THE AMERICAN
MINERALOGIST,
VOL.49, JULY_AUGUST, 1964
CUMMINGTONITE-GRUNERITE
SERIES: A CHEMICAL,
OPTICAL AND X-RAY STUDY
Conr.rBrrsKr.etN, Jx., Departmentof GeologicalSciences,
H arpard IJniaer si.ty.r
AestnA.cr
Nine new chemical analyses of members of the cummingtonite-grunerite series are
presented. The material is from the high grade metamorphic, Precambrian, Wabush Iron
Formation, Labrador, Canada. These analyses and additional analyses from the literature
are recalculated in terms of the components MgTSi8Ozg(OH)2,FezSisOzz(OH)rand
MnzSisOz(OH)2 The solid solution within this ternary system is found to contain 35 to 100
mole per cent FezSisOzz(OH)r and 0 to 34 mole per cent MnzSisO:z(OH)2. Variation in
optical properties, unit cell dimensions and density within this solid solution series is
presented graphically in binary and ternary variation diagrams. Completely indexed
powder diffraction patterns are given for three chemically dissimilar members of the
cummingtonite-gruneril e series.
The 7 index and.Z/1e angle are the most easily obtainable optical parameters for determination of chemical compositions in the ternary system. The 6 cell dimension shows
an appreciable and systematic variation with composition, whereas a sin p and c vary
little. Manganoan cummingtonites (those containing 10 mole per cent or more
MnzSisOz(OH):) have physical properties which are so similar to those of the tremoliteactinolite series that the presence of manganese must be established chemically.
h.trnooucrror.t
The variation in optical properties as a function of chemical composition in the cummingtonite-gruneriteserieshas been published by Sundius (1924,1931)and Winchell (1938).Winchell'sdata refer to essentially
iron-magnesianmembers of the grunerite series,whereasSundius' work
includesgruneritescontaining up to 10.95weight per cent MnO. Bowen
and Schairer(1935) show the variation of optical parameterswith composition in synthetic fluorine analoguesof the iron-magnesian members
of the grunerite series.Jaffe et al. (1961) give chemical, optical and tr-ray
data for one manganoancummingtonite,containing 19.2weight per cent
MnO.
The present study was undertaken to investigate the variations in
optical and r-ray parameterswith changesin the Mg, Fe and Mn content
of the cummingtonite-gruneriteseries.
NounNcr.q.runr
The nomenclature of the iron-magnesian cummingtonite-grunerite
seriesused in this paper is similar to that suggestedby Jaffe et al. (1961).
Grunerite refers to (Fe, Mg)7Si30zr(OH)rwith Fe>Mg; cummingtonite
refers to (Mg, Fe)7Si3Ozz(OH)r
with Mg)Fe. The break between cum1 Mineralogical contribution no. 411, Harvard University.
963
9&
CORNELIS KLDIN
mingtonite and gruneritethus occursat 50 mole per cent Mgzsi8022(OH)
2.
The prefix manganoanis used wheneverthe "Mn" componentis present
in amounts larger than 10 mole per cent. The prefixes ferroan and
magnesiancan be used wheneverthe amount of the t'Fe" or "Mg" component exceeds10 mole per cent. The MnzSisOzz(OH)z
end-memberhas
not beensynthesized.is unknown in nature and is not named.The above
classificationis illustrated on a ternary diagram in Fig. 1.
It is suggestedthat the namescummingtoniteand gruneritebe usedfor
all members of the seriesinstead of varietal names such as dannemorite
(Erdmann, 1851) and tirodite (Dunn and Roy, 1938; Bilgrami, 1955;
fl.;sto?,(oH),
usrslo
Frc.
1. Suggested
?bti,
nomenclature
F#isorr(oH!
for the cummingtonite-grunerite
series
Segeler,1961). Chemical suffixesas proposedby Schaller (1930) can be
usedto indicate any variation in composition,if known.
DBscnrprrox oF SPECTMENS
The six grunerites and three manganoan cummingtonites used in this
study were collected by the writer during the summer field seasonsof
1959and 1961.All nine samplescamefrom the Wabush Iron Formation,
a high grade metamorphic Precambrian formation, which crops out in
the Labrador City area,Labrador, Newfoundland,Canada (Klein, 1960).
The grunerite samplesare part of the "silicate" and "silicate-carbonate"
horizons. The manganoan cummingtonites are found in the "oxide"
horizons. AII samples are coarse grained and completely free of altera'Ihe
tion.
mineral assemblageand mode, as estimatedin the hand specimen, are given in Table 1. A detailed study of the phase assemblagesin
theseiron formations will be published later.
965
CUM M I NGTONI T E-GRUN ERIT E SERI ES
Salrprn PnBp,tr,lrroN
AND Puntrrcattotq
All sampleswere ground to between minus 50 and 100 mesh. Samples
containing magnetite were then purified with a hand magnet (samples
No. 11A, 7 and 4). SamplesNo. 3 and 4, showing a black MnO2 stain,
were soakedfor one hour in HCI (1: 1) to dissolvethe MnOz. All other
sampleswere also soakedin HCI to remove any limonite coating. In all
casesthe Frantz Isodynamic separator was used to obtain a 90 to 95
per cent pure amphibole separation. Subsequentpurification was obTarr,n 1. MrNnnal Assrlrsr,ecns aNl Es:tru,ltro Moors lon NrNn Saupr,ns
Srnrrs
CoNr.qrNrNc Mnnnnns ol rnr CurrauructoNttr-Gnunnntrn
Amphibole
No.
1
9A
Assemblage
grunerite (60%) quartz (40l6)schist
grunerite (4016)-hypersthene-EnzFse
^rl^ft?
11A
7
8
10A
2
3
4
(30%)-siderite
(25o/)-
I \u/^ldnprcc
grunerite (50%)-actinolite (30/6)-diopside (1501) magnetite
(5 /6) -carbonate gneiss
(20o/)-magnetite
(l5ak)-calcite
schist
grunerite (60o/)-quartz
grunerite (900/6) quartz (lof)schist (asbestoform variety of grunerite)
(251) -carbonate gneiss
cluartz (.40o/) -diopside (30/6)-grunerite
Mn-cummingtonite (90/o) specularite (61) -quartz (2/6) gneiss
Mn-cummingtonite (80%)-specularite (2016)-schist (MnO, stained)
(307d -Specularite (10/6) schist
Mn-cummingtonite (60/6)-quartz
(MnOz stained)
tained with heavy Jiquidsusing methylene iodide and acetonemixtures.
