THE AMERICAN
MINERALOGIST,
VOL. 47, JANUARY-FEBRUARY,
1962
STUDIES OF THE MANGANESE OXIDES. V. RAMSDELLITE, MnO2, AN ORTHORHOMBIC DIMORPH OF
PYROLUSITEl
Mrcnapl
FlBrscnpn.2 W. E. RrcuMoND.s AND
Howano T. EvnNs, Jn.2
ABSTRACT
Ramsdellite is an orthorhombic dimorph of pyrolusite; the composition is close to
Mnoz with no certain deviation from that composition. rt inverts to pyrolusite at about
300'; the inversion is presumed to be monotropic. Examination of crystals from the
Gavilan Mine, Mexico, shows them to be pseudomorphs after groutite; a secondary lattice
is probably that of an intermediate stage of oxidation. chemical analyses and *-ray data
are given, and the physical properties are summarized.
fNrnooucrroN
Early in 1941, in the course of an extensive study of manganeseoxide
minerals, a sample collected by S. C. Creaseyof the U. S. Geological
Survey from Lake Valley, New Mexico, was found to give a distinctive
fi.-ray pattern. Analysis showed that the composition was close to MnO2;
at our requestMr. Creaseycollecteda largesuite of samples.Through the
courtesy of ProfessorL. S. Ramsdell of the University of Michigan, we
obtained his specimen,from an unknown locality, of a dimorphous form
of MnOz (Ramsdell, 1932); it proved to be the same mineral as that from
Lake Valley. It was named ramsdellite and a preliminary report, in which
this name was used, was published in 1943 (Fleischer and Richmond,
1943).At that time, chemicalanalyseshad been made, the inversion to
pyrolusite had been noted, and a preliminary determination of the unit
cell had been completed.
Shortly thereafter,Dr. Richmond left the U. S. GeologicalSurvey, and
Fleischerwas assignedto more urgent work for the Manhattan Project;
various circumstances have unfortunately prevented the publication of
the data on which the new mineral name was based.We have, however,
supplied many investigators the world over with samples from Lake
Valley, and some twenty papers dealing with the mineral have appeared;
all the data on Lake Valley samples cited were obtained on samples supplied by the U. S. GeologicalSurvey. This paper gives our data and summarizes the published information.
Cunurstny
All available chemical analysesof ramsdellite are assembledin Table 1.
The compositionis closeto MnO2, but the ratio of total cations to oxygen
1 Publication authorized by the Director,
U. S. Geological Survey.
2 U.S. Geological Survey, Washington, D. C.
3 R.F.D. No. 2, Hillsboro, N. H.
47
48
M. FLEISCHER,W. E. RICHMOND AND H. T. EVANS, JR.
Talle
MnOz
MnO
Mso
ZnO
BaO
CaO
NarO
KzO
H:OH:O+
AhOr
FezOe
SiOz
TiOz
PsOu
Active O'
Total Mn
ActiveO/Mn
G.
97.14"
none
012
n.d.b
none
none
0.31
0.41
(
I
1 r. z +
I
I
1, Cnnurc,lr, Axer-vsns ol Reusoelltrr
95.O2"
none
none
0 .250
none
l.r2
0.05
r.39
0.72
0.22
0.36
none
n.d.
100 46
99.r3
17.49
59.62
1 .007
4.65
0.68
0.28
tt'
tt-
0.2
present, n.d.
present, n.d.
0.48
0.34
0.42
none
none
17.88
61.00
1.006
4.73
0.96
0 .1 6
I1 . s
J
l.
0.8
1.2
0.8
0.2
(
\o.oz
I
(
I
i0.96
t
Y
61.28
t'r
60.17
4.83
* calculated from active o; determination by the method of Fleischer (1943). Active
O:oxygen reactive with oxalic acid, that is, oxygen above the requirements for MnO'
b Shown by K.
No. 2.
J. Murata spectrographically to contain about as much Zn as
of the same sample'
" Determined by C. M. Warshaw on a separate portion
1. From Lake Valley, New Mexico, analysis by Michael Fleischer in 1942; X-ray study
showed that the sample contained considerable pyrolusite.
