replacement of Mg by Fe+2 is also always accompanied by more or less replacement by Al and Fe+s, 

and, consequently, that the low-Mg, high-Fe+2 end of 

the system is represented not by annite but by siderophyllite, in which the principal octahedral trivalent 

cation is dominantly Al, and lepidomelane, in which 

it is Fe+3. High-Fe+2, low-Mg trioctahedral micas 

that contain both octahedral Al and Fe+s are termed 

ferrian siderophyllites, or aluminian lepidomelanes, 

depending on whether octahedral Al or Fe+3 is dominant.

In some formulas the amounts of octahedral Al and of 

Fe+3 present are about equal.

In most of the formulas calculated from analyses of 

ferrous lithium micas, Al is the predominent trivalent 

octahedral cation, although in a few formulas Fe+3 

is equal to, or slightly greater than, the octahedral Al. 

However, in none is Fe3 greatly dominant over trioctahedral Al. This suggests that the siderophyllites, 

ferrian siderophvllites, and aluminian lepidomelanes 

are prototypes of these minerals, but not lepidomelanes, 

in which Fe+3 is greatly predominant.

The available calculated formulas of these prototypes 

vary considerably in content of Fe+2, Fe+3, and octahedral Al. In the analyses at hand, Fe+2 ranges from 

1.22 to 1.88 occupied sites and averages 1.50, Fe+8 

ranges from 0.05 to 0.62 and averages 0.36, and octahedral Al ranges from 0.44 to 0.99 and averages 0.57. 

Total trivalent octahedral cations (R+3) range from 

0.81 to 1.14 occupied octahedral sites and average 0.93. 

The reciprocal extremes in R+8 and Fe+2 content are 

illustrated in the following formulas for analyses 2 and 

3, table 7,

+0.35 -1.35

[(Alo. 73FeoH:g8Fe1!|8Mgo.o1 Mno+g2Lio. 1o)(Si2 . 65Al1 . 35)01Q (OH.F)2]- 1 - 00K(NaiCa/2)oH:^99.

2.82 

+0.25 -1.32

[(Alo. S2Tio.o1Feo+c32Fe 1t|2Mgo.o9MDo+ §2Lio. 1 3)(Si2 . 68Al1 .32)Oio(OH> F) a]- 1 - 07K(NatCa/2)otii,06.

2JS1 

The first formula, calculated from analysis 2, table 7, 

has the highest Fe+2 content and the lowest octahedralR+3 content of the available analysis of siderophyllites 

and aluminian lepidomelanes; the second formula, calculated from analysis 3, table 7, has the lowest Fe+2

and the highest octahedral R+3. Thus siderophyllite, 

the prototype of the ferrous lithium micas, varies 

greatly in Fe+2, Fe+3, and Al content, just as ferrous 

lithium micas that contain about equal amounts of Li 

may vary widely in these constituents.
INTERPRETATION OF LITHIUM MICAS 135

In all but one of the analyses of siderophyllite the 

presence of a small amount of Li is reported.

PROTOUTmONITES

Kunitz (1924, p. 409) considered protolithionite the 

lithium-free member of a ferrous lithium mica series of 

which lepidolite was the high-Li end member, with a 

formula, KH2AlFe^2Si3Oi2, that is identical with Winchell's formula for annite. At this time Winchell (1927, 

p. 274) also considered protolithionite Li free, but 

heptaphyllic (or dioctahedral), with the formula 

H4K2Fe^2Al4Si5O22 . Later Winchell (1942, p. 117) 

recognized it as octaphyllic (or trioctahedral) and used 

is as an end member, representing the maximum tenor 

of bivalent cations together with a minimum tenor of 

Li, in interpreting the composition of lepidolites. In 

the formula which he then assigned to protolithionite, 

K2LiFe4~2Al3Si6O2oF4, Li occupies 1 unit-cell formula 

site. Hey (1955, p. 208) observes that Li occupies between 1 and 2 sites in the unit-cell formula.

Perhaps because of these considerable differences in 

the Li content in published formulas for protolithionite, 

published analyses for materials called protolithionite 

also vary considerably in Li content. JS'o analyses 

purported to be those of protolithionite were discovered in which no Li2O was reported, but one published as that of a protolithionite contained only 0.32 

percent of Li2O (O0.10 octahedral site in the half-cell 

formula), and another contained only 0.39 percent of 

Li2O. On the other hand, another analysis reporting 

4.57 percent of Li2O (O1.30 octahedral sites in the 

half-cell formula) was also called that of a protolithionite. The literature indicates, therefore, a state of considerable confusion as to the Li2O content of protolithionite.

In the present study the Li content of protolithionite 

is defined as 0.5±0.25 octahedral sites in the half-cell 

formula, or 1.00 ±0.50 sites in the unit-cell formula. 

This Li content is based on the Li content in the 

formula used by Winchell in 1942 and on Key's statement as to the Li content of protolithionite. A range 

is given for Li because these micas are interpreted as 

belonging to an isomorphous series, the members of 

which contain varying amounts of Li. This is the range 

bracketed opposite protolithionite in figure 37. The permissible site occupancy given is equivalent to a range of 

from about 0.75 to about 2.50 percent in Li2O content. 

Ferrous lithium micas containing a little Li2O but less 

than 0.75 percent, like those represented by points near 

the baseline in figure 37, are considered lithian siderophyllites, or lepidomelanes, depending on the Al and 

Fe+3 content. Those containing more than 2.50 percent of Li2O are considered zinnwaldites or ferroan 

lepidolites.

In the protolithionite analyses 7-15, table 7, Li varies 

from 1.19 to 2.42 percent Li2O, equivalent to a variation in octahedral sites of from 0.37 to 0.71 in the halfcell formula. FeO, as in the siderophyllites, is quite 

variable, ranging from 10.20 to 21.97 percent (0.61 to 

1.44 octahedral sites in the half-cell formula). The 

octahedral content of trivalent cations, Al and Fe+3, 

with Al usually dominant, is considerably more constant, varying only between 0.91 and 1.21 octahedral 

sites. These ranges in content of the principal octahedral cations can be expressed as follows:

I. 10±0.20)Fe1.00 0)Lio. 50±0.2s

Winchell assumes full octahedral occupancy in the 

formula for protolithionite that he used in 1942 in his 

interpretation of the composition of lepidolites. In 

this formula, recast in the half-cell notation used herein,

0.00 -1.00

3.00

the excess in positive charges carried by Al (as compared with the number of positive charges carried by 

bivalent cations) is exactly compensated by the deficiency in positive charges carried by Li, and the octahedral layer is neutral. All the charge on the unit 

composite layer is on the tetrahedral layers owing to 

the substitution of Al for one Si cation. However, in 

all the formulas calculated from analyses of natural 

protolithionites, the octahedral trivalent cations, Al 

and Fe4"3, with usually a little Ti, are considerably in 

excess of Li, so chat there are extra positive octahedral 

charges to be accommodated in the structure. In most 

of the calculated formulas the greater part of the additional positive charges are neutralized by negative 

charges associated with unoccupied octahedral sites, 

and there is only a slight positive charge on the octahedral layer to be neutralized by an equivalent negative 

charge in excess of 1.00 on the tetrahedral layers. In 

these formulas, octahedral occupancy ranges between 

2.63 and 2.88, and Si is less than 3.00, and ranges 

between 2.72 and 2.95. However, in three of the 

calculated formulas for protolithionites the octahedral 

layer has a negative charge, and Si is greater than 3.00. 

Exclusive of one formula in which Si is exceptionally 

high (3.43 tetrahedral sites), the range in the number 

of tetrahedral sites occupied by Si in the calculated 

formulas for protolithionite is from 2.72 to 3.17, appro ximatelv2.95±0.25.

The number of octahedral sites occupied by Fe+2 in 

the formulas calculated from analyses of protolithionite, 

as here defined, is generally higher than that specified 

by Hey (1955, p. 208). Key's value for Fe+2 , 0.75 

sites in terms of the half-cell formula, corresponds with
136 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

only the lower part of the range for Fe+2 found in the 

calculated formulas, 0.60 to 1.40. On the other hand, 

Hey's value for Si, 2.75 to 3.00 in terms of a half-cell 

formula, agrees fairly well with the Si content of the 

calculated formulas, 2.70 to 3.20. He}^ indicates that 

protolithionites contain little Fe+0, but more than half 

of the analyses had more than 2.5 percent of Fe2Oa and 

one had as much as 7.81 percent of Fe2O3 .

ZINNWAUJITES

Zinnwaldite was considered an intermediate member 

of the lepidolite-protolithionite system by Kunitz 

(1924, p. 409), Winchell (1927, p. 274), and Hallimond 

(1925, p. 311), and was not assigned a definite formula. 

Hey (1955, p. 208) gives the formula 2 [K2 (Li,Fe,+2Al)6 

(Si,Al)8O2o(F,OH)4] for zinnwaldite, with the observation that there is often considerable deficiency in the 

(Li,Fe+2,Al) group, and that typically Li«2, Fe+2 «lK, 

and Si«6K- On the basis of the Li content in this 

formula, the Li content of zinnwaldite is herein defined 

as 1.0 ±0.25 octahedral sites in the half-cell formula, 

or 2.00±0.50 octahedral sites in the unit-cell formula. 

Again a range is given because these micas, as members 

of an isomorphous series, contain varying amounts of 

Li, as well as of the other constituents. This is the 

range bracketed opposite zinnwaldite in figure 37. The 

defined range in octahedral-site occupancy is equivalent 

to a Li2O content of from about 2.50 to about 4.50 

percent.

In the zinnwaldite analyses 16-31, table 7, Li2O 

varies from 2.62 to 4.18 percent, equivalent to octahedral-site occupancies of 0.80 to 1.16 in the half-cell 

formulas. FeO is generally lower than in the protolithionites and not quite so variable, ranging from 6.35 

to 12.22 percent (0.37 to 0.79 octahedral sites in the 

half-cell formulas). In general, the contents of Li2O 

and FeO in these analyses bear a reciprocal relation to 

each other: the lower contents of Li2O are associated 

with the higher contents of FeO, and vice versa. The 

octahedral content of the trivalent cations Al and Fe+3 

in the half-cell formulas for zinnwaldites is quite constant, varying only between an occupancy of 1.07 and 

1.26 sites, with no apparent relation between octahedral R+3 and Li content. In most of the analyses of 

zinnwaldite the amount of Fe2O3 present is very small, 

and octahedral Al is the greatly dominant R+3 cation 

in the formulas calculated from these analyses, but 

several analyses contain significant amounts of Fe2O3 , 

and in the formulas calculated from these analyses 

Fe+3 may occupy about as many or even more octahedral sites than Al. The ranges in octahedral content 

of the principal cations in half-cell formulas for zinnwaldites are summarized in the following expression:

(-"'1.15±0.10»Fe0.65±0.20»Lil.OO±;2«)-

Octahedral occupancy in the zinnwaldites is generally 

between 2.75 and 3.00. Only 1 calculated formula for 

a zinnwaldite (21, table 7) had an octahedral occupancy 

significantly lower than 2.75. This formula has an 

octahedral occupancy of only 2.62. In most of the 

calculated formulas the octahedral charge is negative. 

Consequently, Si in these formulas is generally in excess 

of 3.00 and ranges from 3.03 to 3.46. However, in 3 

calculated formulas (17, 22, and 25, table 7) the octahedral group had a positive charge, and Si was less than 

3.00 2.82, 2.80, and 2.95. Thus the range in the 

number of tetrahedral sites occupied by Si in the 

calculated formulas for zinnwaldites is quite wide, 

2.80-3.46, or 3.15 ±0.35.