The final purification of the samples was done by hand-picking under a
binocular microscope.AII analyzedsampleswere estimatedto be 99.8 to
100 per cent pure. Optical, tr-ray and density measurementswere made
on a separatepart of the analyzedsample.
Cnplrrcer, ColrposrrroN
Complete chemical analysesfor nine amphiboles are given in Table 2.
The number of cations calculated on the basis of 21 (O, OH, F) is also
g i v e n .I n c a l c u l a t i n gt h e n u m b e r o f c a t i o n st h e H z O ( - ) v a l u e sw e r e i g nored as these most probably representadsorbed,non-structural water.
Justification for this assumption is provided by the calculated values for
(OH, F) which are larger than 2 in six out of nine samples.Table 2 also
orovidescalculatedmolecularratios for MsO: FeO: MnO.
966
CORNELIS KLEIN
Upon inspectionof the analysesit becomesobviousthat Fe2+,M92+and
Mn2+ ions are present in very large amounts as compared to Ca2+,Na2+
and K+ ions. As such the X and Y (Mo, Mr, Mr, M3) positionsin the general formula X2Yb(Z8Orr)(OH)2
are almost solely occupiedby Fe, Mg or
Tasrn 2 Gnumtnrtn aNo CuuurNcroNtrn AN.q,lysrs
(ANarvsr JuN lro, Dnpr. ol Gnorocrca.r, Scrrxcrs, Hanvano Uxrvensnv)
SiOz
TiOz
AlzOs
FezOr
FeO
MnO
Meo
CaO
Na0
KrO
H,O.rHzOFz
PzOo
Total
Fz:O
Total
Spectrographically detected
elements
4 9. 0 1
0.05
0.00
49 33
o02
0.39
J
J1.56
000
010
51.95
o.o2
0.15
J
44 99
0.37
40 94
054
6.65
0.18
o12
o20
154
031
0.04
0.00
r28
031
1.00
01
100.63
o.42
too 21,
Cu, Ag
51 79
0.02
033
_1
I
34 40
070
l0 33
097
0.o2
005
1.99
33 70
0q9
10.44
010
008
0.05
254
o22
52.28
000
007
_1
34 38
o.23
10 72
014
0.09
018
1.97
0 .3 5
5 5 .7 4
0.00
o23
0.00
034
I
31 90
0 .5 7
t2 s5
079
0.r2
008
1.62
I
452
16.62
19 18
119
o.26
000
2.16
0.30
0.40
009
100.33
100.24
or7
100 16
Cu, Ag
Cu, Cr
Ag, Be
Cu, Ag
B
Cu, Co
Y, Yb
Cu, Co
Ag, cr
Y, Yb
Cu, Pb
55 10
0.00
0.10
_t
709
14.73
18 55
104
008
o02
2.26
0.43
028
11 08
13,17
17 00
122
0.13
002
205
0.43
0.23
100.45
0 .1 1
r00.34
Cu, Co
Mo, Ag
100 53
0.10
100.43
Co, Mo
Ag
Co, Cr
Mo
1\l
Numbers of ions on the basis of 24(O,OH,F)
Si
AI
AI
Ti
Fe
rvln
Mg
Ca
Na
K
OH
F
e7l
l:33)'Z!,,1:,T),
031
otl
8
-l
6 .1 4 J
+ .301
0 1 3|
^^l
2 J6f
0.
0 02)
9
9ll'0,
u. t t
I
orl
).06)
i i")'*
1.64
2 59
41
;.'t
n6(
701
021
02l
04)
02
;:)'*
8, 0 1
021
-l
001
:#l
oTltt 2
'
4 . I 1f 6 . 8 8
821
1rl
0
0*l 0 . 0 3 ) o . o 2 )
*l
02)
2
2.16\) te
-"
o.r2)-
1:,j,
"
Molecular ratio FeO :MgO:MnO
FeO
Mgo
MnO
88 17
11..12
0.70
76 8l
22 t2
108
64 26
34.38
1.34
63 22
34 90
189
64 02
3 5 .5 8
0.40
58 56
40 40
1 0.5
61 55
30 31
t In all analysesiron was determined in two ways: as total Fe and as FeO. FezOswas calculated by subtraction, In every analysis the so obtained value lor FerOs was 0 0/e uith a range oI error of 0 1/o (absolute)
As the absenceof FezOr was not proven by direct method, - is used instead of nil (Dr. Jun lto)
CUMMINGTONITE-GRUNERITESERIES
967
Mn. In addition, it should be noted that AlzOsis present only in very
small amounts, the maximum AIzOecontent being 0'39 weight per cent in
grunerite No. 94. The Z-position in X2Y1(28O22)(OH)zis thus almost
solely filled by Si. TiOz and PsOsare presentin trace amounts or are not
determinable. A few analysesshow an appreciable F2 content, the maximum being 1.00weight per cent in gruneriteNo. 1.