2. Locality unknown, Ramsdell's type specimen; analysis by Michael Fleischer in
1942; X-ray study showed a very small amount of pyrolusite'
3. From Lake Valley, Bystrdm (1949).
4-6. Three difierent samples from Lake Valley, analyses by Charlotte M. Warshaw in
1951; X-ray study showed very small amounts of pyrolusite.
is not known becauseof the uncertainty as to the role of zinc (present in
all the Lake Valley samples), calcium' alkalies, and H2O. The SiOz,
Fe2O3,and,AIzOspresent are assumedto be due to impurities (chert and
iron oxide are known to have been present).Spectrographicanalysesby
K. J. Murata showed that beryllium, cobalt, nickel, thallium, and
vanadium were absent in samples I and 2 of Table 1 and showed traces of
lead and 0.0X per centZn in ramsdellitefrom the Gavilan Mine, Lower
California, Mexico. A semiquantitative spectrographic analysis was
RAMSDELLITE, ORTHORHOMBICDIMORPH OF PYROLUSITE
49
made by Nancy M. Conklin in 1959of another sample from Lake Valley;
she found (weight per cent) Mg 3, Ca 0.15, Fe 0.C15,Zn 0.7, Ag 0.015,
C u 0 . 0 0 3 ,M o 0 . 0 3 , V 0 . 0 1 5 , W 0 . 0 0 3 , P b 0 . 3 , B a 0 . 0 7 ,S 0 . 0 0 7 , a n d
Y 0.003.
As discussedlater in this paper, ramsdellite is related structurally to
gamma-MnO2 (or Nsuta MnO2, Sorem and Cameron, 1960), which is
generally believed to be a defect structure with Mn:O less than 2.
Wadsley and Walkley (1951) state, "A specimen (of ramsdellite from
Lake Valley) has been analyzed by the authors, and in common with all
the manganesedioxides shows a departure from true stoichiometric proportions. The cell dimensions and the thermodynamic properties should
therefore be capable of some variation." The analysis unfortunately is
lost (A. D. Wadsley,priv. comm. to Fleischer,1960).The published*-ray
data on ramsdellite(Table 3) show no indication of compositionalvariation.
Bpuevron WuBN Hnaroo
Ramsdell (1932)reported, "After heating to a low dull red heat, a normal pyrolusite pattern was secured. This heating was accompanied by a
Iossof water of only 1 per cent and the total loss in weight was less than 2
per cent. This would seem to eliminate either dehydration or a change
from some other oxide as a causeof the change in pattern. A possible explanation is that this specimenrepresentsan unstable form of MnO2,
which is convertedto the normal form by heating."
We confirmed Ramsdell's observations in studies of Lake Valley material. Samples heated in air at 200orfor 4 days and at 240" for 7 days
showedno changein *-ray pattern, but a sampleheatedat 310ofor 5 days
had been converted almost entirely to pyrolusite (r-ray data by J. M.
Axelrod). Klingsberg and Roy (1959) found that ramsdellitefrom Chisholm, Minnesota, was unchangedwhen heated in air at 316ofor 4 days,
but gave a trace of pyrolusite when heated at 313" for 14 days. They also
reported that groutite, MnO(OH), changedslowly to ramsdellite above
130", changedin a few hours at 300", but above 300oit went directly to
pyrolusite.
Difierential thermal analysis curves for ramsdellite have been pubIishedby McMurdie and Golovato (19a8) (Lake Valley), Kulp and Perfetti (1950) (Idorado Mine, Colorado),and by Caillbreand Kraut (1954)
(locality not stated). Kulp and Perfetti found a small endothermic peak
at l2Do (capillary water) and an exothermic break at 500ocorresponding
to the inversion to pyrolusite. Cailldre and Kraut found a break at 450o.
McMurdie and Golovato report that "below the first break at 670oheat
t This and all other temperatures are "C.
50
M. FLEISCHER,W. E. RICHMONDAND H. T, EVANS,JR.
was being absorbed and r-rays indicated a change to pyrolusite. This
changefrom ramsdellite to pyrolusite does not appear to occur sharply or
to be accompaniedby a large energy effect,and is not reversible."After
the inversion to pyrolusite, the D.T.A. curves,as might be expected,are
essentially identical with those given by pyrolusite, except that Caillbre
and Kraut report an extra endothermalbreak at 850o.