The amounts of Fe+2 and Si in the calculated formulas 

herein defined as those of zinnwaldite differ somewhat 

from the amounts indicated by Hey (1955, p. 208) as 

present in zinnwaldite. Hey's value for Fe+2, about 

IK sites in the unit-cell formula, represents the high 

end of the range of Fe+2 present in the calculated formulas. The median value for Fe+2 present, in terms of 

the unit-cell formula, is much closer to 1.00 (1.10) 

than to 1.5 octahedral sites. Hey's value for Si, 

about 6% sites in the unit-cell formula, is somewhat 

higher than the median and average value for Si found 

in the calculated formulas, which is 6.3. Hey's formula 

for zinnwaldite includes no Fe+3, although his formulas 

for protolithionite and cryophyllite both include Fe+3. 

As pointed out above, some of the calculated formulas 

containing the amounts of Li to be found in zinnwaldite, as defined by Hey, contain appreciable 

amounts of Fe+3.

FEKROAN LEPrDOIJTE (CRYOPHYULTTE)

The name cryophyllite was given by Cooke (1867, 

p. 217) to a micaceous mineral found in the granite 

ledges that form the extremity of Cape Ann, Mass. 

Cooke's analyses of two types of this material showed 

them to have virtually the same chemical composition. 

Later, in 1886, three different types of cryophyllite 

from Cape Ann were analyzed by R. B. Riggs (Clarke, 

1886, p. 358). These three types were also virtually 

identical in chemical composition and were similar to 

those analyzed by Cooke, except that Riggs obtained 

somewhat higher values for Li2O 4.81, 4.87, and 4.99 

percent, compared with Cooke's 4.05 and 4.06 percent. 

No other occurrence of a ferrous lithium mica having 

a comparable Li2O content has been reported in the 

literature. On the basis of these analyses, particularly 

those of Riggs, cryophyllite has been considered a 

variety of zinnwaldite (Dana, 1892, p. 626, and Hey, 

1955, p. 208) with a somewhat higher Li and lower 

Fe+2 content. The relation between cryophyllite and 

zinnwaldites is shown in figure 37.
INTERPRETATION OF LITHIUM MICAS 

The formula calculated from the average of Riggs' 3 analyses (33, 34, and 35, table 7),

137

-0.60 -0.42

has a Li content similar to that of Stevens' sample 7 (34, table 6), a 6-layer lepidolite,

-0. 41 -0. 62

[(All . 29Feo+ §1 Mn0+f6Lil .38)(Si3.38Alo.62)01 o(F> OH) 2]- 1 - 03K(Na,Rb >Cs)^303 ,

and does not greatly exceed Stevens' sample 10 (42, table 6), a 1-layer lepidolite,

-0.50 -0. 52

[(Al1 . 10Tio.o1 Feo+g2Feo+ fsMn0+fsLil . 59 )(Si3.48Alo. 52 )010 (F>OH) 2]- 1 - 02K(Na,Rb,CS) 0+g999, 

£93

in content of R+i cations. In the formula for cryophyllite, R+2 is made up almost entirely of Fe+2 ; in 

the formula for Stevens' sample 10, R+? is made up 

equally of Fe+° and Mn+? . These two formulas also 

have about the same ocatahedral-R+3 content, although 

in the cryophyllite formula Fe+3 occupies 0.16 octahedral 

sites and in Stevens' sample 10 only 0.03 octahedral 

sites. Thus Li2O content and the relation between 

Li, Fe+2 (Mg, Mn+2 ), and R+3 (A1, Fe+3 ) in the material 

called cryophyllite are comparable with that in some 

lepidolites. It is, therefore, recommended that the 

material known as cryophyllite be considered a ferroan 

variety of lepidolite, and that the name cryophyllite be 

discarded.

RELATION BETWEEN ALUMINUM LITHIUM MICAS AND 

FERROUS LITHIUM MICAS

The relation between the aluminum lithium micas 

and the ferrous lithium micas is illustrated in figure 39 

(which combines fig. 33), which shows the Li, R+2 (Fe+2, 

Mn+2 , Mg), and octahedral R+3 (A1, Fe+3 )-f-Ti+4 relation in aluminum lithium micas, and figure 37, which 

shows the same relation in ferrous lithium micas. 

Lepidolites are aluminum lithium micas and, as such,

were discussed with other aluminum lithium micas, 

and their composition was interpreted as if derived 

from muscovite by replacement of octahedral Al by Li. 

However, figure 39 shows that complete, or almost 

complete, replacement of Fe+2 in siderophyllite also 

produces lepidolites. Thus the lepidolite composition 

can be interpreted as the result of two different series 

of replacements.

The following equations show the general course of 

evolution of lepidolite from muscovite and from siderophyllite, using the average Li-(octahedral Al) and 

Li-Fe+2 replacement ratios found in the natural micas:

Muscovite to lepidolite

00 0.00 -1.00

Muscovite-4Al2 .oo(Si3 .ooAl1 .oo)O10 (OH)2]- 1 - 00 Kil:Jb

Lithian -o.io -0.90

muscovite.-[(Al 1 . 8oLio. 5o)(Si3. 1 oAlo. 90)01 o(OH: > F)2]- 1 - 00 KltSo00

' 2~S

Mixed structures

-0.30 -0.70

Lepidolite__[(Al1 .4oLi1 . 5o)(Si3 .3oAlo.7o)010 (F,OH)2]- 1 - 00K1tS600

2.90

Siderophyllite to lepidolite

+0.15 -1.15

Siderophyllite

-0.19 -0.81

Protolithionite.._.._._..-.-.._[(R1t§5Feff2Lio.5o)(Si3.i 9Alo.8i)Oio(OH,F) 2]- 1 - 00 K1

- 1 -0000

2.67

-0 35

Zinnwaldite

Lepidolite

2.80

-0.61

-0.65

-0.39

.[(R1+ ^Fe0+ |7Li1 .5i)(Si3 .6iAl;. 39)0IO (F,OH) 2]- 1 - 00 K 1+ j6'

2.92
138 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Polylithionite

Lepidolites

EXPLANATION

Ideal end members

Lithian muscovites and 

transition micas

Lithian muscovites and transition 

micas whose structure has 

been studied

o

Siderophyllites, aluminian iepidomelanes, 

and ferrous lithium micas

A

Lepidolites

Lepidolites whose structure has 

been studied

Indefinite boundary

o\ Siderophyllites and

Mixed forms

Lithian muscovites

Muscovite

Octahedral R+ 3 (A!, Fe +3) + Ti+ 4 R+ 2 (Fe+2 ,Mn+ 2 , Mg) 

FIGURE 39. Relation between Li, R« (Fe«, Mn«, Mg), and octahedral R«(A1, Fe+3)+Ti«, in lithium micas.

Replacement of octahedral Al in muscovite by Li in 

the ratio of 2 Li for 1 octahedral Al leads to polylithionite,

-1.00 0.00

IYA1 T; 1<a; n T? l-l.oo K-+I.CO U Ali.ooLila. OOJOI4. OO^lO-f 2J J^l.00 »

JT65'

as the high-Li end of the series, but in the natural 

aluminum lithium micas studied the replacement ratio 

varied between 2 and 3 Li for 1 octahedral Al. In the 

series above, therefore, the replacement ratio used is 

2.5 Li for 1.0 octahedral AL At this replacement 

ratio the greatest number of octahedral sites that Li 

can occupy is 1.68, with Al occupying 1.33 sites. 

Among the formulas for lepidolite, only 2 (57 and 58, 

table 6) had a higher Li occupancy, 1.84 and 1.93 sites, 

respectively. In these 2 formulas the Li-(octahedral 

Al) replacement ratio is 2.0, and they are close to polylithionite. Aside from these 2 formulas, the lepidolite 

formula having the highest Li occupancy is 56, table 6, 

in which Li occupies 1.68 sites and AI(+Mn+2) occupies 

1.30 sites, and the Li- (octahedral Al) replacement ratio 

is 2.4. This formula, therefore, is almost identical with 

that of the high-Li end of the series shown above, in 

which the Li- (octahedral Al) replacement ratio is 2.5.

The series of form alas shown for the evolution of 

lepidolite from siderophyllite is based on the averages 

of the formulas at hand for siderophyllite, protolithionite, and zinnwaldite. The generalized formulas for 

these averages show an average replacement ratio of 

2.0 Li for 1.5 Fe+2. Extension of this series of formulas 

at the same replacement ratio to the highest Li occupancy produces a formula,

-0.78 -0.22
INTERPRETATION OF LITHIUM MICAS 139

which is close to polylithionite and very like the formula 

for 57, table 6,

-0.17

296

These two series of formulas, one starting with muscovite, the other with siderophyllite, produce formulas for 

lepidolite that have the same Li occupancy but which 

differ considerably in octahedral-R+3 occupancy. They 

also differ in Fe+2 content, but this is not so significant 

as the difference in octahedral-R+3 content, becaase the 

ferrous lithium micas themselves differ considerably in 

Fe+2 content and could produce a lepidolite containing 

little or no Fe+3. On the other hand, the octahedralR+3 content in the lepidolite formulas and the range of 

octahedral-R+3 occupancy found in ferrous lithium 

micas may serve to suggest the source of certain lepidolites.

In some of the calculated formulas of lepidolites in 

which Li occupies fewer than 1.60 sites, octahedral Al 

is higher than that found in any of the calculated formulas for siderophyllite, protolithionite, or zhuwaldite. 

Such lepidolites may be interpreted as derivations of 

muscovite. In other lepidolite formulas having fewer

than 1.60 sites occupied by Li, octahedral Al occupancy 

is comparable with that in calculated formulas for 

siderophyllites and ferrous lithium micas in which 

octahedral R+3 is made up almost entirely of Al. Such 

lepidolites can be interpreted as possibly derived from 

siderophyllite. The very low Fe+3 content of these 

lepidolites indicates, however, a highly aluminian 

siderophyllite as the possible source. None could have 

been derived from siderophyllite containing significant 

amounts of Fe+3, or from aluminian lepidomelane, as 

can some of the protolithionites and zinnwaldites.

In the two lepidolite formulas in which Li occupancy is 

greater than 1.70 sites (57 and 58, table 6), the lepidolites they represent can be interpreted as having been 

derived either from muscovite, at a Li-(octahedral Al) 

replacement ratio of 2:1, or from siderophyllite.

UNUSUAL LITHIUM MICAS

Four analyses of lithium micas can not be interpreted 

as if derived by replacement from either muscovite or 

siderophyllite. One of these is the analysis of the rare 

mica, taeniolite, made by Stevens (Miser and Stevens, 

1938, p. 106) from Magnet Cove, Ark. (1, table 5). 

The formula calculated from this analysis,

 0.98 -0.03

2.89

resembles that of a phlogopite in which about 0.84 Mg had been replaced by 0.84 Li,

-0.10 -0.87

The deficiency in the amount of positive charge carried 

by the Li cations results in a negative charge on the 

octahedral layer, which necessitates an equivalent decrease in the negative charge on the tetrahedral layers. 

The sample is very low in both octahedral and tetrahedral Al, and Si, which occupies almost all the tetrahedral sites, is quite high. This specimen is very close 

to the ideal high-Li end member of a hypothetical 

phlogopite-taeniolite series,

o.oo -i.oo 

[Mg3.oo(Si3.ooAl1 .oo)010 (OH) 2]- 1 - 00 K1+ j600

-0.50 -0.50

[(Mg2 . 5 Lio. 5o)(Si3. SoAlo. 5o)01 o(OH) 2]- 1 - OQ K1+ 0600 *

-1.00

[(Mg2 .ooLi1 .oo)Si401o(OH) 2]- 1 - 00 Kx+Jo00 

* iToo

This specimen has a 1-layer structure (monoclinic hemihedral), as determined by Hendricks and Jefferson 

(1939, p. 758).

TABLE 5. Analyses oflithian micas that do not fit in the aluminum 

lithium or ferrous lithium series

SiOj.... .. 

TiOj 

AhOs 

FezOa

FeO. 

MnO- _ - - ___ __ _ .-

MgO 

CaO. 

L12 0 

NasO. ................................

~K.^O. ....................................

I<.\MO. ...................................

CsjO. 