BecauseMgO, FeO and MnO are presentin large and variable amounts
and becauseall other oxide componentsare presentin very small amounts
only, the nine chemical analysescan be representedgraphically in terms
and MnzSigOz,
FezSiaOzz(OH)z
of three end-membersMgzSiaOzz(OH)2,
samplesNo.
that
diagram
from
this
(OH)r, as in Fig. 2. It becomesclear
in
a
two-component
phases
as
1, 9A, 11A, 7, 8 and 10A can be considered
"Mg-Fe" system. SamplesNo. 2, 3 and 4, however, can only be consideredin terms of three components"Mg-Fe-Mn." The completenessof
representation of the total analysis of these amphiboles in terms of the
"Fe-Mg-Mn" componentscan be expressedquantitatively by the ratio
ry:l
{4+
totdEtio*
Mn'?+(in XY Pos'figl') ,. 'nn
'uu'
in XY positions
Valuesfor this expressionare tabulated in Fig. 2.
analysesvaries from 0'10
The CaO content of the six manganese-poor
rveightper cent (0.02 Ca ions/half unit cell;sample No. 7) to 0.97 weight
per cent (0.16 Ca ions/half unit ceil; sample No. 11A). The grunerite of
sample No. 11A coexistswith actinolite (seeTable 1). From this assemblageand from its occurrencein a high temperaturemetamorphicdeposit
one may concludethat a content of 0.16 Ca ions per half unit cell is close
to the upper limit of calcium solubiiity in manganese-poorcummingtonite
and grunerite. Green (1960) gives complete chemical analysesfor a hornblende-cummingtonite assemblagebelonging to the sillimanite zone. This
cummingtonite contains 0.19 Ca ions per half unit cell, which is verv
similar to the value given earlier. These data lead one to conclude that
cummingtonitesand
the upper limit of CaO solubility in manganese-poor
gruneritesis approximately 1.5 weight per cent; they also make higher
CaO values recordedin the literature somewhatsuspect.In this respect,
it should be noted that the chemical analysis results presented in this
study do not support Layton and Phillips' (1960) suggestionthat Ca is
essentialto stabilize the lattice of cummingtonite.
The manganoanmembersof the seriesshow a range from 1.04 weight
per cent CaO (0.16 Ca ions/half unit cell; sample No.3) to l'22 weight
per cent CaO (0.19Ca ions/half unit cell;sampleNo. 4). Thesevaluesindicate that Ca is somewhat more soluble in the manganoan than in the
membersof the cummingtonite-gruneriteseries.
manganese-poor
968
CORNELIS KLEIN
Eight cummingtonite-gruneriteanalysesselectedfrom the literature
are also representedon Fig. 2. The analyseswere selectedon the basis of
high contents of MgO, FeO and MnO, as compared to Fe2O3,KzO, CaO
and NazO (maximum FezOecontent being 1.80 weight per cent in analysis U; maximum KzO content 0.11 weight per cent in analysis R; maximum CaO content 2.0 weight per cent in analysis U; maximum NarO content 0.29 weight per cent in analysis R). In addition, the analyses were
selectedon the basis of low AlzOa content, the maximum being 2.37
Values for
Fe2+ a Mtr+ *
Mnt* (in XY)
total cations in XY
No 1 -99 14 per cent
No 9A -98.49
No. 11A-97.73
No. 7 -99.42
No. 8 -98.72
No. 10A-97 36
No.2 -96.95
No. 3 -97 36
No.4 -96.82
-96.61
N
M
42.58
-97.06
R
-95. 10
D
-90.88
v
-97. 80
o
-95 .24
s
u
N
M
R
D
V
X 100:
(Nsuta)-Jafre et al. (1961)
(Mikonui River) Mason (1953)
(Rockport,Mass.)-Bowen and Schairer(193.5)
(Dannemora)
l
(V. Silvberg)
| Sundius(1924)
O (O. Silvergruvan)
S (Str<;mshult)-Sundius(1924)and
Palmgren (1916)
U (Uttersvik)-Sundius (1931)
Mn;storr(oHL
-9r.97
mersior,(onl
Fe;sLorrPHl
Frc. 2. Chemical composition of cummingtonites and grunerites. Numbered compositions refer to analyses in this study: Lettered compositions refer to analyses from the literature. The extent of the anthophvllite field is after Rabbitt (1948).
CUMMINGTONITE-GRUNERITESERIES
969
weight per cent in analysis M. This selection was necessaryin order to
permit graphical representation of the total analysis in terms of the components of the diagrams.
Figure 2 showsthat the naturally occurring members of this seriesvary
comfrom 35 mole per cent to 100 mole per cent of the FezSisOzr(OH)z
ponent and from 0 to 34 mole per cent of the Mn?Si80"(OH), component.
These limits of solid solution within this amphibole series can probably
be related to the crystal structure. In the general amphibole formula
position is invariably occupied by the
X2Y7Z8O22(OH)zthe X(Mt
Iarger cations whereasthe smaller cations fill the various Y (Mr, Mr, Mr)
positions. In the actinolite seriesCa2+always occupiesthe X position. In
members of the manganese-poorcummingtonite-grunerite series Fe2+is
the principal occupant of the X position, whereasthe remaining Fe2+and
Mg are distributed over the Y positions (Ghose, 1962).Inanalogy to this,
Mn2+ will probably occupy the X position preferentially in the manganoan cummingtonites. If Mn2+ were to occupy the X position only, and
were not to enter into the Y positions, only two out of seven cations per
half unit-cell would be filled by Mn2+. This "2f 7" boundarv is drawn in
on Fig. 2. Mn-cummingtonite No. 2 contains 2.O2Mn2+ ions per half unitcell, whereasJaffe's analysis N contains 2.28 Mr'2+ per half unit-cell. The
latter analysis sample was not completely pure however, and corrections
were made to subtract a certain amount of included spessartite.It is possible that not all spessartitewas actually subtracted from the analysis.
Jaffe's cummingtonite was associated with rhodochrosite, spressartite,
rhodonite, talc and qvartz, which reflects a very Mn-rich environment.
However, although the Mn-content of the environment was very high,
the number of Mn2+ ions per half unit-cell in the amphibole is still only
about 2. From this one may conclude that the "2f 7" line on the diagram
may well represent the maximum amount of Mn2+ that can be housed in
the cummingtonite or grunerite structure. This conclusionis in agreement
with the non-existenceof naturally occurring manganoan cummingtonites
and gruneriteswhich contain more than 35 mole per cent MnO;it alsoaccounts for the impossibility of synthesizing this material in the laboratory.
Figure 2 shows one other line drawn at "2f 7" in the anthophyllite
corner. AII amphiboles which have more than five out of seven cation
positions occupied by Mg are known to occur as anthophyllites. Those
with less than five out of seven cation positions occupied by Mg occur as
members of the cummingtonite-grunerite series. This probably implies
that the X position in monoclinic amphiboles is not suitable for housing
Mg. As such the "2f 7" Iine represents the maximum content of Mg in
the cummingtonite-grunerite series.