The inversion of ramsdellite to pyrolusite is presumably irreversible
and monotropic, although there is no direct evidenceof this;very likely
the inversion would occur at temperatures below 300' if sufficient time
were allowed.It should be noted that neither ramsdellitenor groutite has
ever been synthesized(Moore, Ellis, and Selwood,1950) although they
are readily converted into one another hydrothermally (Klingsberg and
Roy, 1959).
Cnvsrar,r,ocRAPurcAND X-RAY Sruorns
The first work on the crystal structure of ramsdellite was by Richmond (quoted by Fleischer, t944), who determined the orthorhombic
symmetry and the approximate cell constants on cleavagefragments from
Lake Valley, and who recognized the similarity to diaspore. The structure was worked out by Bystr<im (1949) on Lake Valley material. She
with the cell constants
found it to be orthorhombic, space group D27,16,
given in Table 2, Z:4, sp.gr. calculated 4.84, determined 4.83' Cell
constantsgiven by Kedesdy et al. (1957) (locality not stated), Klingsberg
and Roy (1959) (Chisholm, Minn.), and Evans (this paper) (Lower
California) agree closely with Bystrtim's. The only discordant values are
those on a sample from Giiziirem, Ere{li region, Turkey, published in an
abstract by Schrcider(1952), who stated that he obtained them from
powder data that agreed closely with those published by Fleischer and
Richmond (1943). Schrcider'sunit-cell constants,given in Table 2, show
no apparent relation to those of other investigators and give a calculated
density ol 4.346, in good agreement with his own determined value'
4.370.More detailed data have not been published.We are unable to explain theseresults.
Crystals of ramsdellite have not previously been described, although
X-lingsbergand Roy (1957) mention crystals as much as 6 mm long from
Chisholm, Minnesota. What appeared to be single crystals of ramsdellite
were found on samplesfrom the Gavilan Mine, Lower California, Mexico,
kindly given to us by James A. Noble. The samples consist of massive
plumboan hollandite,with the surfaceincrustedby crystalsof ramsdellite
and with apparently excellent single crystals, a few tenths to two mm in
size, in fissuresand cavities. When examined by Evans in 1958, these
crystals proved to be pseudomorphsof ramsdellite after groutite. Fig. 1,
RAMSDELLITE,
ORTHORHOMBIC DIMOKPH OF PYROLUSITE
51
Tlsr,B 2. Cnr,r,Coxsrmtrs (rN A) or Rlusonr.r-rrr nNo Rrr,atao PHASEs
Reference
Material
Ramsdellite
4.5
Ramsdellite
Ramsdellite
Ramsdellite
Ramsdellite
Ramsdellite (strong phase)
Ramsdellite (weak phase)
Groutellite
Groutite
Groutite
Groutite
Gamma-MnO:
4.533
6.374
4.528
4.52
4.53
4.61
4 .7I
4.58
4.56
4.56
4.46
Gamma-MnOz
Gamma-MnO:
Gamma-MnOz
Gamma-MnOz
Gamma-Mnor eu(OH)o04
Gamma-MnOr sr(OH)o os
Gamma-MnOr.zn(OH)o.ze
Gamma-MnOr *(OH)o 36
Gamma-MnOr.*(OH)os
Rho-MnOz
4.418
4.450
4.470
4.489
4.42
4.43
4.49
4.51
4.54
4.453
2.83
Richmond (in Fleischer,
9.27
t0.126
9 .285
9. 2 7
9.28
9.54
9.52
10.76
1 0 .7 0
10.00
9 32
2.866
4.092
2.866
2.87
2.86
2.88
2.89
2.85
3.03
2.850
Bystrdm (1949)
Schrdder(1952)
Kedesdy et al. (1957)
Klingsbergand Roy (1959)
Evans, this paper
Evans, this paper
Klingsberg and Roy (1959)
Collin and Lipscomb (1949)
Gruner (1947)
Klingsberg and Roy (1959)
Kondrashev and Zaslavskii
9 51
9 305
9.336
9.391
9.70
9.70
9.79
9.93
10.20
9.396
2.8t1
2.850
2.848
2.848
2.790
2.79t
2.820
2.8+o
2.85e
2.827
Kedesdy et al. (1957)
de Wolfi (1959)
de Woltr (1959)
de WoIfi (1959)
Feitknecht et al. (19ffi)
Feitknecht et d. (1960)
Feitknecht et a). (1960)
Feitknecht et,al,. (196O)
Feitknecht et al. (196O)
Kedesdy et al'. (1957)
9.2
reM)
(1es1)
2, (from Lake Valley), and 3 show three typical forms. The wheel-shaped
crystal (Fig. 3) is very similar to a crystal of groutite figured by Gruner
(1941). Professor Paul Ramdohr has kindly called our attention to the
similarity of Fig. 1 to a drawing of a crystal figured as "pyrolusite" in
Dana's Systemof Mineralogy, 5th Ed., 1868,p. 165.
