AmericanMineralogist,Volume77, pagesI i,33-1143'1992
Structural chemistry of Mn, Fe, Co, and Ni in manganesehydrous oxides:
Part I. Information from XANES spectroscopy
Ar,.q.rNM,q,Ncrau*
place Jussieu,
Laboratoire de Min6ralogie-Cristallographie,Universit6s Paris 6 et 7, CNRS UA09, Tour 16, 4
75252Pais Cedex05, France
ANaror-n I. Gonsmov
prospekt,
Institute of Ore Geology and Mineralogy (IGEM) of the USSR Academy of Science,35 Staromonetny
109017Moscow,Russia
Vrcron A. Dnrrs
Geological lnstitute of the USSR Academy of Science,7 Pyzhevskyprospekt, 1090I 7 Moscow. Russia
AssrRAcr
The oxidation state and coordination number of Mn, Fe, and Co in hydrous manganese
oxides have been investigatedby high resolution XANES spectroscopy.At the MnK edge,
spectral sensitivity is high enough to differentiate between Mn ions of different oxidation
statesand site octupations. Application of this technique to various poorly crystallized
goehydrous oxides, including samplesof birnessite,vernadite, asbolane,and manganese
present,
are
ions
Mn
thite, indicatesthat Mn atoms are generallytetravalent. If low-valence
they certainly make up lessthan 20 ato/o.Innatural Fe-containingvernadite, Fe atoms are
ions of about l0 at0l0.Co
sixfold cooriinated, on the basis of a detection limit for t4lFe3+
has been found to be trivalent in both cobalt and cobalt nickel asbolane.MnK preedge
spectrahave also been demonstrated to be sensitive to the local structure of tetravalent
manganate.Spectralintensity was found to depend on the ratio of edge-to corner-sharing
MnOu octahedra: the larger the tunnel size of the manganate,the lower the intensity of
the preedge.Application of this concept to the structure of 6-MnO, suggeststhat vernadite
contains ur *utty corner-sharingoctahedra as todorokite. On the basis of XANES data,
6-MnO, does not possessa layered structure and should not be consideredas long-range
disordered birnessite.
INrnonucrron
In mineral structures,Mn, Fe, and co atoms can occur
in a number of oxidation statesand sites.For;;,;;;;,
Mn2+, Mn3+, Fe2*, Fe3*, and co2* ions can b. i;fi;
both octahedral and tetrahedral coordinationr,-*tr"r"ur
Mna+ and low-spin co3+ are resrrictedro ocrahed;i;rcs.
Anundersrandingoftheelecrronicstructure"f.;;;;1;
minerals can be important for constrainlne r,-"1;iui"i":
ilterpretations from X-ray diffraction (XRD) d",".;;;
formation is particularly useful for elucidating th;;;ture of poorly crystallized hydrous .*10., # *ftlt
diffraction intensity data fail to provide u.r.rlq.r"'r'or"u:
tion. For example, several models have been ;;;o;;
for the structure of ferrihydrite. Some ..r"u..ti#tiu.rl
found only sixfold-coordinated Fe uro-, Oo*.'?rro
Bradley, 1967), whereasothers have reported ,rgtin*t,
fi[ing of tetrahedral sires, 330/oby Eggleton
""i";;;;:
rick (1988) to 50o/oby Harrison et al. (1967).I";;i;;.
insrance, chukhrov er al. (1988) interpreted xR;";;;;
from iron vernadire by assuming the presence;f"J;;;
one-third of (Fe,Mn) atoms in fourfold .oorai,r#ol'l""'
3g041Grenoblecedex,France.
/tlr2-l I 33$02.00
0003-004x/92
The purpose of this work is to more accuratelydeter-i1e^th9 oxidation state and site occupation of Mn' Fe'
and Co.in various hydrous manganeseoxides by using
near-edgestructure (XANES) spectrosll"y
This crystal chemical information provides concopy' Xb.::tption
structural data obtained for the
:iti]lt: ll-l"terpreting
using XRD' selectedarea electron dif:"-.9
Tif:*ls
(SAED)'
energy dispersive spectrometry @DS)'
fraction
and extended X-ray absorption fine structure (EXAFS)
These results are presentedand discussed
:p::troscopy'
part
of this paper (Manceau et al'' 1992)'
in the.second
are usually separatedinto two parts:
..Yy:^spectraand the main-edge regions (Brown et al''
111:t":9c"
1988)' The former is located to the lower energy side of
absorption edge and correspondsto ls
tnt,tt".-"*:sing
- 3d type.electronictransitions' The latter extendsfrom
volts above the preedgeto about 50 ev
1.t* :l:toon absorptionedgeand correspondsmainlv
the
It$llf
of photoelectronseject9,T*t*:-:tcatteringresonances
low kinetic energv' Apte and Mande (1982) and
ld.yittr
found that the enersv of the main-edge
:l
it,!1n80)
peaks
"ttlt preedge
of manganeseoxides varied linearly
and
ergy shift with increasingvalence results partly from in-
I133
I 134
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
creasedattraction between the nucleus and the ls core
electrons and partly from the effect of final-state wave
functions. Final states of 3d character (preedgeregion)
are more tightly bound and hence are less sensitive to
changesin ionicity and in solid-stateeffectsthan the more
diffuse, higher energy,final statesof the main absorption
K edge (multiple-scattering region). Thus, the oxidation
state is more reliably determined from the energy position of the preedgepeak than from that of the main absorption edge spectrum. Belli et al. (1980) reported that
although molecular orbital (MO) transition assignments
are qualitatively correct for interpreting main XANES
features, solid-state effects are also important. If confirmed, such spectral sensitivity to the manganeseoxide
structure would be of particular interest; it would allow
MnK XANES to complement EXAFS spectroscopyfor
the determination of the local structure of hydrous man_
ganeseoxides. FeK XANES spectraof minerals have been
more extensively studied. Near-edgeand main-edge ab_
sorption features from FeK XANES spectra have been
shown to reflect the site geometry and valence of Fe in
minerals(Calasand Petiau,1983;Waychunaset al., l9g3).