970
CORNELIS KLEIN
Oprrcer Pnopnnrros
The manganese-poormembers of the cummingtonite-gruneriteseries
( N o . 1 , 9 A , 1 1 A , 7 , 8 a n d 1 0 A ) a r e b e i g ei n c o l o r ,s h o w i n gv e r y s l i g h t t o
no pleochroismunder the microscope.The manganese-rich
members(No.
2, 3 and 4) are light green in color, and show no pleochroism.AII nine
sampiescommonly show multiple twinning parallel to (100). In the hand
specimenas well as under the microscopemanganoancummingtonitesare
easily confusedwith membersof the tremolite-actinoliteseries;members
of both seriesare light green in color and have very similar optical properties.
TaBLE 3. Oprrcal PRopERTTEslNn Crne.vlcr ANcr-rs non Nrnr
Mrlrsons ol tnr Cuul.rNcroNrm-GnuNrnrrr
Senrns
Amphibole
No.
^l
zAl
2Vt calc.
2V., meas.
Cleavage
rro{rro
Varia
tron
t 719
1 . 7 0 8 | 69+
I 693
1 700
1 690
I O/.)
I 675
| 679
1 667
1.660
1 659
0 040
0 041
0 034
0 034
13 14'
1,6"
17"
16-17"
93" 52', 98' 06', 83" 36', 88" 02'
94'
96.
85"
88" 02',
82"
53" 54', . q 3 ' 5 3 ' 5 4 ' 1 5 '
54" 02'
54' 04',
1. 6 9 3
r 675
1 659
0 034
1 688
1 652
| 661
| 671
1 614
1 648
1 656
1 . 6 3 0 | 634
0 032
o o22 0 027
1 8 - 1 9 " 19-20"
20"
87" 20', 107'28', 92" 22',
1 665
1. 6 3 8
o 027
19'
89" O2',
54626',
54'38',
1 -05l
t
+
t
t
001
001
001
002
Indices of refraction and extinction angleswere determinedby means
of a spindlestage(Wilcox, 1959)with oils checkedat the time of measurement by a Leitz-Jelleyrefractometer,using a sodium light source. Axial
angleswere calculatedfrom the expression:
tan2 V7 :
1/d2 -
t/p'
7/9'-
l/t"
Several axial angles were also measured directly on a 4-axis universal
stage. A compiete listing of the optical properties is given in Table 3.
Figure 3 is a graphical representation of the variation in optical properties in the manganese-poor
grunerites. The slope and position of the
curve for the 7 index is very similar to curves published by Sundius
(1931), Winchell (1938) and Trriger (1956). The deviation of the curve
from the determined points is however less than in Sundius' and Winchell'sdiagrams.The position and slopeof the B and a curvesare a little
different from published data. This is due to the fact that the B and cv
vaiues in this study were measured directly, whereas many of the published values for B and a were calculated using two indices of refraction
CUM M I N GTONI TE-GRU N Ii,RI T ]]. SI'RT DS
looo
go"
goo
2oo
150
to:
*r4tsiorroxt,
mole7.
Frc. 3. Variation in optical properties as a function of chemical composition in grunerites. Values for R, on the extreme right refer to grunerite from Rockport, Mass (Bowen
and Schairer, 1935) which contains 3 02 mole Der cent MnC.
972
CORNDLIS KLEIN
m";si,l,,ont,
t,
it
ll
I''
\
I
Ir R
6
,IB
tl
Frc. 4. Relationship of a and 7 indices with variation in Mg, Fe and Mn content in the
cumingtonite-grunerite series. Crosses with index values refer to a indices from the literature.
and measured2V.Index curves based upon direct measurementas in
this study are consideredto be more accurate than curves based upon
calcuiations involving measured 2V. An accurate 2V measurement on a
universal stage can be obtained only with extremely well controlled instrumental conditions (Fairbairn and Podolsky, 1951).
Figure 4 is a graphicalrepresentationof the variation in 7 and o indices
on a ternary diagram. Optical parametersfor the cummingtonites and
grunerites selectedfrom the literature, and referredto earlier in Fig. 2,
r"r4srrlrrtoxt,
rtiersirOrr0Hl
FaisiprrPHt
Frc. 5. Relationship between -y andZ\e with variation in Mg, Fe and Mn content in
the cummingtonite-grunerite series. Crosses with index values refer to 7 indices from
the Iiterature.
CUMMINGTONITD.GRUNERITE
SERIES
973
have also been used in constructing Fig. 4. Figure 5 is a plot of the variation in y andZ/\c. This diagram enablesone to determinethe molecular
percentage of the three end members through measurement .of the two
most easily determinedoptical parameters.
Cr,rev-q.cB
Prismatic cleavage fragments used in single crystal r-ray measurements were mounted on an optical goniometer for orientation. The
110n 110 cleavageangle was measuredand is recordedin Table 3. It is
possibleto find some correlation between cleavageangle and variation in
chemical composition. The manganoan members consistently have a
larger 1107\110cleavageangle than the iron-magnesiangrunerites.
UNrr CBr.r.CoNsr.qNrs
AII nine amphiboles were studied by the rotation, Weissenberg,precessionand powder methods. Precessionphotographs along the 6-axis
yielded valuesfor B, o-sinB and c sin B. Weissenbergphotographsabout c
yielded values for b and o sin B. Thus obtained values for o and 6 were improved by using do.o.oand do.rr.oos measuredon powder photographs
(cameradiameter 114.59mm). The value for c could not be bettered in
this manner as no high angle 001 reflections could be identified on the
powder diagram. Using the directly measured value for B, values for a
and 6 from powder diagrams, and c values from rotation or precession
photographs the powder diffraction films were completely indexed using
an IBM 7090 computer program for calculation of all possible d-values.