The facesgave poor signalson the goniometerand were not measured
accurately; ,tulll}l was prominently developed on most crystals and
o t h e r f a c e s i d e n t i f i e dw e r e D { 0 1 0 } , o [ 1 0 0 ] , c { O O t } ,/ { 0 1 1 } ' y l l 2 } l ,
fr{130
, e} l \ 2 r l ,Q l 2 4 r l .
Buerger precession patterns gave a unit cell identical with that of
Bystrdm (1949), but a second, less prominent lattice was also present'
similar to that of ramsdellite, but with a slightly larger unit cell. The
m e a s u r e dl a t t i c e c o n s t a n t sa r e ( i n A ) :
Strong phase (Gavilan Mine)
Lake Valley (Bystrdm, 1949)
Weak phase (Gavilan Mine)
9 . 2 8 + 0 . 0 3 2 . 8 6+ 0 . 0 2
4 . 5 3+ 0 . 0 2
4.533+0.0059.27X0.01 2.866+0.005
4 . 6 1+ 0 . 0 4
9 . 5 4 + 0 . 0 5 2 . 8 8+ 0 . 0 3
52
M. FLEISCHER, W. E. RICIIMOND AND II. T. EVANS, JR,
Frc. 1. (Left) Ramsdelliteafter groutite,GavilanMine, Lower California,Mexico.t {010},
m lll0l, y ll20l, J [011]. Drawing by Evans.
Frc.2.(Right)
nu-.d"rft
]' nt'{rt't,
",ffi -d.[lt,.tjl;I?';i il",:J*tco.b [010
The patterns were somewhat diffuse for both the strong and weak phases.
Traces of a pattern due to a pyrolusite lattice in parallel orientation were
also present on the photographs; this lattice is oriented so that the tetragonal a, b:a, and c axes of pyrolusite are parallel to the orthorhombic
a, b, and c axes,respectively, of ramsdellite.
The ramsdellite crystals are therefore pseudomorphs after groutite,
Iike those found by Klingsberg and Roy from Chisholm, Minnesota, and
are formed by the oxidation reaction aMnO(OH)*Or--+4MnOz+2H2O.
Exactly the same reaction is involved in the conversion of manganite to
pyrolusite. Pseudomorphsof pyrolusite after manganite (MnO(OH)) are
well known. Another example,found at Lake Valley, New Mexico, is
shown in Fig. 4. The *-ray pattern of the pyrolusite crystal shown exhibits
the same kind of difiuseness as that of the ramsdellite pseudomorphs
from Gavilan Mine. These conversions are readily understood on the
basis of the crystal structures of the phases involved. The structure of
ramsdellite is essentially similar to that of groutite, so that the latter can
transform to the former by a diffusion of the hydrogen atoms to the surface of the structure, where they react with atmospheric oxygen, while
only minor adjustments are required for the positions of the manganese
and oxygen atoms. A similar controlling structural relationship exists between manganite and pyrolusite. Such an alteration processmay be expected to disturb the periodicity within the large crystals sufficiently to
account for the difiusenessof the r-ray photographs of the altered phases.
RAMSDELLITE,
ORTHORHOMBIC DIMORPII OF PYROLUSITE
53
Ftc' 3. (Left) Ramsdellite after groutite, Gavilan Mine, Lower california, Mdxico. c
[001],
, {010}, a [100], m lll0l, e {130}. Drawing by Evans.