More recently,Manceauet al. (1990a)applied this spectroscopy to test the possible presenceoftetrahedrally co_
ordinated Fe3+in hydrous iron oxides. In this case,FeK
preedgefeatures were shown to be particularly sensitive
to the t61Fe3+/l41Fe3+
ratio with a detection limit f61 rrtpsr+
ions at less than l0 ato/o.In minerals, Co can be divalent
or trivalent, tetrahedrally or octahedrally coordinated, and
in a low-spin or high-spin configuration. Facing these
contrasting electronic structures, XANES spectroscopy
should yield valuable information about the crvstal
chemistry of Co in hydrous manganeseoxides.
ExpnnruBNTAL DETATLS
Analytical techniques
XANES spectra were obtained at the EXAFS IV sta_
tion at the LURE synchrotron radiation laboratory (Or_
say, France).The electron energyofthe DCI storagering
was 1.85 GeV, and the current was between 200 and250
mA. The incident beam was monochromatizedusingpairs
of reflecting Si (5 I l ) crystals so that the Bragg,angle near
the MnK edge was near 66.. At this angle, the energy
spread due to vertical divergence of the beam was 0.45
eV, and the intrinsic width of the reflection curve (Dar_
win width) equaled 0.05 eV. These widths are signifi_
cantly smaller than the Mn core-levelwidth 0.16 eV)
that resultsfrom core hole lifetime. The overill resolu_
tion of XANES spectrawas equal to the convolution of
the instrument with the coreJevelwidths and was as small
as 1.2-1.3 eV. With this high level of resolution,exper_
imental spectral broadening was negligible. Harmonics
due to higher order reflectionswere filtered out with bo_
rosilicate glass mirrors (Sainctavit et al., lggg). The en_
ergycalibration of MnKXANES spectrawas made taking
a maximum of the preedgepeak for MnCrrOo at 653g.7
eV. The preabsorption feature in MnCrrOo was repear_
edly measuredto monitor the stability of the energy calibration. Mn and Fe preedge spectra were recorded in
stepsof 0.06 and 0. l3 eV, respectively.
Corrected preedge absorption structure was obtained
by subtracting the arc-tangent-fitted interpolated tail of
the main edgefrom the observedspectra.The absorbance
was then normalized with respectto the absorptionjump
of the main edge (Ap). This jump was determined by
fitting first-order polynomials to the data 100 eV below
the preedgeand from 100 to 400 eV above. The difference between these two lines (at the energyat which the
preedgestarts) was used as the normalization factor for
the correctedpreedge.The reliability of the experimental
measurementsand our analytical treatment were confirmed by recording several spectra of the same sample
during differentbeam sessions.
Materials
A seriesof well-crystallized manganese,iron, and cobalt oxides, which served as referencecompounds, and
other Mn-, Fe-, and Co-bearing minerals were analyzed.
The minerals are listed in Table I along with their formulae and selectedcrystallographicdata.
Birnessite.A syntheticbirnessitesample,NaoMn,oOrr.
9H,O, synthetized by Giovanoli (Giovanoli eI al., 1969,
1970a, 1970b; Giovanoli and Stahli, 1970) was examined, in addition to two natural birnessite samples (Bl,
Ml2) from (Fe,Mn) micronodulesof the Clarion-Clipperton province, Pacific Ocean(Chukhrov et al.,1978a;
Shterenberget al., 1985).SampleBl containsMn (MnO,
: 67.66 wto/o)and, in addition, Mg, K, Na, and Ca (MgO
:8.58 wto/0,K,O :2.43 wtol0,NarO: 1.90wto/0,and
CaO: 0.52wto/o).A noticeablefeatureof sampleMl2 is
the absenceof Ca, Mg, K, and Na and the presenceof
small amountsof Ni, Cu, and Co (NiO : 1.650/o,
CuO :
0.920/o,
and CorO. :0.160/o).