With the aid of indexed single-crystal reflectionsand an estimate of their
relative intensities, it was possible to assign single indices to a large
number of the observed diffraction lines. Without relative intensity
measurementsof single-crystal reflections it would have been impossible
to assign single indices, especially to many of the high angle diffraction
lines. Approximately twenty to thirty singly indexed powder difiraction
lines with 20 above 30o were then used in a least square program for refinement of the unit cell parameters.The cell constantsfor cummingtonite
No. 2 were refined in this manner, using the least-squarerefinement program developedat the U. S. GeologicalSurvey. The unit cell parameters
of the other eight samples were refined on the Harvard IBM 7090 computer using the program developed by C. W. Burnham at the Geophysical Laboratory, Washington.
The final values for a,b, c, B, V(unit cell) and o sinB compatiblewith
the spacegroup C 2fm are given in Table 4. The accuracy of the values for
grunerite No. 7 is relatively low because of the inherently broad and
CORNELIS KLEIN
f.uzzy difrraction lines on its powder diagram. For this grunerite the accuracy rangesfrom 0.03 per cent in a, to 0.07 per cent in D and to 0.2 per
cent in c. The accuracy for the other eight amphibolesis considerably
better, ranging from 0.02per cent in o of No. 2, to 0.13 per cent in c of No.
4. A higher accuracy would have resulted if the experimental conditions
for obtaining the powder diffraction data had been more controlled (see
powder diffraction data).
Tllln
a,A
ta
ir
", deg
0,
V (A')
asing,A
4. UNrr Crr,r, DnrnwsroNs ron NrNr Mrunnns ol run CuulrrNGToNrrEGnuNnnrrr Sonrus (Srecn Gxove C2/m)
9.562+.0020
18.380+.0070
5 .338+ .0035
101.86
+.026
9182 +.7
9.359
No. 7
arA
b,A
crA
0, deg.
V(A)
osinB,A
9.545+.0038
1 8 .2 5 8+ . 0 1 3 7
5.320+0112
1 0 1 . 9 6+ . 0 8 6
9 0 7 . 1 1+ 1 . 4
9.338
9 . 5 5 1+ . 0 0 1 2
18.324+.0061
5 328+.0040
1 0 1 . 8 6+ 0 1 8
912.5 +.62
9.3+7
No. 8
9.527+ .0017
18.238+.0062
5.326+ 0046
1 0 1 . 9 5+ . 0 3 4
9 0 5 . 3 9+ . 6 4
9.320
No. 2
o, ft
o,A
ir
", deg.
9,
V (A')
a s i n B ,A
9.5831.0023
18.091+.0050
5.315+.0043
102.63+ .O23
8 9 9 . 1 3+ . 5 5
9.351
9 . 5 3 8+ . 0 0 1 8
18.248 + .0096
5 . 3 4 9 + .0059
r01 97 + . 0 2 6
9r0 74 + . 8 9
9.330
9 . 5 3 4+ . 0 0 1 9
r8-23r + 0017
5 .3235+ .0014
101.97 + 033
905.14 t .61
9 326
No.4
9.560+.0019
18.089+.0039
5.309+.0036
+.031
102.36
896.8 + .47
9. 3 3 8
9 . 5 7 3 + 0026
1 8 1 1 5 + .0054
5 304 + . 0 0 7 3
1 0 2. 3 5 + . 0 5 9
898.46 + . 8 2
9.352
Figure 6 is a plot of the variation of b, o sin B, and V as a function of
composition for the managanese-poormembers of the cummingtonitegrunerite series.From this figure it becomesclear that the D parameteris
most influenced by changesin composition.
Figure 7 is a ternary diagram showing isodimensionallines for b as a
function of Mn, Mg and Fe contents in the cummingtonite-grunerite
series.When more such data becomeavailable the attitude of the isodimensionallineswill becomebetter substantiated.
975
CAM M I N GTONI TE-GRU N ERI TE SERI ES
8.45
t8.40
70
., E0
mote /.
t8.t0
to
r"*'r,
o etr2
7
822
Frc. 6. Variation of 6, V, and a sin p(drno) as a function of the
chemical composition of grunerites.
976
CORNELIS KLEIN
Poworn
Drrnn,lcrror.t
P,\rrBnNS
Powder diffraction patterns for all nine amphibolesof this study were
obtained with a cameraof 114.59mm diameter, using filtered iron radia t i o n ( M n f i l r e r ; F e k a : 1 . 9 3 7 2 8 A ; F e k a 1 : 1 . 9 3 5 9 7 0A ) . n t t f i l m s w e r e
exposedfor 48 hours in order to obtain relatively intense back reflections.
During the exposure the temperature was not controlled. An internal
standard was not mixed with the amphibole samplesas it was found that
some difiraction lines in the crowded amphibole pattern were being
masked by the use of a slandard. The spindles,rolled with collodion, were
dilute and approximately 0.1 mm or less in diameter in order to reduce
^ n;s,rtrrOrt,
Msrslorr(oHl
Fe;'sisorJoHl,
Frc. 7. Diagram showing isodimensional lines for b (attitudes somewhat tentative) as
a function of chemical composition in the cummingtonite-grunerite series.
absorption effectsin the low angle difiraction lines. The spindleswere very
accuratelycenteredin the cameraby meansof a lens.Tbe only correction
applied to the resultant powder films was a shrinkage factor. The films
were measuredwith a scalereading directly to 0.05 mm. It was not always possible to locate the diffraction lines to such accuracy, as many
high angle reflection lines were Iuzzy and not always 'rvellresolved in a1
and a2 doublets. The accuracy of the unit cell constants given in Table
4 is not only a function of the experimentalconditions but also of the
inherent broadnessand fuzzinessof many of the powder difiraction lines.
Table 5 gives completelyindexedpowder diffraction diagramsfor two
grunerites (No. 1 and 10A) and one manganoancummingtonite (No. 2) ;
measured and calculated d-values are given and compared. The estimated relative intensities of the diffraction lines are subject to error as
the most intenselines were highly overexposedin order to obtain better
definition for less intense high angle lines.