HjO--- - ----- - _ 

HjO+ 

F. .... __ ... __ . . . ____ ....

Total. ___ . ___ .. .............

(0=F) 

Total....... ___ . ________ .

1

58.82 

.11 

1.29 

.40 

.24

19.18

3.10 

.64 

10. 44

.09 

.59 

8.56

103. 46 

-3.60

99.86

2

42.02 

1.35 

18.75 

.66 

8.29 

.27 

9.55 

.93

1.20 

.73 

8.54 

1.85 

.47

.18 

2.44 

4.34

101. 55 

-1.83

99.72

3

35.61 

1.46 

20.03 

.13 

21. 85 

1.19 

5.23

.93 

.52 

9.69

} 1.87 

.76

99.27 -.32

98.95

4

36.97 

2.64 

17.51 

2.26 

14.81 

.22 

8.45 

None 

.65 

.46 

8.48 

1.48 

1.12 

( .32 

I 2.48 

3.17

101.01 

-1.33

99.68

1. Magnet Cove, Ark. (Miser and Stevens, 1938, p. 106). Associated with clay and 

novaculite. 

2. Kinps Mountain, N.C. (Hess and Stevens, 1937, p. 1044, analysis 1). From mica 

schist it contact with spodumene pegmatite. 

3. Mtddletown, Conn. ("Dana, 1892, p. 030, analysis 29). 

4. Tin Mountain, S. Dak. (Hess and Stevens, 1937, p. 1044, analysis 2).
140 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

The formulas calculated from analyses 2, 3, and 4, table 5,

-0.20 0.95

2.66

+0.28 ~t~U. £o -1.29 * ***>

[(Alo. 51Tio.o8Feo+ g 1Fe1+ l9Mgo. 59Mn0^8Li0 . 28)(Si2 . 71 Al1 . 29)01 o(OH,F)2 ]- 1 - 01K(Na) 1+^02, and

2.94 

+0.18 +0.18 1.18

[(Alo. 39Tio. 15Feo+ f3Feo+ i4Mgo. 96Mno+§ 1Lio. 2o)(Si2 . 82Al1 . 18)Q1 o(QH,F)2]- 1 - 00K(Na,Rb,Cs)i+ o600 ,

2.78

respectively, resemble biotites in which some Fe+2, or 

Mg, has been replaced by Li.

SUMMARY

The composition of most lithium micas can be interpreted as if derived from muscovite, by the replacement 

of octahedral Al by Li, or from siderophyllite, by the 

replacement of Fe+2 by Li. In the aluminum lithium 

micas Li replaces octahedral Al in ratios varying between 2 and 3 Li for 1 octahedral Al, with an average 

replacement ratio of about 2.5. Increasing Li content is, therefore, accompanied by increasing octahedral 

occupancy, from 2.00 in muscovite to about 3.00 in 

some lepidolites. Correlation of calculated formulas 

with the structural work of Hendricks and Jefferson 

and of Levinson indicates that a change in structure to 

the lepidolite structure takes place when the octahedral 

occupancy is about half way between 2.00 and 3.00 and 

Li occupancy is about 1.00 (equivalent to about 3.75 

percent Li2O). Because of the disparity between the 

amount of positive charge carried by the replacing Li 

cations and the replaced Al cations, increase in Li content is also accompanied by increase in the amount of 

negative charge on the octahedral layer and by decrease 

in tetrahedral Al and increase in Si, with consequent 

decrease in the negative charge on the tetrahedral 

layers. Thus the chemical characteristics of the 

aluminum lithium micas with increase in Li are: decrease 

in both octahedral Al and tetrahedral Al, increase in Si? 

and increase in octahedral occupancy. However, the 

aluminum lithium micas are not members of a continuous series; the series is broken at about the halfway 

point by the structural change necessitated by increase 

in octahedral occupancy.

Starting with siderophyllite (ferrian siderophyllite, 

or aluminian lepidomelane), the ferrous lithium micas 

form a series in which Li progressively replaces Fe+2 in 

an approximate ratio of 2.0 Li for 1.5 Fe+2. Ferrous 

lithium micas in which Li occupies fewer than 0.25 

octahedral sites are termed lithian siderophyllites, 

lithian ferrian siderophyllites, or lithian aluminian

lepidomelanes, depending on the Fe+3 content; those in 

which Li occupies between 0.25 and 0.75 sites are 

defined as protolithionites; those in which Li occupies 

between 0.75 and 1.25 sites are defined as zinnwaldites; 

and those in which Li occupies more than 1.25 sites are 

considered lepidolites. Thus the high-lithium mica 

described by Cooke, and named cryophyllite, is considered a ferroan lepidolite. The greatest number of 

octahedral sites that can be occupied by Li, at the 

approximate Li-Fe+2 replacement ratio and at the 

average octahedral R+3 content found in these micas, 

is 1.85,

-0.78 -0.22

[(Ri+ c35Fe^f1Li1 . 8 ,)(Si3. 78Alo. 22)01 o(F,QH) 2]- 1 - 00 K1+^00 .

In siderophyllites and protolithionites, R+3 may consist 

entirely of Al or may contain significant amounts of 

Fe+3 , but in most zinnwaldites R+3 is made up predominantly of Al. Fe+3 is low in all the lepidolites. In 

this series, as in the aluminum lithium mica series, increasing Li content is accompanied by increasing octahedral occupancy, but the increase is not as great, and 

the ferrous lithium micas are trioctahedral throughout, 

except perhaps for some siderophyllites and protolitbioiiites in which octahedral occupancy is less than 

2.50. Increase in octahedral negative charge and 

decrease in tetrahedral negative charge also accompany 

increase in Li content. Thus the compositional characteristics of the series are increase in Li content, 

decrease in Fe+2 content, decrease in octahedral Al 

content, and increase in Si content.

The two series join in lepidolite. Lepidolites derived 

from siderophyllite would be expected to be lower in 

octahedral and tetrahedral Al, for the same Li content, 

than lepidolites derived from muscovite; they would 

also be higher in Fe+2, although not necessarily, as the 

ferrous lithium micas vary considerably in Fe+2 content. 

The ideal end member of both series is polylithionite,

-1.00 0.00 -1.00

3M
INTERPRETATION OP LITHIUM MICAS 141

REFERENCES CITED

Berggren, Thelma, 1940, Minerals of the Varutrask pegmatite, 

pt. 15 Analyses of mica minerals and their interpretation: 

Geol. Foren Stockholm Forh., v. 62, p. 182-193.

 1941, Minerals of the Varutrask pegmatite, pt. 25 

Some new analyses of lithium-bearing mica minerals: 

Geol. Foren. Stockholm Forh., v. 63, p. 262-278.

Buryanova, E. S., 1940, An account of the mineralogy of granite 

pegmatites from the Korosten plutone massif in Yolhynia 

and of a study of their iron biotites: Mineralog. obshch., 

Leningrad, Zapiski, ser. 2, v. 69, p. 519-540.

Clarke, F. W., 1886, Researches on lithia micas, pt. 2 The 

iron-lithia micas of Cape Ann: Am. Jour. Sci., 3d ser., 

v. 32, p. 358-361.

 1910, Analyses of rocks and minerals from the laboratory

of the U.S. Geological Survey, 1880-1908: U.S. Geol. Survey

Bull. 419, 323 p. 

Cooke, J. P., Jr., 1867, On cryophyllite, a new mineral species

of the mica family, with some associated minerals in the

granite of Rockport, Massachusetts: Am. Jour. Sci., 2d

ser., v. 43, p. 217-230. 

Dana, E. S., 1892, The system of mineralogy, 6th ed.: New

York, John Wiley and Sons, 1104 p. 

Duparc, Louis, Wunder, M., and Sabot, R., 1910, Les mineraus

des pegmatites des environs d'Antshirab6 a Madagascar:

Mem. Soc. phys. et histoire nat. GeneVe, v. 36, p. 363-410. 

Foster, M. D., 1956, Correlation of dioctahedral potassium

micas on the basis of their charge relations: U.S. Geol.

Survey Bull. 1036-D, p. 57-67.

 1960, Interpretation of the composition of trioctahedral

micas: U.S. Geol. Survey Prof. Paper 354-B. 

Ginzburg, A. I., and Berkhin, S. I., 1953, On the composition

and chemical constitution of the lithium micas: Mineralog.

Muzeya. Akad. Nauk U.S.S.R. Trudy, v. 5, p. 90-131. 

Hallimond, A. F., 1925, On the chemical classification of the

mica group, 1. The acid micas: Mineralog. Mag., v. 20,

p. 305-318. 

Heinrich, E. W., and Leviiisoii, A. A., 1953, Studies in the mica

group; Mineralogy of the rose muscovites: Am. Mineralogist

v. 38, p. 25-49. 

Hendricks, S. B., and Jefferson, M. E., 1939, Polymorphism of

the micas: Am. Mineralogist, v. 24, p. 729-771. 

Hess, F. L., and Stevens, R. E., 1937, A rare-alkali biotite from

Kings Mountain, North Carolina: Am. Mineralogist, v.

22, p. 1040-1044. 

Hey, M. H., 1955, An index of mineral species and varieties. 2d

rev. ed.: London, British Museum (Nat. History), 728 p. 

Kunitz, Wilhelm, 1924, Die Beziehungen zwischen der chemischen

Zusammensetzung und der physikalisch-optischen Eigenschaften innerhalbder Glimmergruppe: Neues Jahrb. Mineralogie, Geologie, u. Palaontologie, Beilage-Band 50, p.

365-413. 

Levinson, A. A., 1953, Studies in the mica group; relationship

between polymorphism and composition in the muscovitelepidolite series: Am. Mineralogist, v. 38, p. 88-107. 

Litvin, O. L., 1956, The lithium-ferrous micas from pegmatites

of Volhynia: Kiev Derzhav. Univ. Nauk. Zapiski, v. 15,

no. 2, Zbirnik Geol. no. 6. p. 119-128.

Marshall, C. E., 1949, The colloid chemistry of the silicate

minerals: New York, Academic Press, 195 p. 

Meng, H. M., and Chang. K., 1935, Geology of the Hsianghualing tin deposits, Lingxvu, Hunan: Nat. Research Inst.

Geology (Acad. Sinica), Mem., no. 15, p. 15-72. 

Miser, H. D., and Stevens, R. E., 1938, Taeiiiolite from Magnet

Cove, Arkansas: Am. Mineralogist, v. 23, p. 104-110. 

Nockolds, S. R., and Richey, J. E., 1939, Replacement veins in

the Mourne Mountains granites, N. Ireland: Am. Jour.

Sci., v. 237, p. 27-47. 

Pehrman, Gunnar, 1945, Die Granitpegmatite von Kimito

(S.W.-Finnland) uud ihre Minerale: Acad. Aboensis math.

et phys. Acta 15, no. 2, 84 p. 

Saldariha, Reynaldo, 1946, O estudo da jazida de wolframita de

Inhandjara: Sao Paulo Univ., Fac. Filosofia Bol. 60 (Mineralogica, no. 8), p. 1-95. 

Schaller, W. T., 1930, Adjectival ending of chemical elements

used as modifiers to mineral names: Am. Mineralogist, v.

15, p. 566-574. 

Shibata, H., 1952a, Spodumene and ambligonite from the Bunsen

Mine and other localities in Korea: Tokyo Bunrika Daigaku,

Sci. Repts., sec. C., v. 2, no. 11, p. 145-154.

 1952b, Mineralizations in granite-pegmatites in Japan

and Korea: Tokyo Bunrika Daigaku, Sci. Repts., sec. C.,

v. 2, no. 12, p. 155-206. 

Shilin, L. L., 1953, On lithium micas from pegmatites of alkaline

magmas: Mineralog. Muzeya. Akad. Nauk LT.S.S.R. Trudy,

v. 5, p. 153-163. 

Simpson, E. S., 1927, Contributions to the mineralogy of Western

Australia: Royal Soc. Western Australia Jour., v. 13, p.