Frc. 4. (Right) Pyrolusite pseudomorph after manganite, Lake Valley,
New Mexico. Drawing by Evans.
The hypothesis of alteration also parallels that proposed for the pair
montroseite [Vo(OH)]-paramontroseite (VOz) by Evans and Mrose
(1955)' They also found one or more intermediate phasesbetween montroseite and paramontroseite, similar to the weak phasereferred to above,
and suggestedthat the intermediate phase might be a partia[y dehydrogenated step between the two end phases.Klingsberg and Roy (1959)
found an intermediate phase, which they named groutellite, to be formed
in the reduction of ramsdellite to groutite, but not in the reversereaction.
Their cell constants are given in Table 2; they are croserto those of the
weak phase of the ramsdellite from Gavilan Mine than to those of ramsdellite proper.
The published *-ray powder patterns of ramsdellite give spacings in
good agreement,lexcept for one sample studied by Allsman (1955).The
strongest lines are listed in Table 3, along with measurementsfor
"Nsuta MnO2" and grouteilite. It will be noted that the spacingsgiven
I The patterns of 2 samples from
czechoslovakia given by Bernardova and Sransky
(1960) also are in good agreement with Nos. 1-6 of Table 3.
M. FLEISCHER, W E. RICHMOND AND H T. EVANS' JR
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RAMSDELLITD, ORTHORHOMBICDIMORPH OF PYROLUSITE
55
for sample No. 7 differ distinctly from all the others and are very closeto
those of the "Nsuta Mno2" of Soremand cameron (1960) the material
;
is probably not ramsdellite.
The relation of ramsdellite to the synthetic compounds called gammaMnoz and rho-Mno2 and to the naturally occurring material called
Nsuta Mnoz is a very important problem becauseof their extensiveuse
in dry cell batteries. It is evident from the cell constantsfor these materials,listed in Tabre 2, that they are closelyrelated,but the various investigators have disagreedmarkedly on the nature of the relationship and
the details of the structure of gamma-Mnoz. No further discussion is
given here; the problem is discussedwith many referencesby sorem and
Cameron (1960),and new data are also given by de Wolff (1959),Nye et
al. (1959), and Feitknecht et al. (1960). The Swiss workers formulate
gamma-MnO2,not as a defect structure, but as MnOz_,(OH),, with n
ranging from nearly zero to a maximum of 0.54, and find a straight line increase of total cell volume from nearly anhydrous gamma-Mno2 with
increasingn, which when extrapolated, falls closeto the value for groutite
(": r).
Pnvsrcar, PnoppnrrBs
Ramsdellite is steel-gray to iron-black in color. The streak is given as
black by Fleischer and Richmond (1943) and by Klingsberg and Roy
(1957), but Ramdohr and Franzel (1956) srate emphatically that the
streak is reddish. New trials on material from Lake valrey and Gavilan
Mine showed that nearly all samplesfree of iron oxide gave a dull brack
streakl a few gave black streaks with a slightly brownish tint. The hardness is variable, 2-4, mostly about 3. specific gravities measured are
4.73,4.65,4.83 (Lake Valley), 4.37 (GOzdrem,Turkey, Schrcider,l9S2);
calculated from Bystr<im's r-ray data assuming the composition Mnoz,
4.84. Cleavageson three pinacoids and a prism (Ramdohr and Frenzel,
1956) commonly give the mineral the appearance in hand specimen of
overlapping platelets; in polished section it commonly appears to be
finely fibrous. Optical data in reflecting light are given by Ramdohr and
Frenzel(1956)and by EI Shazlyand Saleeb(1959).