977
CUM M I NGTONI T E-GRUN ERIT E SERI ES
Tler-r 5. X-Rlv Pomnn Du'lnectroN Dlre lon Two Gnur.rrnrrts eNo ONr
M e N c e N o , q NC u u u r x c r o N r r e ( F e K a : 1 . 9 3 7 2 8 A : F e K a r : 1 . 9 3 5 9 7 0 A ; M r F r r r n n )
Grunerite No 1
Grunerite No, 1
I
50b
100bb
vf
30
30
35
40
50
vf
hkl
d(obs)
d(calc)
020
110
001
111
200
040
220
131
22L
9 208
8.330
5 197
4 840
4.677
+.582
4.160
3.880
3. 592
3.466
3 278
3.071
9. 190
8.339
5.224
4.844
4.679
tJt
2 40
foeo
50
80b
[3
40
90b
70
60
10
vf
40
151
061
202
261
350
Jo 8 o
\ssr
42L
3 t2
vf
40
50
lz o t
\t 2 4 ,
l0 8 1
\202
35
30
10bb
ISDD
vf
vf
vfb
db
20
vf
vf
10
J . l l
[reo
l'370
402
422
191
460
11 e 1
l.010 0
|
37
082
372
d (obs-calc)
_ .018
-.009
-.o27
-.004
- 002
_.013
- .009
-.004
- .004
4.169
3 884
3 596
- oo2
3 468
0
3 278
i.r . oo.r
/+.ooa
[3.07s
\- oo+
-.0050
2.9969
3 . 0 01 9
-.oo29
2.7684
- .0034
2.6391
2.6425
-.0040
2. 5070
2.5t10
2 4120
2.4t08
+ 0012
- .oo72
2.3713 2.3785
2.2995 (c tot<
f+.oozo
2 2480
2.2245
2.2019
2 1015
2.04+8
1.9960
[ - .00s8
- 0021
- .0014
-.oo29
Iz.zo+s[ - . c 0 1 6
l'2.203s I
l 2 . t o 3 r I .0016
l.2.1040 | - n n ? <
2 0471 - . o o 2 3
fr oo<r
1+.oooz
\2 oo88 l - o r ? 9
1.9538 +.oo22
1. 9 1 1 1 + 0004
1.8918 -.0013
1 8 5 9 3 - 0002
\2.30s3
2 2501
2.2259
1. 9 5 6 0
1. 9 1 1 5
1. 8 9 0 5
1.8591
1.8370 J
i
| 7966
t.7243
1 ?083
r.6J/J
1. 8 3 8 0
1 7969
| 7251
1 7052
-.ooo3
I[
.0010
- .0003
- 0008
+ 0031
10bb
30
20
| 6882
I 6851
I 6678
1 6664
1.6449
1. 6 4 4 0
1 6013
I 6015
(
r <c?o
I 5875
J I
46
I 11
I J
10
10b
20
l )
10
vI
(t
o
12 10
60
012
35
55
14 4
60
3 11
410
66
vtD
J)D
25
20
5
10
35bb
10
vf
vf
20
vI
vib
5
10
l.)
10
5
20
10
t.)
5
10
,]
J
-.0031
-.0014
- .0009
+.0002
I -.oooa
\ r . s o o s| - . 0 0 3 3
- -ool2
1 . 5 5 8 6 1. 5 5 9 8
1 . 5 3 1 4 1 . 5 3 1 6 - 0002
1 . 5 2 3 5 - .0005
1 5230
- 0001
1 5108
1 5109
1 5002 I r . +qq.r | +. oooq
[1 . s009 l. .0007
- . 0 01 8
1 4191
1 . 4 77 9
- 0009
1 4729
1.4720
1. 4 4 0 8
1 .4409
+ 0001
- 0015
1. 4 0 8 9
I . 4 0 74
1 . 3 8 8 4 I t . s a t o / +. ooos
t,,
vf
10
d (obs-calc)
d(obs)
hkt
I
I
\ 1.38e2 I - . o o o 8
1 11
113
66
2t2
412
40
64
31
79
412
5
l l
410
7tr
0
2
2
3
0
1
86
86
0
95
2
80
2
82
614 2
t Reflection 4 12 2 (d, obs.:1.1029) and higher are Kdr reflections
b:broad
bb:very broad
vf:very Iaint (I estimated :i5)
I 3705
1. 3 4 0 9
1 3326
1.3081
| 2796
1. 2 5 5 3
1.2390
I . 1907
t.1721
1.1235
1.1195
| 10291
1 0699
1 0489
t -o4+l
1 0309
1. 01 8 1
1 .0005
9940
.9888
.9821
1 3697
r.3402
r.3325
1.3076
1.281s
1 2555
| 2372
1.1902
r l7r2
1 1229
1.1185
1 1024
1 0695
1 0486
1. 0 4 3 9
1 0307
1 . 0 17 8
1 0006
9941,
.9883
.9821
+ .0008
+ 0007
+.0001
+.000s
- . 0 01 9
- 0002
+ 0018
+ 000s
+.0009
+ .0006
+ 0010
+ .0005
+.0004
- 0003
+ 0002
+.0002
+.0003
-.0001
- .0001
+.000s
0
978
CORNELIS KLEIN
Tmr-n 5-(continued)
Grunerite r\o, 10A
I
d(obs)
.50
100b
20
20
40
40
30
30
80
90
20
70
50
10
30
10
30
15
0
0
0
I
0
0
1
1
0
0
1
1
1
0
2
0
I J
50
It
20b
vf
vf
15
5
10b
vf
vf
vf
.50
40
15
l5
19
37
LO
9 115
8.302
5 085
4.827
4 549
4.139
3.869
3 446
3 258
3 . 0 6 31
2 . 9 8 73
2 . 75 3 8
2 6232
2 5040
2 36s9
2.2932
2 2+O8
2 2129
2.1904
2 0950
2 . O 3 75
I 9951
1 9756
I 9510
| 8171
1.8521
It o r
\oro o
d (calc)
9 115
8 303
5 091
4 832
4 558
4 151
3 866
3 .4.50
3.259
3 0645
2 .9882
2.7510
2 6245
2.5457
2.5058
2 3656
2 2947
2 2436
2 2122
2 1912
2.0958
2.0361
| 9964
I 9795
| .9532
I 8780
1.8s56
Grunerite No. 10A
+
+
-
0
001