37-48. 

Smith, J. V., and Yoder, H. S., Jr., 1956, Experimental and

theoretical studies of the mica polymorphs: Mineralog.

Mag., v. 31, p. 209-235. 

Stelzner, A. W., 1896, Contribution on the lead ore of Freiberg

and the tin ore of the Erzgebirge: Zeitschr. prakt. Geologie.

v. 4, p. 377-412. 

Stevens, R. E., 1938, New analyses of lepidolites and their

interpretation: Am. Mineralogist, v. 23, p. 607-628. 

Stevens, R. E., and Schaller, W. T., 1942, The rare alkalies in

mic;is: Am. Mineralogist, v. 27, p. 525-537.

Tsyg.-nov, E. M., 1954, The lithium mic;-;? of Yolhynia: Mineralog. Obshch., Leningrad, Zapiski, ser. 2, v. 83, no. 4, p.

383-397. 

Ukai, Yasuo, Nishimura, Shinichi, and Hashimoto, Yoshikazu,

1956, Chemical studies of the lithium micas from the

pegmatite of Minagi, Okayama Prefecture: Mineralog.

Jour. Japan, v. 2, no. 1, p. 27-38. 

Walker, T. L., and Parsons, A. L., 1924, Pegmatite minerals

from New Ross, Nova Scotia: Toronto, Univ., Studies,

Geol. ser., no. 17, p. 46-50. 

Wells, R. C., 1937, Analyses of rocks and minerals from the

laboratory of the United States Geological Survey, 1914-

1936: U.S. Geol. Survey Bull. 878, 134 p. 

Wincbell, A. N., 1927, Further studies in the mica group: Am.

Mineralogist, v. 12, p. 267-279.

 1942, Further studies of the lepidolite system: Am. 

Mineralogist, v. 27, p. 114-130
142 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

TABLE 6. Analyses, with data for writing formulas, of aluminum lithium micas used in interpretation of composition

[In order of increasing Li2O content]

Analysis *

1.

2.. ...

3.................

4.................

5.. .............

6. .............

7.................

8. _ .............

9.. ............. ..

10................

11. _ ............

12................

13.. ..............

14 __ .. __ ......

15 _ .............

16 __ . . .

17 _ .............

18................

19...............

20................

21. . ..............

22................

23................

24................

25.. ....... .......

26. _ ............

27................

28................

29........ .. ....

30 .............

31.-.. ...... ..

32....... .........

33- . -

34--. 

35 _. . 

36.... .. .

37

38- 

39. 

40 .

41_._ .

42-.-. . ..

43 . 

44- 

45- . 

46

47. . 

48--.. ..

49- 

50- . 

51-. 

52

53- 

54---.. .

55-. .

56. 

57- . 

58.-. ......

Percent

SiO3

45.54 

44.85 

44.10 

45.22 

44.80 

42.30 

45.03 

43.65 

45.24 

45.60 

46.01 

45.18 

46.17 

42.90 

47.64 

46.24 

41.52 

43.24 

46.30 

46.34 

47.00 

49.50 

48.58 

50.20 

49.52 

48.68 

50.30 

49.14 

49.29 

49.62 

51.52 

48.94 

53. 45 

49.58 

49.19 

54.69 

57.44 

51.88 

51.70 

50.16 

49.28 

50.31 

49.14 

50.92 

51.10 

48. 9G 

52.58 

49.18 

50.60 

51.25 

51.67 

51.07 

49.80 

51.40 

58.56 

52.57 

57.03 

59.56

A12 O3

36.36 

37.20 

33.04 

37.46 

37.72 

33.50 

36.33 

32.54 

36.85 

35.96 

35.64 

35.76 

35. 57 

31.00 

34.22 

32.37 

32.58 

33.90 

33.08 

32.47 

30.60 

28.06 

28.93 

28.18 

28.80 

29.62 

25.49 

27.66 

28.40 

27.30 

25.96 

22.21 

22.15 

23.87 

24.81 

22.83 

15. 50 

20.65 

23.97 

23.54 

24.36 

19.95 

21.90 

25.12 

23.98 

20.12 

22.82 

18.85 

25.42 

23.71 

23.22 

22.05 

25.56 

17.95 

14.97 

23.01 

15.55 

12.04

TiO2

0.07 

.04 

.14

.05 

.02 

.14 

.01 

.03 

.00 

.15 

.00 

.46 

.00 

.10 

.28 

.24 

.00 

.06 

Tr. 

Tr. 

Tr. 

Tr.

.00 

Tr. 

.00 

Tr.

.00 

Tr. 

.06 

.08 

Tr.

.21 

Tr. 

.00

.22 

.08 

.00 

Tr. 

.13 

Tr. 

.12 

.00 

.01 

.06 

.06 

.00 

.02 

.36 

.04 

.03 

.48

Fe2 03

0.25 

.40 

2.95 

Tr. 

.67

.97 

.14 

2.62 

.09 

.10 

.13 

.00 

.15 

4.79 

.10 

1.34 

.88 

.55 

.00 

.00 

.26

.40 

.10 

.05

.31 

.31

1.55

.50

.79

.46 

.63

.49 

.44 

.06

.40

.42 

.28

.08

.43 

.08

.13

FeO

0.02 

.45 

.50 

.56

1.20 

.02 

1.63 

.02 

.02 

.00 

1.52 

.08 

.70

1.14 

.94 

1.38 

1.20 

1.06 

.41

8.11

 .04 

3.04 

.24 

.00 

1.30 

3.43 

3.05 

.07

1.52

3.16 

3.21

3.24 

s.ll

1.99 

3.04 

1.27

2.55 

.24 

.00 

Tr. 

.18 

.01 

.16 

.02 

8.07 

6.04 

3.23 

.00

3.21

3.12

.42

MgO

0.07 

Tr. 

.33 

.38

.16 

.05 

1.06 

.08 

.05 

.04 

.07 

.00 

.22 

.28 

.19 

.10 

.26 

.14 

.00 

.13 

.00 

.00 

.00 

.02 

.00 

.38 

.05 

.12

.02 

.03 

.14 

.00 

.05 

.00 

1.70 

.00 

.00 

.06 

.73 

.02 

.88 

.06 

.00 

.32 

.00 

1.24 

.00 

.08 

.30 

.09 

.22 

.30 

1.30

.22 

.34

MnO

0.80 

.02 

.03

.71

.01 

.41

.12 

.37

.09 

.11 

.04 

.00 

.05 

.09 

.00 

.01 

.28 

.35 

2.04 

.54 

.92 

.28 

.07 

.28 

.53 

1.22 

.65 

.55 

.20 

.75 

.52 

2.78 

2.51 

.14 

Tr. 

2.01 

.17 

.79 

.87 

2.63 

1.41 

.52 

.13 

1.32 

.28 

1.77 

.15 

.61 

1.37 

.76 

.38 

2.06 

.14 

.63 

.72 

.03

Li2 0

0.06 

.07 

.24 

.32 

.38

.40 

.41 

.46

.49 

.63 

.69 

.73 

.76 

.80 

1.10 

1.1 

1.51 

1.53 

1.80 

2.45 

2.70 

3.51 

3.70 

3.81 

3.87 

3.9 

3.90 

3.95 

3.96 

4.34 

4.90 

4.99 

5.04 

5.05 

5.10 

5.11 

5.16 

5.26 

5.33 

5.34 

5.36 

5.39 

5.41 

5.5 

5.51 

5.57 

5.64 

5.67 

5.7 

5.78 

5.83 

5.89 

5.95 

6.18 

6.31 

6.37 

6.84 

7.26

CaO

0.09 

.22 

.36 

.10

.94 

.09

.00 

.08 

1.12 

.00 

.00 

.60 

.00 

.10 

.68 

.90 

.00 

.36 

Tr. 

.00 

Tr. 

Tr. 

.13 

.00 

.24 

Tr. 

Tr.

.16 

.10 

.00 

.00 

Tr. 

.00 

.64 

.00 

Tr. 

.04 

.26 

Tr. 

.96 

.00 

Tr. 

.67 

Tr. 

.26 

.00 

Tr. 

.00 

Tr. 

.00 

Tr. 

.22

Tr. 

Tr.

Na2O

0.57 

1.10 

.78 

1.19 

.91 

.96 

.69 

1.05 

.64 

.59 

1.88 

.88 

.66 

.51 

.47 

.79 

.30 

.12 

.63 

.5 

.77 

1.27 

.87 

.64 

.13 

1.3 

.95 

.40 

.77 

2,17 

1.06 

.53 

.74 

.57 

.52 

.57 

.64 

.51 

.89 

1.10 

.66 

.59 

.52 

.56 

.63 

.72 

.59 

.06 

.35 

.65 

1.03 

.82 

.4 

.72 

.84 

.90 

.44 

.53

K2O

10.76 

10.20 

9.73 

10.71 

10.07 

9.31 

10.50 

8.92 

10.08 

10.52 

8.19 

9.95 

10.37 

8.90 

10.40 

10.16 

9.60 

10.21 

10.09 

9.46 

9.52 

10.32 

10.02 

9.91 

a 82 

10.06 

10.13 

10.13 

9.93 

8.03 

11.01 

8.62 

9.58 

10.14 

10.25 

9.53 

8.69 

10.55 

10.79 

10.97 

11.24 

10.14 

9.82 

9.75 

10.25 

10.18 

10.11 

10.37 

9.08 

9.90 

11.18 

9.70 

9.67 

10.28 

10.63 

11.10 

10.65 

11.05

RbsO

0.82

.79 

.53 

.93

1.20

.57 

1.1

.35 

1.3

1.37 

1.5 

1.93 

1.11 

.91 

1.55 

3.73 

1.5 

1.39 

1.17 

1.66 

2.44

3.8

1.56 

1.62 

1.78 

1.64

.42

.32

.97

2.0 

1.38

1.04

3.2

2.00

1.38 

1.97 

1.22

1.35 

1.14

CsaO

0.09

.06 

<.20 

.20

.20 

Tr. 

.3

.75 

.2

.41 

.2 

.18 

.13 

.16 

.11 

.08 

.2 

.17 

.62 

.12 

.72

1.08 

.48 

.09 

.19 

.17

.41

.06

.66

.48 

.05 

.67

.93

.08

.09 

1.2 

.24

.40 

None

H20-f

4.35 

4.36 

5.90 

3.6 

4.5 

6.85 

4.66 

3.85 

4.12 

4.81 

4.65 

4.48 

4.06 

6.84 

3.62 

3.41 

6.50 

5.96 

3.06 

3.32 

2.18 

2,15 

2.56 

2.18 

1.7 

1.64 

1.84 

2.6 

1.76 

l.S

1.46

1.28 

1.22 

1. 

1.02 

4.28 

1. 

1.24 

1.39 

.8 

.88 

3.25 

.57 

1.50 

2.96 

1.35 

3.94 

.79 

.90 

.4 

.8 

.38 

.58 

3.72 

.5 

.49 

.47

H2O0.55 

.60 

1.64 

8 

2 

4.09 

.79 

2.48 

.46 

.44 

.08 

.38 

.12 

3.06 

.10 

.69 

4.86 

2.36 

.34 

.32 

.26 

.27 

.54 

.18 

2 

.14 

.08 

4 

.14 

2 

95 

0.88 

.46 

.51 

21 

.31 

3.68 

!9 

.26 

.78 

7 

.66 

3.51 

.06 

.66 

3.68 

.30 

3.86 

.09 

.34 

4 

6 

.50 

.81 

.88 

9 

.74 

.73

F

0.62 

.79 

.66 

.73 

.20 

.37 

1.01 

1.00 

.91 

1.31 

.54 

.88 

.76 

.07 

1.21 

1.41 

1.02 

.05 

2.06 

2.82 

4.09 

5.98 

4.93 

4.97 

5.18 

4.60 

6.03 

5.21 

6.52 

5.45 

5.80 

6.69 

7.22 

7.49 

6.89 

6.86 

1.04 

7.65 

7.76 

6.75 

8.92 

7.65 

4.61 

6.86 

7.36 

5.23 

7.66 

5.93 

6.15 

8.08 

8.22 

7.13 

6.85 

9.19 

4.34 

8.26 

9.00 

7.73

Note and footnotes at end of table.
INTERPRETATION OF LITHIUM MICAS 143

TABLE 6. Analyses, with data for writing formulas, of aluminum lithium micas used in interpretation of composition Continued

[In order of increasing LijO content]

Analysis 1

1 ___ ..........