OccunnBNcBs
Verified occurrencesof ramsdellite are. U.S.A.: Lake Valley, Sierra
County, New Mexico; Monroe-Tener Mine near Chisholm, Minnesota
(Klingsberg and Roy, 1957);Idorado Mine, Colorado (Kulp and perfetti,
1950); Bannock County, Idaho (Allsman, 1955); Blythe, California;
Canada, East River, Pictou County, Nova Scotia; Mexico, Gavilan
Mine, Lower California; Czechoslovakia,Horni Blatna (platten) and
56
M. FLEISCHER,W.E. RICHMONDAND H. T. EVANS' TR.
Piebuz, Bohemia (Bernardova and Slansky, 1960); Turkey, Kodjas
Karil Mine, Roumelia, (Fleischerand Richmond, 1943),and perhapsat
Giizijrem (Schriider, 1952); Egypt, Yoider, Gebel To Yu, and Um Bogna
(EI Shazly and Saleeb,1959); India, Dongri Buzurg and Sandur (Mukherjee, 1959).No doubt many more occurrenceswill be found'
The manganese deposits at Lake Valley have been described by
Creaseyand Granger (1953).Ramsdelliteoccursin fissuresand faults in
limestonel most of the samples came from a few pockets in the Stone
Cabin fissure,which is marked on their map. Most commonly it occurs as
groups of crystals (Fig. 5) on highly ferruginous chert; less commonly as
"nail-head ore" (Fig.6). Much of the ramsdellitehas inverted to pyroIusite; portions of a single crystal may give the r-ray pattern of ramsdelIite or of pyrolusite or of a mixture of the two.
Ramsdell's type specimen, from an unknown locality, is mostly massive, but partly platy; it occurs on a light brown chert distinctly different
from that at Lake Valley. The specimen from East River, Nova Scotia
(U. S. National Museum C1724) consistsof fine platelets of ramsdellite,
entirely surrounded by coarse blades of pyrolusite. The specimen from
Blythe, California, is an irregular nodule approximately 3 by 2 inches,
with an outer rim I/16 to f inch wide of fine-grained psilomelane,the interior consisting of a mixture of finely crystalline ramsdellite and pyrolusite.
The origin of ramsdellite and pyrolusite as weathering products of
groutite and manganite, respectively, can be explained on a crystal
chemical basis as described above. Pyrolusite is recognized as the stable
form of MnOr and presumably can also be formed as a primary mineral
but it is possible that ramsdellite, like paramontroseite (see Evans and
Mrose, 1955),is actually metastableand can be formed only by the oxida-
Frc. 5. (Left) Ramsdellite, group of crystals, Lake Valley, Nerv Mexico.
Frc. 6. (Right) Ramsdellite, "nail-head spar," Lake Valley, New Mexico'
RAMSDELLITE, ORTHORHOMBICDIMORPH OF PYROLUSITE
57
tion of groutite. The apparently universal presenceof pyrorusite in varying amounts disseminated in ramsdellite in oriented position suggests
that ramsdellite undergoesfurther, slower (reconstructive) alteration to
pyrolusite as the more stable phase.Ramsdellitehas not so far been observed in a mineral associationthat would suggestit to be of primary occurrence, that is, deposited directly from mineralizing solutions. There is
as yet no evident clue in the observedoccurrencesas to the specificconditions that causethe formation of manganite rather than groutite and vice
versa' Further attempts to synthesize these compounds are desirable.
AcruowrrpGMENTS
we are indebtedto our colleaguess. c. creasey,who colrectedthe samples from Lake valley and gave us data on the occurrence,K.
J. Murata
and Nancy M. Conklin for spectrographic, Charlotte M. Warshaw for
chemical,and J. M. Axelrod ior x-ray analyses;to L. S. Ramsdell who
loanedus his type specimen,and to J. A. Noble for the gift of the samples
from the Gavilan Mine. The photographs were made by Anthony M.
Denson.
RnrunnNcns
Ar,r,sue'r, P' L. (1955), oxidation and enrichment of the manganese deposits of Butte,
Montana. Thesis, Montana School of Mines. o. l-93.
Benne'ruova, E. ,rNo E. Sr,tNsr<v (1960), The o..or."n." of ramsdenite in czechoslovakia.
V estnik u slr ed..ustaau geol,.,35, 153- 154 (Engl. summ. .
)
Bvsrndu, A. M. (1949), The crystal structure of ramsdellite, an orthorhombic modification of MnOz. Acta Chem. Scand., 3, 163-173.
carr,r.inn, srlroNNa axn Fn.rNcors Knaur (1954), comportement thermique de quelques
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Manuscript receitetl March 17, 1961.