006
005
009
012
003
004
001
. 0 01 4
.0009
.0028
.0013
- oo22
- 0018
- . 0 0 17
- 0015
- oo24
+007
- .0008
- 0008
+ 0014
-.0013
- .0038
- oo22
-
0009
0035
I t.tzso ([ - . o o : r
\ r a z : r l' - .0023
512
551
461
I 11 0
153
1 6839
1 . 6 72 9
I 6586
I 6.310
I 5951
l+ o z
\zro r
t - 5800
I 6845
| 6742
1 .6.s90
1 6318
1 5954
-
.0006
.0013
.0004
.0008
0003
hkl
I
d(obs-calc)
25
40
vf
vl
vf
15
vf
60
10
vf
20
40
30
0
60
ot2 0
55
1
48
I
2
60
311 0
410
66
J I
I 11
71
0
0
\z tz 2
412 0
li I 1
l2 12 2
412 1
64
2
lso 0
\z s 1
79
o
lo tz 1
\+ rz 2
0
86
5 11 2
93
I
711 0
1
86
a
86
+4
5
66
3
2
80
88
I
(
vf
30
IJ
vf
10
vf
TJ
vf
40
10
10
10
10
vf
vf
d(obs)
d(calc)
1.5541
1 5 1 8 2 1 5192
1 .5040
1 5037
1 4931
|.4947
64
| 4766
1.47
1 . 4 6 2 7 | 4625
1. 4 3 0 5
| 4322
1 4028
I 4033
1 3821
| 3822
1 3599
1 3606
1 3284
r .3288
1 2990 J r tot+
d (obs-calc)
- .0003
- 0010
+.0003
-.0016
+ 0002
+ .0002
- 0017
- 0005
-.0001
- 0007
- 0004
| - ooz+
\ 1 . 2 e e 1 I- oool
1 2730
| 2 7 2 9 + 0001
1 2287
! r .zzto I+- . 0ooot
014
ll .2301 I
1 2054
1 1851
+ .0003
- .0005
I t ttst /a ooos
\r reoz \ - ooor
1.1131
1.0887
1.0634
I 0439
1.0387
1 0263
t.0152
1.0083
- .0003
Jr oosa1+. oool
\ r . o o s oI + . 0 0 0 6
1.0884
1 0633
1 0436
1 0384
I 0263
I ot49
1. 0 0 8 7
+.0003
+ .0001
+.0003
+.0003
0
+ 0003
- 0004
- .00010
+ ooo24
- .00050
/ r .s s r s / - . o o r s
) r sros
I + ooos
2 Reflection7 9 0 (d obs.:1.1128) and higher are Kar reflections.
b:broad
bb:very broad
vI:very faint (I estimated :15)
Spncmrc Gnavnv
Specificgravity determinationswere made with the Berman Microbalance (Berman, 1937) using 20 to 25 mg samplesof minus 50 to 100
mesh grain size. Densities were calculated from the composition and
unit cell volumes.Table 6 gives the measuredand calculatedvalues.The
agreementbetween these is good except for samplesNo. 7 and No. 9A.
These two grunerites show a differenceof 1.7 per cent and 2 per cent,
respectively,betweenthe calculatedand measuredvalues.Deviations up
to severalper cent are not uncommon (Mason, 1944,p.50); considering
CUM M I NGTONI TE-GRUN ERI 7'Ii SERI ES
979
T xll-r. 5- (continu.ed,)
Manganoan
hkl
80b
90bb
vf
20b
20
50
40
vf
35
vf
60b
80b
100b
30
IJ
40
70
20
50
50
5
J L
31
61
o2
11
22
50
77
20
40
40
30
20
50
vf
20
30
20
30
t2
42
61
32
02
J I
70
o2
50
vf
10bb
10
40
30
60
40b
30
vf
10
20
10
01
30
11
40
20
11
31
2l
31
40
10
21
51
30
cummingtonite
No
2
d(obs)
d(calc)
9 034
8 296
5.179
5 040
4 834
4 516
4 150
4 054
3 856
3 602
3 426
3 251
3 071
2 968
2 932
2.766
2.726
2.661
2.6027
2 5111
2 4205
9 045
8 307
5.i86
5 068
4 842
4 523
4.153
4 059
3 861
3 601
3.472
3.251
3.O27
2.972
2 936
2.769
2 726
2.667
2.6066
2 5127
(1
411e
2 3 5 7 5 2 3615
2.2959
2.2983
2 2525
2 2570
2.2312 2.2328
2.1925
2 1965
2 . 1 74 2
2.1772
2.1044 2.1081
2 0199
2.0821
2 0255
2.0263
1 9850
1. 9 8 9 5
1 9606 ( t . s e z s
Manganoan
_
-
011
.011
.007
028
.008
007
.003
005
.005
+ 001
- .006
0
-
004
004
003
0
00s
0039
0016
! -.oots
i-.0006
- 0040
- 0024
- 0045
- 0016
- 0040
- 0030
- .0037
- .0028
- 0008
- 0045
! -.oozt
l '1. 9 s 9 s I + . 0 0 1 1
1. 8 6 0 0
1 8603 - 0003
- 0030
1 . 8 4 1 0 1 8440
1 8023 ( r r o o s I + . 0 0 2 8
\ 1. 8 0 e 1 | - . 0 0 6 8
1. 7863 - 0 0 1 5
(| 1 . 6 9 6 4 | - . o o r t
5l
| .6768
| 6494
1.6189
r 5877
1 5566
1 5311
1.5139
61
11 0
J I
00
20
70
40
30
30
10
75
30
10bb
20
vf
10
35
\- ooro
- 0030
- .0030
- 0008
- 0020
- 0019
- .0047
- -oo12
hkl
d(obs)
o12
1'"