2 _ ..............

3.. ...............

4.................

5. 

6.. ...............

7.. ............ ...

8.. ............

9.................

10................

11. . 

12.. __ ..........

IS......... _ 

14... . _

15 _ - 

16.. ....... .

17 

18... _ _ _

19--.... ...... ....

20... ......

21........ .

22..... .. .....

23.. _ ...........

24 __ , ___ ......

25 

26. _ ...... . ...

27... ...........

28.... .........

29.......... . .

SO.. ...........

31_. ............ ..

32. .. ____ . . .

33...... .......

34 ... . ....

35................

36...... -.

37.-..-... . .

38 . 

39.... .........

40---.. _ ........

41. 

42-... ........

43.- ..........

44-. ..........

45

46.-.. .........

47.. _ .... ...

48.... ... _

49...... .......

50... __ . .....

51 ........ ......

52 ..

53-. ... _

64 . 

55. 

56 

57-- 

58 .. ........

Percent

Total

100.11 

100.30 

100.30 

101.06 

* 100. 39 

101. 11 

100.90 

100.13 

100.24 

100.51 

100.46 

100.66 

100.04 

100.85 

100.29 

100.63 

100.77 

100.71 

100.76 

101. 21 

102.06 

102. 95 

102. 16 

102.05 

102. 71 

102. 02 

102. 78 

102.62 

103. 27 

102. 52 

101. 89 

103. 15 

102. 78 

103. 19 

102. 82 

102.98 

< 99. 70 

103. 39 

102.98 

 102. 70 

103.50 

102. 51 

102. 17 

102.64 

102. 88 

100.54 

102. 95 

101.83 

102. 76 

103. 46 

103. 36 

100.23 

102. 96 

104. 16 

' 103. 10 

103. 55 

8 103. 72 

 103. 43

0~Fs

-0.26 

-.33 

-.24 

-.31 

-.08 

-.16 

-.42 

-.42 

-.38 

-.55 

-.23 

-.37 

-.32 

-.03 

-.51 

-.59 

-.43 

-.02 

-.87 

-1.19 

-1.72 

-2.52 

-2.08 

-2.09 

-2.18 

-1.94 

-2.54 

-2.19 

-2.75 

-2.29 

-2.44 

-2.82 

-3.04 

-3.15 

-2.90 

-2.89 

-.43 

-3.22 

-3.27 

-2.85 

-3.76 

-3.22 

-2.16 

-2.89 

-3.10 

-2.22 

 3.18 

-2.50 

-2.59 

-3.40 

-3.46 

-3.00 

-2.89 

-3.87 

-1.83 

-3.48 

-3.79 

-3.26

Adjusted 

total

99.85 

99.97 

100.06 

100.75 

100.31 

100.95 

100.48 

99.71 

99.86 

99.96 

100.23 

100.29 

99.72 

100.82 

99.78 

100.04 

100.34 

100.69 

99.89 

100.02 

100.34 

100.43 

100.08 

99.96 

100.53 

100.08 

100. 24 

100. 43 

100. 52 

100.23 

99.45 

100. 33 

99.74 

100.04 

99.92 

100. 09 

99.27 

100. 17 

99.71 

99.85 

99.74 

99.29 

100. 01 

99.75 

99.78 

98.32 

99.77 

99.33 

100. 17 

100. 06 

99.90 

97.23 

100.07 

100. 29 

101. 27 

100. 07 

99.93 

100.17

Octahedral positions occupied by 

Al

1.92 

1.94 

1.75 

1.88 

1.93 

1.81 

1.90 

1.68 

1.93 

1.90 

1.86 

1.86 

1.89 

1.60 

1.84 

1.71 

1.74 

1.73 

1.73 

1.69 

1.58 

1.52 

1.54 

1.54 

1.55 

1.54 

1.40 

1.49 

1.51 

1.44 

1.39 

1.21 

1.32 

1.29 

1.32 

1.36 

1.12 

1.16 

1.34 

1.26 

1.26 

1.10 

1.19 

1.36 

1.34 

1.40 

1.31 

1.10 

1.36 

1.30 

1.24 

1.25 

1.33 

1.10 

1.01 

1.26 

1.05 

.88

Ti

0.00 

.00 

.01

.00 

.00 

.01 

.00 

.00 

.00 

.01 

.00 

.02 

.00 

.00 

.02 

.01 

.00 

.00 

.00 

.00 

.00 

.00

.00 

.00 

.00 

.00

.00 

.00 

.00 

.00 

.00

.01 

.00 

.00

.01 

.00 

.00 

.00 

.01 

.00 

.01 

.00 

.00 

.00 

.00 

.00 

.00 

.02 

.00 

.00 

.02

Fe«

0.01 

.02 

.15 

.00 

.03

.05 

.01 

.14 

.00 

.01 

.01 

.00 

.01 

.25 

.00 

.07 

.05 

.03 

.00 

.00 

.01

.02 

.01 

.00

rto

rto

.08

.03

.04

.02

no

.02 

.02 

.00

.02

.02 

.01

.00

.02 

.00

.01

Fe+8

0.00 

.03 

.03 

.03

.07 

.00 

.09 

.00 

.00 

.00 

.08 

.00 

.04

.06 

.06 

.08 

.07 

.06 

.02 

.01 

.00 

.00 

.01 

.00 

.08 

.02 

.00 

.00

.09 

.01 

.01 

.01 

.01

.11 

.00 

.07

.15 

.01 

.00 

.00 

.01 

.00 

.01 

.00 

.00 

.00 

.01 

.00 

.01

.01 

.02

Mg

0.01 

.00 

.03 

.04

.02 

.05 

.11 

.01 

.00 

.00 

.01 

.00 

.02 

.03 

.02 

.01 

.03 

.01 

.00 

.01 

.00 

.00 

.00 

.00 

.00 

.04 

.00 

.01

.00 

.00 

.01 

.00 

.00 

.00 

.17 

.00 

.00 

.01 

.07 

.00 

.09 

.00 

.00 

.03 

.00 

.13 

.00 

.01 

.03 

.01 

.02 

.03 

.13

.02 

.03

Mn«

0.05 

.00

.00 

.04

.02

.01 

.02 

.01 

.01 

.00 

.00 

.00 

.01 

.00 

.00 

.02 

.02 

.12 

.03 

.05 

.02 

.00 

.02 

.03 

.07 

.04 

.03 

.02 

.04 

.03 

.16 

.14 

.01 

.00 

.12 

.01 

.04 

.05 

.15 

.08 

.03 

.01 

.07 

.02 

.11 

.01 

.03 

.08 

.04 

.02 

.12 

.01 

.04 

.04 

.00

Li

0.02 

.02 

.07

.08 

.10 

.12 

.11 

.13 

.13 

.17 

.18 

.20 

.20 

.23 

.29 

.30 

.44 

.42 

.48 

.66 

.73 

.94 

1.00 

1.01 

1.03 

1.04 

1.05 

1.06 

1.06 

1.16 

1.29 

1.39 

1.35 

1.38 

1.39 

1.35 

1.40 

1.43 

1.44 

1.45 

1.45 

1.50 

1.50 

1.47 

1.49 

1.41 

1.52 

1.62 

1.53 

1.56 

1.55 

1.61 

1.59 

1.68 

1.67 

1.68 

1.84 

1.93

Total

2.01 

2.01 

2.04 

2.07 

22.07 

2.07 

2.09 

2.16 

2.08 

2.10 

2.06 

2.17 

2.10 

2.16 

2.16 

2.17 

2.32 

2.30 

2.31 

2.43 

2.47 

2.50 

2.59 

2.57 

2.61 

2.61 

2.60 

2.64 

2.62 

2.65 

2.72 

2.81 

2.72 

2.84 

2.86 

2.73 

2.72 

2.87 

2.79 

2.85 

2.86 

2.93 

2.89 

2.86 

2.84 

2.95 

2.85 

3.00 

2.91 

2.90 

2.90 

2.92 

2.96 

2.94 

2.86 

2.98 

2.96 

82.93

Octahedral 

charge

-0.07 

-.04

-.07 

-.06 

+.01 

-.12

-.02 

+.03 

-.04 

-.06 

-.19 

+.02 

-.10 

-.02 

-.13 

-.18 

+.03 

-.04 

-.13 

-.11 

-.20 

-.42 

-.28 

-.33 

-.20 

-.27 

-.45 

-.29 

-.31 

-.40 

-.44 

-.48 

-.59 

-.41 

-.35 

-.53 

-.81 

-.47 

-.52 

-.47 

-.44 

-.50 

-.51 

-.39 

-.47 

-.07 

-.51 

-.48 

-.34 

-.46 

-.51 

-.52 

-.34 

-.70 

-.88 

-.46 

-.87 

-1.02

Tetrahedral 

charge

-0.95 

-1.00 

-.95 

-1.02 

 1.02 

-1.00 

-.98 

-.98 

-.97 

-.94 

-.94 

-.97 

-.91 

-.97 

-.84 

-.87 

-1.02 

-1.02 

-.89 

-.88 

-.84 

-.69 

-.74 

-.66 

-.71 

-.78 

-.62 

-.70 

-.72 

-.68 

-.62 

-.60 

-.42 

-.62 

-.67 

-.41 

-.12 

-.49 

-.55 

-.62 

-.68 

-.52 

-.60 

-.61 

-.56 

-.92 

-.49 

-.49 

-.64 

-.57 

-.57 

-.52 

-.68 

-.33 

-.15 

-.53 

-.17 

-.06

Composite 

layer 

charge

-1.02 

-1.04 

-1.02 

-1.08 

-1.01 

-1.12 

-1.00 

-.95 

-1.01 

-1.00 

-1.13 

-.95 

-1.01 

-.99 

-.97 

-1.05 

-.99 

-1.06 

-1.02 

-.99 

-1.04 

-1.11 

-1.02 

-.99 

-.91 

-1.05 

-1.07 

-.99 

-1.03 

-1.08 

-1.06 

-1.08 

-1.01 

-1.03 

-1.02 

-.94 

-.93 

-.96 

-1.07 

-1.09 

-1.12 

-1.02 

-1.11 

-1.00 

-1.03 

-.99 

-1.00 

-.97 

-.98 

-1.03 

-1.08 

-1.04 

-1.02 

-1.03 

-1.03 

-.99 

-1.04 

-1.08

Interlayer cations

Charge

+1.00 

+1.05 

+1.02 

+1.06 

+1.00 

+1.12 

+1.00 

+.95 

+.99 

+.99 

+1.15 

+.99 

+1.01 

+.96 

+.98 

+1.06 

+1.03 

+1.05 

+1.02 

+1.03 

+1.01 

+1.10 

+1.01 

+.99 

+.94 

+1.08 

+1.09 

+.98 

+1.02 

+1.09 

+1.08 

+1.06 

+.99 

+1.03 

+1.03 

+.94 

+.93 

+.98 

+1.06 

+1.C9 

+1.10 

+.99 

+1.08 

+1.00 

+1.03 

+1.00 

+1.00 

+.99 

+.98 

+1.02 

+1.08 

+1.02 

+.99 

+1.04 

+1.03 

+1.05 

+1.04 

+1.05

Positions

1.00 

1.03 

.99 

1.06 

1.00 

1.05 

.99 

.95 

.99 

.98 

1.07 

.99 

1.01 

.91 

.98 

1.05 

.98 

.98 

1.02 

1.01 

1.01 

1.10 

1.01 

.99 

.93 

1.08 

1.08 

.98 

1.02 

1.09 

1.07 

1.05 

.99 

1.03 

1.03 

.94 

.88 

.98 

1.06 

1.09 

1.08 

.99 

1.01 

1.00 

1.03 

.95 

1.00 

.97 

.98 

1.02 

1.08 

1.02 

.99 

1.04 

1.02 

1.05 

1.04 

1.05

The numbers in the footnotes below are in percent.

i See descriptions on page 144 for origin of samples and source of analyses.