|.60
3 11
410
66
J I
1 11
66
l13
012
(t rt
25
10
5
5
.)o
5
5
30
15
10
10b
15
75
412
40
60
IJ
l4
10
1l
0
4
i4
6
25
vf
vf
IJ
10
20
5
5
40
35
20
20b
20
vI
20
30b
vf
10
10
5
5
12
11
7
9l
7tl
Js s
\o rz
86
86
610
614
26
!z ro
\o o
71r
313
J ar o
14 6
6IL
3 Reflection 5 11 t (d obs. : 1.1828) and higher are Kdr reflections.
b:broad
bb :very broad
vf :very faint (I estimated 55)
No. 2
d(calc)
1 5076
- .0008
I t . + s t a ! +.oooz
\1.4szl\+.oor+
r 4541
| 4277
I 4063
1.3766
I .3495
1. 3 3 3 3
| 3t97
1. 3 0 3 0
t.2921
1.4546
1 4291
1. 4 0 7 5
1 3764
1. 3 5 0 9
1 3337
1.3199
1.3033
+ 000s
- 0014
- .0012
+ 0002
- .0014
- 0004
- .0002
- 0003
I t zoza J - oooz
\- ooor
) r rorr
\o r+
+ . 0 0t
81
10
61
t2
100
30
I2
72
| 1. 6 9 7 0
1 6798
1 6524
1.6197
1.5897
1 5585
1 5358
1. 5 1 5 1
I
d(obs calc)
cummingtonite
r.2789
r 267I
|.2570
| 2218
|.2097
| .1952
I 1881
1 18283
1. 1 6 8 9
1 .1 5 7 1
! 1298
1.1166
r.rr32
1.1030
I 0967
1 0888
1.0817
1.0576
1 0508
1 0451
1 0371
1 0309
1. 0 2 5 3
1. 0 2 0 6
I ot32
1 0030
1 . 0 01 8
.9910
.9860
.9829
9792
.9757
1 2795
1 2670
r 2564
| 2229
1 2095
1 1954
1. 1 8 7 3
1 .1 8 3 3
1 .1 6 8 9
t.1579
1 . 3 01 4
1.1164
t.1132
t.1029
1.0962
1. 0 8 8 6
1 0814
1.0573
1. 0 5 0 9
1 0450
1. 0 3 6 9
-.0006
+.0001
+.0006
- .0011
+ .0002
- .0002
+ 0008
- .0005
0
- 0008
- _0 0 1 6
+ 0002
0
+ 0001
+ 0005
+ .0oo2
+ 0003
+
+
I t osrt i \1.02e8 \1
1 0253
1 0206
1.0132
1. 0 0 3 2
1 0025
.0003
0001
0001
0002
ooo+
oorr
0
0
0
- 0002
- .0007
J ooio l o
\ ooos \a oooz
. 9 8 5 1 + 0009
9829
0
I ozoz / - ooos
\ oroo \ - oool
.9'r54 +.0003
980
CORNELIS KLEIN
Terr,n 6. Mrlsunm Spr'crnrcGn,lvrry lxo Clr,curernn Drnstrv V,qrurs
ron Nrrr MnMerns or rnn CulrurNcroNrro-GnuNemre Snntes
No. 1
meas.
calc.
No.94.
No 11A
No. 7
3 . 5 4 +. 0 2 3 . 4 5 + . 0 2 3 . 3 8+ . 0 2 3 . 4 1 +. 0 2
.t.J)
354
3.51
3. 3 8
No.
meas.
calc.
No
No. 3
3 . 1 3 + . 0 2 3 . 2 1 +. 0 2
3.18
3.19
3 . 2 2 +. 0 2
3.24
the many possible and difficult to evaluate sourcesof error in the calculated density values the correspondenceis still satisfactory. Figure 8 is a
plot of the variation in specificgravity as a function of chemical composigrunerites.
tion in the manganese-poor
DrscussroN oF RESULTS
The chemical analysesfrom the literature and the new analysesin this
study show clearly that the cummingtonite-grunerite seriesshould be con3.80
sp.gr
9A
g-colculoted
. - meosured
'?";rio,Jort
Frc. 8. Variation in specific gravity (measured and calculated) as a function of chemical
composition of grunerites. Value for R refers to grunerite from Rockport, Mass. (Bowen
and Schairer, 1935).
CUMMINGTONITE-GRUNERITESERIES
981
sideredin terms of at least three components"Mg-Fe-Mn." The AlzOa
component is generally small, ranging from zero to about three weight
per cent, but may at times be presentin amounts up to 8.65 weight per
cent (Collins, 1942). The CaO content varies from trace amounts to a
probable maximum of approximately 1.5 weight per cent. The effect of
the presenceof AlzOa,CaO and minor amounts of FezOs,KzO and NazO
has not been consideredin this work.
The variation in optical parameters, unit-cell constants and specific
gravity as a function of chemical composition in the "Mg-Fe-Mn" cummingtonite-gruneriteserieshas beendetermined.It shouldbe noted, however, that manganoan cummingtonite is still not readily identified as
such by its phvsical properties. The manganoan cummingtonites of this
study are light green, show no pleochroism and have optical properties,
f-ray parameters and densities which are ver)r similar to those of the
tremolite-actinolite series. This means that the presenceof manganese
must be establishedchemicallv.
AcrNowr-BoGMENTS
I wish to acknowledgethe Iron Ore Company of Canada for enabling
me to study the Laborador City area and to collect samples during the
1959and 1961summer field seasons.The Iron Ore Company of Canada
also provided funds for the chemical analyses.I am indebted to Professor
G. Perrault, Ecole Polytechnique, Montreal, Canada for his enthusiastic
guidance during the early part of this investigation. Thanks are due to
Dr. Malcolm Ross of the U. S. Geological Survey for his interest in and
advice on several r-ray crystallographic problems. Dr. David B. Stewart
also of the U. S. GeologicalSurvey is gratefully acknowledgedfor refining
the unit cell parameters of one amphibole using his refinement program.
I wish to thank Dr. C. W. Burnham, of the GeophysicalLaboratory,
Washington for making his computer program for refinement of unit cell
parameters available to me, through Mr. D. R. Waldbaum, graduate
student in GeologicalSciencesat Harvard. The help of Ruth Lewin, Department of Chemistry, Ilarvard University, in writing a computer program for the Harvard IBM 7090 for calculation of d-spacingsis acknowledged. I am grateful to ProfessorsClifiord Frondel, J. B. Thompson, Jr.
and C. S. Hurlbut, Jr. for their counseland critical reading of the manuscript.
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Manuscript receiled.,Decentber3, 1963; oeceptedJor publication, January 31, 1961.