8 Includes 0.21 MntOs, oO.Ol octahedral position.

»Total Fe reported as FeO.

« Includes 0.09 PsOi and 0.34 SO3.

»Includes 0.05 Cl.

11 May be present as FezOs.

1 1ncludes 0.04 P2 O5 , 0.34 SO3, and 0.02 Cl.

»Includes 0.14 NbzOj, oO.OO octahedral position.

 Includes 1.52 NbzOs, O0.04 octahedral position.

(Notes to table 6 are on page 144)
144 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

NOTES TO TABLE 6

1. Apache, Petaca, N. Mex. (Heinrlch andlLevinson, 1953, p. 43, no. 4).

2.

3.

4.

5.

, , . . , , 

Russia, locality not given (Ginzburg and Berhkin, 1953, p. 95).

Yamanoo, Tsukuba, Japan (Shibata, 1952b, p. 163, no. o12). 

Londonderry, Western Australia (Simpson, 1927, p. 46).

Harding mine, 9}i miles east of Embudo, N. Mex. (Wells, 1937), p. 108, B. Corrections of percentages of alkalies by Stevens and Schaller, 1942, p. 527.

6. Yamanoo, Tsukuba, Japan (Shibata, 1952b, p. 163, no. 11).

7. White Spar mine No. 1, Gunnison County, Colo. (Heinrich and Levinson, 1953, 

p. 43, no. 2).

8. Kimito, southwest Finland (Pehrman, 1945, p. 56).

9. Pittlite, Rociada, N. Mex. (Heinrich and Levinson, 1953, p. 43, no. 5).

10. Brown Derby No. 1 mine, Gunnison County, Colo. (Heinrich and Levinson, 

1953, p. 43, no. 3).

11. Varutrask, Sweden (Berggren, 1940, p. 183, H.). Normal muscovite structure.

12. Varutrask, Sweden (Berggren, 1940, p. 183, G). Normal muscovite structure.

13. Varutrask, Sweden (Berggren, 1941, p. 264, J). Normal muscovite structure.

14. Nagatare, Fukuoka Pref., Japan (Shibata, 1952b, p. 164, no. 19).

15. Varutrask, Sweden (Berggren, 1940, p. 185, F).

16. Varutrask, Sweden (Berggren, 1941, p. 264, L). Normal muscovite structure.

17. Bunsen mine, South Kankyo-nand5, Korea (Shibata, 1952b, p. 164, no. 21).

18. Bunsen mine, South Kankyo-nandS, Korea (Shibata, 1952b, p. 164, no. 22).

19. Varutrask, Sweden (Berggren, 1940, p. 185, E). Normal muscovite structure.

20. Varatrask, Sweden (Berggren, 1940, p. 185, D). Normal muscovite structure.

21. Manitoba, Canada (Stevens, 1938, p. 615, no. 1, U.S. Natl. Mus. No. 97635). 

Normal muscovile structure.

22. Katerina mine, Pala, San Diego County, Calif. (Stevens, 1938, p. 615, no. 2). 

Transitional structure (combination of forms).

23. Stewart mine, "40 acres," Pala, San Diego County, Calif. (Stevens, 1938, p. 615, 

no. 3). Transitional structure (combination of forms).

24. Panama-Paciflc-Expo"ition mine, Chihuahua Valley, east of Oak Grove, San 

Diego County, Calif. (Stevens, 1938, p. 615, no. 4). Transitional structure 

(combination of forms).

25. Norway, Maine (Clarke, 1910, p. 287, F).

26. Varutrask, Sweden (Berggren, 1940, p. 185. C). Normal muscovite structure.

27. Rozna, Moravia, Czechoslovakia (R. E. Stevens written communication, 1938, 

U.S. Geol. Survey Lab. Record No. D-789).

28. Mt. ApaHte, Auburn, Maine (Winchell, 1942, p. 115, no. 17, U.S. Natl. Mus. 

No. 80230).

29. Stewart mine, San Diego County, Calif. (Stevens, 1938, p. 615, no. 5). Transitional structure (combination of forms).

30. Auburn, Maine (Clarke, 1910, p. 287, D).

31. Black Mountain, Rumford, Maine (Clarke, 1910, p. 287, A).

32. Kimito, southwest Finland (Pehrman, 1945, p. 59).

33. Stewart mine, Pala, San Diego County, Calif. (Stevens, 1938, p. 615, no. 6). 

Structure, 6-layer lepidclite.

34. Ohio City, Colo. (Stevens, 1938, p. 615, no. 7. U.S. Natl. Mus. No. 97893). 

Structure, 6-layer lepidolite.

35. Ohio City, Colo. (Winchell, 1942, p. 115, no. 10).

36. Himalaya mine, Mesa Grande, San Diego County, Calif. (Stevens, 1938, p. 615, 

no. 8). Structure, 1-layer lepidolite.

37. Locality not given (Shilin, 1953. p. 155).

38. Wakefleld, Quebec, Canada (Winchell, 1942, p. 115, no. 26).

39. San Diego mine, Mesa Grande, San Diego County, Calif. (Stevens, 1938, p. 615, 

no. 9). Structure, 1-layer lepidolite.

40. Alabaschta, Urals (Winchell, 1942, p. 115, no. 18).

41. New Ross, Nova Scotia (Walker and Parsons, 1924, p. 49).

42. Wakefleld, Quebec, Canada (Stevens, 1938, p. 615, no. 10). Structure, 1-layer 

lepidolite.

43. Uruchin, Kogen-d6, Korea (Shibata, 1952b, p. 165, no. 25).

44. Roezna, Moravia (Berggren, 1941, p. 271, no. 1).

45. Slewart mine, Pala, San Diego County, Calif. (Stevens, 1938, p. 615, no. 11). 

Structure not determined.

46. Yagatare, Fukuoka Pref., Japan (Shibata, 1952b, p. 164, no. 20).

47. Stewart mine, Pala, San Diego County, Calif. (Stevens, 1938, p. 615, no. 12). 

Structure, 6-layer lepidolite.

48. Bunsen mine. South Kanky5-nand5, Korea (Shibala, 1952a, p. 150).

49. Uto, Sweden (Berggren, 1941, p. 269).

50. Himalaya mine, Mesa Grande, San Diego County, Calif. (Stevens, 1938, p. 615, 

no. 13). Structure, 1-layer lepidolite.

51. Londonderry, Western Australia (Simpson, 1927, p. 46).

52. Calgoorie, Western Australia (Stevens, 1938, p. 615, no. 14). Structure, 3-layer 

hexagonal lepidolite.

53. Varutrask, Sweden (Berggren, 1940, p. 185, A). Structure, 6-layer lepiaolite.

54. Little Three mine, Ramona, San Diego County, Calif. (Stevens, 1938, p. 615, no. 

15). Structure, 1-layer lepidolite.

55. Locality not given (Shilin, 1953, p. 155, no. 2).

56. Londonderry, Western Australia (Simpson, 1927, p. 46, no. III).

57. Antsongombato, Madagascar (Stevens, 1938, p. 615, no. 16). Structure, 1-layer 

lepidolite.

58. Kangerdluarsuk, Julianehaab district, Greenland (Stevens, 1938, p. 616, no. 17, 

U.S. Natl. Mus. No. 94314). Structure, 1-layer lepidolite.

TABLE 7. Analyses, with data for writing formulas, of siderophyllites and ferrous lithium micas used in interpretation of composition

[In order of increasing Li^O content]

Analysis '

1.. ___ ..... _ ..... _ . _

2.. __ ........... _ 

3- .........................

4.... .. _ _ .

5. ...... _ ............

6... . _ ..................

7 .

8. ...................-.-.

9 ........ ___ .. __ ......

10........-............. ..

11 ....... _ . __

12 

13.... _ ....................

14.................... ..

15 .. __ _ ._.._ . 

16 - . ..... 

17 

18 ... _ ....

19 _ . . . 

20 ___ .

21.. ...__ 

22 ___

23... . . . 

24.. . .. ___ ..... _____

25 . .. _

26..- _ ........

27 ___ . . ...

28 _ . . . 

29. .....

30 

31 __ ...

32. ___ ... _____ ....

33. ......

34 

35 

Si02

39.60

33.60

35.25

31.96

38.00

38.00

38.64

36.91

43.70

37.12

48.26

41.78

38.83

36.51

AK OO

46.44

48.42

39.04

46.37

42.62

43.50

43.20

46.80

46.74

45.88

41.60

48.40

45.98

51.46

51.96

52.17

A12 03

22.80

22.36

17.24

14.99

17.06

20.96

23.63

27.00

19.91

18.20

22.96

22.37

20.73

22.76

22.27

18.37

21.78

21.84

20.02

23.56

23.45

23.61

25.00

23.34

24.50

21.78

20.80

25.70

21.62

18.04

16.22

16.89

16.39

TiOj

0.21

.06

.21

1.51

.76

.08

1.62

.64

.55

.32

Tr.

.12

.14

.16

.57

1.30

Tr.

1.35

1.33

.76

.22

Fe2Os

0.79

1.44

8.15

7.73

7.44

2.87

4.84

3.98

5.18

.59

7.81

.21

.98

4.40

10.06

.66

.47

1.41

.32

6.10

.50

1 19

.97

.24

3.56

2.21

2.63

FeO

20.98

28.54

17.83

20.61

OO J.1

24.12

18.69

18.50

19 33

21.97

11.67

12.03

10.20

14. 24

9.07

12.22

11.66

U

ne

10.06

7.98

12.42

10.06

8.58

11.80

1O flrt

fi OK

10 22

7 19

6.00

7.63

6.32

5 QQ

MgO

O dfi

.10

.70

.28

.62

.29

1 1Q

.12

97

.20

2 9ft

.55

.38

.63

00

97

.21

QQ

.14

.20

nn

.13

.12

1.60

.17

.03

Tr.

MnO

0.29

.33

91

.89

.74

.71

.24

.64

1.59

.29

1 Qfi

3.21

.68

1.66

1.97

1.75

1.73

1 89

.37

.35

4.02

.73

7*>

1.38

.37

1.74

.22

1 97

2.46OR

OO

Percent

Li2O

0.32

.39

.48

.50

.59

1.19

1.29

1.44

1.47

1.48

1.92

2.10

2.31

2.42

2.62

2.70

3.28

3.23

3.36

3.27

3.39

3.40

3.41

3.70

3 7ft

3.73

3 79

3.78

4.03

4.18

4.57

4.81

4.87

4 QQ

CaO

1.52

.14

.73

1.10

.35

.48

.48

1.30

.28

.23

1.05

1.14

.99

.97

.78

.50

.32

.42

45

.24

.00

.30

.06

1.80

Tr.

.12

Tr.

Na8O

Tr.

0.46

.21

.27

.44

.51

1.01

1.08

1.37

68

.28

.74

.81

1.10

.67

.48

.18

.42

.78

2.45

1.27

.82

1.20

1.38

1.73

54

no

2.20

.25

SQ

.87

.63

K2O

8.95

8.90

8.53

7.21

7.68

7.41

8.64

9.40

8.15

9.68

8.22

9.58

8.60

10.47

10.51

9.53

8.99

9

QQ

6.35

8.51

8.57

9.41

7.73

7.66

9.20

10.37

9.11

8.03

10.45

9.91

10.48

H2 0+

2.93

1.66

3.17

2.99

3.62

5.66

3.

.98

3.00

1.

4.

1.35

2

.60

1.4 H8O2.93

O

Q7

2.27

3.

3.60

1.96

4.05

4.60

.8

8

1.42

4.40

64

.86

1

1.

1.

H2O0.24

.08

3.21

2.78

2.20

2.94

31

KA

.04

59

51

.08

13

.40

1

H2 0+

3.74

31

.54

25

.27

.76

.55

1.29

8

Q

.86

.24

1.14

12

31

i6

F

2.03

.89

2.36

1.67

1.97

1.59

3.80

1.66

5.76

3.15

5.52

.21

5.40

6.48

3.82

4.79

7.94

7.98

7.62

6.12

2.55

2.78

1.28

1.28

8.63

7 54

5.12

1.58

2.24

5.66

7.44

6.78

7.02

Total

100.80

» 98. 91

99.22

100.43

100.53

100.84

» 98. 17

* 100. 72

101. 86

103. 38

101. 17

 101.53

99.64

 101. 04

101.80

100.99

104. 22

' 105. 53

103.63

103. 74

99.24

99.30

102. 44

100.33

101. 45

101. 76

103. 94

103. 36

99.56

101. 25

» 100. 83

101. 95

102. 66

102. 72

103. 56

Note and footnotes at end of table.
INTERPRETATION OF LITHIUM MICAS 145

TABLE 7. Analysis, with data for writing formulas, of si derophyllites and ferrous lithium micas used in interpretation of composition 

Continued

[In order of increasing LizO content]

Analysis '

1.... ___________ .....

2 _ . ____________ ....

3 _ _ . 

4 _____________ . _ ..

5 ___________ . ___

6..... ..-_._.._ .-

7 _______________ ...

8. _____ . __ . _____

9. ______ . __ ..... _ __

10... __ . . 

11 _______________ .

12 _____ ..... _ . _ . __

13.. _ ... 

14... _________ .... _ ..

15 _____ . _____ ........ 

16. ____ ......... ___

17.......... ..............

18- ......................

10

20... ___ .... _ . _ .......

21 _____ . ___ . ______ .

23....... ....................

24... ___ . _ ..... __ ...... 

25... ... _ ... __ ........... 

26. ____ .. _ .............. 

27 ........ ................ 

28. ...... ...............

29.. ___ . _ . _______ .... 

30........................... 

31.............. __ ... _ .. 

32........................... 

33...-. ...-...............

34...... .....................

35__. __ _____ _ ... _ ..

Percent

O=F,

-0.85 

-.37 

-.99 -.70

-.84 -.67

-1.60 

-.70 

-2.42 

-1.33 

-2.32 

-.09 

-2.27 

-2.72 

-1.61 

-2.02 

-3.34 

-3.36 

-3.21 

-2.58

-1.07 

-1.17 

-.54 

 54 

-3! 63 

-3.17 

-2.16 

-.67 

-1.04 

-2.38 

-3.13 

-2.85 

-2.96

Adjusted 

total

99.95 

98.54 

98.23 

99.73 

99.69 

100. 17

99.12 

101. 16 

100. 96 

99.84 

99.21 

99.55 

98.77 

99.08 

99.38 

102.20 

102. 19 

100.27 

100.53 

96.66

101. 37 

99.16 

100. 91 

101. 22 

100. 31 

100. 19 

97.40 

100. 58 

99.79 

99.57 

99.53 

99.87 

100.60

Octahedral positions occupied by 

Al

0.99 

.73 

.52 

.44 

.36 

.39 

.72 

.94 

1.06 

.71 

.57 

1.13 

.65 

1.16 

1.04 

.95 

.50 

1.08 

1.05 

1.05 

1.15 

.80 

1.10 

1.04 

1.08 

1.01 

1.23 

1.08 

1.04 

1.09 

1.11 

.77 

.91 

.94 

.90

Ti

0.01 

.00 

.01 

.09 

.05 

.00 

.09

.03

.03

.02 

.00

.01 

.01

.01 

.03 

.07 

.00 

.07 

.07

.04 

.01

Fe+>

0.05 

.08 

.62 

.49

.47 

.47 

.16 

.27

.23

.31 

.03 

.43 

.01 

.05 

.25 

.58 

.04 

.02 

.07 

.02 

.33

.06

.03 

.06

.05

.01 

.19 

.12 

.14 

.21

Fe«

1.32 

1.88 

1.22 

1.38 

1.51 

1.70 

1.19 

1.01 

1.12 

1.24 

1.44 

.71 

.74 

.61 

.87 

.58 

.79 

.68 

.68 

.59 

.48 

.75 

.61 

.51 

.69 

.75 

.37 

.60 

.58 

.68 

.42 

.36 

.44 

.36 

.34

Mg

0.05 

.01 

.09 

.03 

.08 

.04 

.14

.01 

.03 

.02

.24

.06 

.04 

.07

.02

.10 

.02 

.10 

.01 

.02

.01 

.01

.16 

.02 

.00 

.00

Mn«

0.02 

.02 

.02 

.06 

.05 

.05

.02 

.04 

.10 

.02 

.12 

.20 

.04

.11 

.13 

.10 

.10 

.11 

.02

.02 

.24 

.04 

.04 

.08 

.02 

.10 

.01 

.12 

.14 

.00 

.01 

.02

Li

0.10 

.13 

.15 

.16 

.20 

.37 

.39 

.42 

.45 

.47 

.56 

.62 

.66 

.71 

.80 

.84 

.92 

.92 

.95 

.94 

.98 

.94 

.98 

1.04 

1.06 

1.04 

1.05 

1.09 

1.15 

1.16 

1.30 

1.35 

1.36 

1.38

Total

2.44 

2.82 

2.61 

2.64 

2.68 

2.85 

'2.68 

2.63 

2.68 

2.76 

2.86 

2.57 

2.88 

2.48 

2.73 

2.74 

2.92 

2.82 

2.79 

2.77 

2.62 

2.99 

2.76 

2.93 

2.93 

2.95 

2.75 

2.81 

2.87 

2.98 

2.82 

2.93 

2.84 

2.81 

2.85

Octahedral 

charge

-0.06

+.35 

+.25 

+.24 

+.13 

+.36 

+.05 

+.08 

+.06 

+.01 

+.19

+.22 -.53

-.16 -.10

+.10 -.16

OQ

-.51

+.19 

-.18 

-.02 

+.04 

-.01 

-.28 -.29

-.26 

-.02 

-.40 

-.46 

-.64 -.66

Tetrahedral 

charge

1 AD

-1.35

1 ^O

-1.19 

-1.06 

-1.31 

-1.16 

-1.15 

-1.24

-1.06

-1.11

QQ

1 28

-.57

-.93 

-1.05

-1.18

70

7ft

7^

-.54

-1.20 

-.80 

-.95 

-.97 

-.94 

-.77 -.72

-.72 

-1.05 

-.65 

-.74 

-.42 

-.42 -.42

Compositelayer 

charge

1 AQ

-1.00 

-1.07

OK

-.93 -.95

-1.11 

-1.07

-1.18 

-1.08

-.92 

-1.05

-1.06 

-1.10

-1.09 

-1.15 

-1.08 -.95

-1.05 

-1.04

-1.05

 1. Ul

-.98 

-.97 

-.93 

-.95 

-1.05 

-1.01

-.98 

-1.07 

-1.05 

-1.20 

-1.06 

-1.08 -.99

Interlayer cations

Charge

+1.10 

+.99 

+1.06 

+.96 

+.92 

+.96 

+1.07 

+1.06 

+1.15 

+1.08 

+.90 

+1.04 

+1.08 

+1.07 

+1.08 

+1.19 

-1.08 

+.94 

+1.01 

+1.02 

+1.07 

+1.03 

+1.00 

+1.02 

+.91 

+.95 

+1.08 

+1.00 

+.96 

+1.07 

+1.07 

+1.20 

+1.07 

+1.07 

+1.00

Positions

0.98 

.98 

.99 

.87 

.89 

.92 

1.03 

1.06 

1.04 

1.06 

.89 

1.04 

1.00 

1.07 

1.08 

1.08 

1.00 

.94 

1.01 

1.02 

.99 

.97 

.96 

.99 

.88 

.91 

1.08 

1.00 

.96 

1.05 

1.07 

1.07 

1.07 

1.06 

1.00

The numbers in the footnotes below are in percent.

1 See descriptions below for origin of samples and source of analyses.

> Contains 0.03 PjOj.

» Contains 0.32 SnO2 (oO.Ol octahedral position), and 0.60 undissolved residue.

* Contains 0.75 B2 O».

 Contains 1.04 Rb2 O and 0.10 CssO. 

« Contains 0.68 B2 O3 . 

» Contains 0.08 PsOs. 

s Contains 2.48 B2O3 .

NOTES TO TABLE 7

New Castle, Ireland (Nockolds and Richey, 1939, p. 39). In greisen veins cutting 17.

aplite veins in granite. 18.

Yagenyama, Japan (Shibata, 1952b, p. 162, no. 7). In topaz vein in granite 19.

pegmatite. 20.

Ebisu mine, Naegi District, Japan (Shibata, 1952b, p. 162, no. 6). In greisen. 21.

Hachiman, Naegi District, Japan (Shibata, 1952b, p. 161, no. 1). In granite 22.

pegmatite. 23.

Hachiman, Naegi District, Japan (Shibata, 1952b, p. 161, no. 2). In pegmatite. 24.

Hachiman, Naegi District, Japan (Shibata, 1952b, p. 161, no. 3). In pegmatite. 25.

Wilzschhaus, Germany (Stelzner, 1896, p. 391). From granite. 26.

Lingwu, Hunan, China (Meng and Cbang, 1935, p. 57). In pneumatolytie- 27.

metamorphosed rocks (greisen).

Volhynia, Russia (Tsyganov, 1954, p. 386, no. 9). From topaz pegmatite. 28,

Zinnwald, Erzegebirge, Bohemia (Kunitz, 1924, p. 413). 29, 

Volhynia, Russia (Buryanova, 1940, p. 532-533). From granite pegmatite.

Morefield mine, Amelia, Va. (Wells, 1937, p. 113). 30,

Near Jundai, northwest of SSo Paulo, Brazil (Saldanha, 1946, p. 49). In quartz 31.

veins in gneiss, microgranitic quartz-porphyry, and greisen.

Lingwn, Hunan, China (Meng and Cbang, 1935, p. 57). In pneumatolytie- 32.

metamorphosed rock (greisen). 33.

Altenburg, Saxony, Germany (Kunitz. 1924, p. 413, no. 7). 34.

Yamanota, Naegi District, Japan (Shibata, 1952b, p. 162, no. 5). In pegmatite. 35.

Hachiman, Naegi District, Japan (Shibata, 1952b, p. 161, no. 4). In pegmatite.

Zinnwald, Erzegebirge, Bohemia (Dana, 1892, p. 626, no. 1).

Zinnwald, Erzegebirge, Bohemia (Kunitz, 1924, p. 413).

Zinnwald, Erze?ebirge, Bohemia (Dana, 1892, p. 626, no. 2).

Volhynia, Russia (Litvin, 1956, p. 120, no. 15). From pegmatite.

Eibenstock, Erzegebirge, Bohemia (Stelzner, 1896. p. 391).

Volhynia, Russia (Tsyganov, 1954, p. 386, no. 1). From pegmatite.

Locality not given (Ginzburg and Berhkin, 1953, p. 105).

Volhynia, Russia (Litvin, 1956, p. 120, no. 10). From pegmatite.

Volhynia, Russia (Litvin, 1956, p. 120, no. 9). From pegmatite.

Cassiterite Creek, Cape York, Alaska (Clarke, 1910, p. 287, no. M). W. T.

Scballer, analyst.

Zinnwald, Erzegebirge, Bohemia (Winchell, 1942, p. 115, no. 24). 

Anataboko, Madagascar (Duparc, Wunder, and Sabot, 1910, p. 369). From

pegmatite.

Volhynia, Russia (Tsyganov, 1954, p. 386, no. 2). From pegmatite. 

Lingwu, Hunan, China (Meng and Chang, 1935, p. 66). In pneumatolyticmetamorphosed rock (greisen).

Sakihama, Okirai, Iwate Pref., Japan (Shibata, 1952b, p. 162, no. 17). 

Cape Ann, Rockport, Mass. (Clarke, 1886, p. 358, no. B). R. B. Riggs, analyst. 

Cape Ann, Rockport, Mass. (Clarke, 1886, p. 358, no. A). R. B. Riggs, analyst. 

Cape Ann, Rockport, Mass.(Clarke, 1886. p. 358, no. C). R. B. Riggs, analyst.
146 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

TABLE 8. Analyses, with data for writing formulas, of ferrous lithium micas not used in interpretation of composition

[In order of increasing LijO content]

Analysis :

Percent

SiO» AljOj TiOj FejOj FeO MgO MnO LisO CaO NajO K»O H,0+ HiO- Total

7 

8...

9 

10 

11 

12.. 

13- 

14..

32.53

37.65

37.83

47.00

35.20

35.80

47.10

41.78

45.80

41.10

43.00

45.24

46.58

43.50

17.90

16.80

24.35

25.75

20.30

19.80

24.80

21.46

21.21

25.22

24.65

18.40

24.10

25.00

0.88

1.10

.30

1.40

1.60

1.64

.80

.57

Tr.

.80

.71

.19

4.45

.32

7.59

.26 

2.78

1.35

1.06 

.69

30.93

22.26

11.78

11.50

26.50

27.80

12.30

15.36

6.18

14.10

11.60

9.95

4.28

11.80

0.13

2.91

.44

.21

.16

.30

.15

.47

.57

.05

.05

.14

0.49 

.39 

.27 

.64 

.53

4.80 

.75

.63 

1.34 

.73

0.77

1.21

1.73

1.85

2.01

2.02

2.30

2.45

2.59

2.74

2.86

3.51

3.56

3.70

0.20

1.36

.20

.24

.17

1.75

.22

2.71

.72

.20

1.18

1.25

.68

.42

0.10

3.57

2.24

1.77

2.30

2.28

1.60

2.64

1.29

1.86

2.28

2.78

.84

1.20

7.19

6.54

10.03

5.35

8.70

5.85

6.26

6.12

8.89

9.80

9.01

7.63

10.81

7.73

3.57 

2.17

1.23 

4.20 

2.80 

3.00 

4.47 

1.91 

.44 

4.05 

3.90 

2.09

1.50 

4.05 I

0.28

.30 

.23 

.24 

.38 

.09 

.15 

.36

.55

1.21

4.28

4.28

3.09

1.66

1.66

3.33

5.95

5.78

2.95

2.58

6.32

7.90

1.28

100.35 

100.84 

102.27 

103.41 

102.21 

102.20 

103.56 

102.30 

»103.47 

103.71 

101.97 

99.69 

102.77 

101.45

Percent Octahedral positions occupied by 

O=F,

-0.51

-1.80

-1.80

-1.30 -.70

-.70

-1.40

-2.50

-2.43

-1.24

-1.09

-2.66

-3.33 -.54

Adjusted 

total

Al

99.84

99.04

100.47

102.11

101.51

101.50

102.16

99.80

101.04

102.47

100.88

97.03

99.44

100.91

0.49

.46

.86

1.28

.53

.50

1.24

.90

1.00

1.06

1.11

.92

1.24

1.08

Ti Fe« Fe« Mg Mn« Li Total

0.06 

.06 

.02 

.07 

.09 

.09 

.04 

.03 

.00 

.04 

.04 

.01

.07

0.03 

.02 

.42

2.16

1.44

.72

.66

1.70

1.77

.71

.94

.36

.84

.69

.61

.25

.69

0.01 

.34 

.05 

.02 

.02 

.03 

.01 

.02 

.06 

.00 

.00 

.03 

.05 

.01

0.03 

.02 

.02 

.04 

.03

.05 

.29 

.04

.04 

.08 

.04

0.26 3.04

2.72

2.60

2.58

2.99

3.01

2.64

2.67

2.59

2.77

2.65

2.71

2.66

2.93

Octahedral 

charge

+0.46

-.34 

+.01 

+.07 

+.07 

+.08 -.04

-.41

-.40

-.12

-.32

-.62

-.40 

+.04

Tetrahedral 

charge

-1.28

-1.08

-1.24

-.79

-1.30

-1.28

-.76

-.95

-.77

-1.07 -.95

-.68

-.75

-.97

Composite 

layer 

charge

-0.82

-1.42

-1.23 -.72

-1.23

-1.20 -.80

-1.36

-1.17

-1.19

-1.27

-1.30

-1.15

Interlayer cations

Charge Positions

+0.82 

+1.41 

+1.28

+.74 

+1.22 

+1.19

+.80 

+1.37 

+1.18 

+1.18 

+1.31 

+1.31 

+1.17

+.91

0.80

1.30

1.26

.72

1.19

1.05

.78

1.16

1.12

1.15

1.22

1.21

1.12

i See descriptions below for origin of samples and source of analyses. 

z Contains 2.04 percent (Rb,Cs)jO.

NOTES TO TABLE 8

1. Volhynia, Russia (Buryanova, 1940, p. 522-523).

2. Volhynia, Russia (Litvin, 1956, p. 120, no. 5). From pegmatite.

3. Gayer, Saxony, Germany (Dana, 1892, p. 627, no. 2).

4. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 3). From pegmatite.

5. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 10). From pegmatite.

6. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 11). From pegmatite.

7. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 6). From pegmatite.

8. Volhynia, Russia (Litvin, 1956, p. 120, no. 7). From pegmatite.

9. Minagi, Okayama Pref., Japan (Ukai, Nishimura, and Hashimoto, 1956, p. 32 

no. 2).

10. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 8). From pegmatite.

11. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 4). From pegmatite.

12. Volhynia, Russia (Litvin, 1956, p. 120, no. 14). From pegmatite.

13. New Ross, Nova Scotia (Walker and Parsons, 1924, p. 49). From pegmatite.

14. Volhynia, Russia (Tsyganov, 1954, p. 386, no. 5). From pegmatite.
INDEX

Page 

Aluminlan lepidomelanes___ ..______________ 130,131,132,134,138

lithium micas.___._._____.___.._.___..._._.__ 124,129 

Aluminum lithium micas....______... 115,116,117,120,121,122,124,126,138,140

and ferrous lithium micas, relation____________.________ 137 

Anionic composition of micas__________________________ 116 

Annite.._______._____._________.___.___.....___ 134

Berggren, Thelma.. __ ____.________.____._ 125

Berkhin, 8.1. See Ginzburg, A. I. and Berkhin, S. I.

Biotite...___..._.___......___...._._._._.__.. 115,116,128,140

Biotite-lepidolite series___________._________________ 127,128

Clarke, F. W..._____..........___._.___....________._.... 136

Compositional changes shown by the analyses_____________.__ 117,129

relations in siderophyllites and ferrous lithium micas___________ 130

Compositions, previous interpretations_____________________ 127

Cooke, J. P. Jr.._______....__.._.._....._________.. 127,136,140

Cryophyllite.._______________........_.___ 127,128,129,136,137,140

Cryophyllite-zinnwaldite relation________________________ 137

Dana, E. S.................._._.__._____...___...____ 127,129,136

Dioctahedral mica._______..._______________________ 119 

potassium micas._______.____. ________________ 115,120

Fe«-Li replacement ratios__ _______________________ 131 

Ferrian siderophyllites-.________________________.__ 130,134 

Ferroan lepidolites____________________________ 135,136,140 

Ferrous lithium micas...__. ...___.__ 115,116,127,128,129,130,131,132,135 

siderophyllites, and aluminian lepidomelanes, relation_________ 129,140 

Formulas, calculation of._____________________________ 115 

Foster, M. D. _........___..__._......____ 115,117,129,130,131

Qinzburg, A. I. and Berkhin, S. I-...._..._._.....___............ 117,128

Hallimond, A. F______________________________ 127,136,139 

Hendricks, S. B. and Jefferson, M. E.._______.__.. 117,124,125,127,139,140 

Heptaphyllitic micas.._____.___._____..____...... 119,127,129,135

Hey, M. H........._____._....._..__.........._____. 128,129,135,136

Interlayer cations_________________________________ 116

Jefferson, M.E. See Hendricks, S. B., and Jefferson, M. E.

Kunitz, Wilhelm____________________._________ 127,135,136

Le (2 Li, Si)................................................................ 127,128

Lepidolite series._________________________________ 126 

structure..._________________________________ 117,124 

Lepidolites, interpretation of composition..._______________ 116,126,166 

Lepidolite-muscovite association.________________________ 117 

Lepidolite-protolithionite series-_________________________ 127,128 

Lepidomelanes_________________________________ 115,135 

Levinson, A.A ___________._....___.___.. 117,124,125,127,140 

Lithian muscovites....____....__________________ 116,124,125,126 

interpretation of composition. _______________________ 125,126 

Lithian siderophyllites______________._______.____... 135,140

Page

Lithium and occupied octahedral sites relation- . . 122 

and octahedral Al, relation between....._.______.. 119,138

Li and Si relation...____.___________________ ... 131 

Li and total Al relation.____ . . ....__ 121

Lithium and trivalent octahedral cations, relation..__.__ 130 

Li, effect on formula calculation- .. 116 

Lithium micas. ______.. . 116 

Lithium micas, unusual- ____ 139 

Lithium muscovite____._ 116,119 

Li-(octahedral Al) replacement ratio._.__.__ 117,120,121,122,125,137,138,140 

Lithinm, relation to other constituents in calculated formulas.. 119 

Li and Fe« relation___...... .. . . .-.__............ ...... 130

Li -R« and Si relation......._............... .._._. . ........ 121

Li20 and F relation..____... ... _ _.__ 122 

Li20 content, octahedral occupancy, and structure....... 122

Magnesium-replacement system . .. 115,129 

Marshall, C. E.. .......... . . ................. 115

Miser, H. D__....________._...........__ ................. .... 139

Mixed structure..________. .. _ 124,126 

Muscovite.-..................... .... 116,117,119,123,124,125,126,127,138,139,140

Muscovite structure.______ . . 118,124

Octahedral group_........__ . 115

Octahedral replacement of bivalent by trivalent cations..-.. 115 

Octahedral replacement of trivalent by bivalent cations . 115 

Octaphyllic micas..... .- __._......._____ 119,127,129,135

Paucilithionite.-. . . . . 116,119

Phengite.____....._.__.__...._- ________ 128

Phlogopite...................... . . 115,139

Phlogopite-taenioli te series. . 139 

Polylithionite_............_. .. 116,119,120,126,127,132,138,139,140

Protolithionite . .- 116,127,129,132,135,138,139,140

, E.B. 136

Schaller, W. T................... ...... ....... .. 124

Siderophyllite. ..... ... .... ._-_ . 129,130,131,132,133,134,137,138,139,140

Siderophyllite-lepidolite isomorphous series___________ ... 132 

Siderophyllites and lepidomelanes___.____________ . .._ 115,134 

Stevens, E. E.. .... _ . 116,117,118,124,127,139

Structure of aluminum lithium micas-. .____.__.__ 124 

polymorphic variations in.. 125 

transition in__________ ...._.. . 124

Taeniolite.. __.._........ ..._....._. ....__ ...__ 116,139

Tetrahedral group________._._____________ 116 

Transitional samples.-..____ . ... 124 

Trilithionite._...............__...._.......__....... __ 119,120,124,127

Trioctahedral micas...__.__ . . . 115,119 

TrisUicic-tetrasilicic series _____ .... _____.__ .. 115 

Trivalent octahedral cations.__._____ ._____..__ . 130,131,132

Winchell, A. N......................................... 116,117,124,127,129,135,136

Zinnwaldite. _........._ 127,129,132,135,136,139,140

147

o