Vernadite. A synthetic vernadite sample (d-MnOr) was
prepared by adding HrO, to a stirred I M KMnO, solutron at room temperature(Chukhrov et al., 1987).The
precipitate was freeze dried, then washed with O.l M
HNO3, distilled HrO and finally I M NaCl. A large collection of Fe-bearing natural vernadite samples previously studiedby Chukhrov et al. (1987, 1988)and Manceau and Combes (1988) were examined further. Data
from EDS indicated that the Mn/Fe ratio in thesenatural
particlesrangedfrom 3/l to l/1.
Mn-bearing goethite. A sample of manganesegoethite
from the Fe-Mn crusts of Krylov Underwater Mountain
(Atlantic Ocean) has been described by Varentsov et al.
(1989) as goethite groutite. Our EDS data showed the
mean composition of particles to be about 500/oMnO,
and 500/oFerOr, but with a variable MnO, content ranging from 33 to 620/0.
Asbolane. Three asbolane samples were investigated.
Two cobalt nickel asbolanesamplesfrom New Caledonia
Ni ore deposits were previously studied by Manceau et
al. (1987) using EXAFS spectroscopy.A cobalt asbolane
sample from Saalfeld (Germany) was originally charac-
I 135
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
Trele L
Selectedmineralogicaland crystallographicinformationon samples
ldeal comoosition
Mineralname
Oxidation state and site
occupation of cation
Full point group
Manganese oxides
Phyllomanganates
Buserite (2-D)
Lithiophorite(2-D)
Birnessite(2-D)
Asbolane (2-D)
Chalcophanite(2-D')
Vernadite (2-D')
Tectomanganates
Todorokite
Psilomelane(romanachite)
Hollandite
Ramsdellite
Pyrolusite
Other
Rhodochrosite
Manganesespinel
Hausmannite
Feitknechtite
MnO,
(Al,Li)MnO,(OH),
Na*Mn,nO.r.9HrO
nH,O
Mn(O,OH),(Ni,Co),(O,OH),'
ZnMn.O,.3HrO
6-MnO,
t6lMn4+
16lMn1+
(Na,Ca,K)o
s,(Mn,Mg)6Olr.nHrO
(Ba,HrO)rMn501o
(Ba,Na,K)Mn"(O,OH),u
a-MnO,
MnO.
16lMnl+
MnCO.
Mncrroo
Mn.O.
B-MnOOH
16lMn2+
I6tMnl+
16lMn1+
16lMn1+
16lMna+
t6tMn4+
16lMn4+
16lMn.+
l6lMn.+
I4tMn2+
I6lMn3+ + I11Mn2+
t6lMn3+
llon oxides
t6lFe3+
Goethite
Akaganeite
Lepidocrocite
Feroxyhite
Ferrihydrite
Hematite
Maghemite
lron phosphate
a-FeOOH
B-FeOOH
"y-FeOOH
d-FeOOH
5Fe,O3.9H,O
a-FerO.
1-Fe.O"
FePO4
Erythrite
Cobalt spinel
Heterogenite
Co compounds
Co.(AsOoL.SHrO
CoAl,On
CoOOH
totFe3*
r6tFe3+
rorFeF*
rerFeF*
L6lFe3+
I6lFe3+ + I4lFe3+
14tFe3+
torCcl2*
rrrCd*
rorCd*
-0)
C2,, Ca(2)
Cr,(3)
-(4)
C,(5)
-(6)
C"'{71
Crr(8)
c2n, c4h19)
D."(10)
D."(11)
4"(2)
ol13)
o"(13)
{14)
D",(15)
Dr,(l6)
D2h/d71
D.118)
-(19)
D.120)
o,l21l
4e2)
--(23)
oh(l3)
D6'124)
5:Wadsley(1953)'P,o-st
4:Drits(1987);
(1980a);
3:PostandVeblen(1990);
2:Wadsley(1952),PaulingandKamb(1982);
Note:1:ciovanoli
Turnerand Post(1988);
(19S8):6:Chukhrov et dt.'1tSZbO1,
Gioianoli(19806);7:Post and Bish(1988);8:Wadslel (195.31
and Appteman
12= Effenbergeretal.
Postet a|.41982),
Miura(1986),
Vicatet al.(1986);10: Bystrom(1949);11: Baur(1976);
S: eydtrOm
andeysirom(1950),
(19351;
18: Patratet al.(1983);
(1065);iS: Szftuta6t d. (tgOg);i6: Szytulaet al.(1970);17: Erying
(1981i;13: Hiilet at.(197i);14': Bricker
(1958);
(1Si67);
21 :Hegg'(1935),Venivei(1935);22:Arnold (1986);23:Taylor and Heiding
20:Btaki et it. (tSeO);
ig:io*e and Bradtey
(1973).
andGoethals
et al.(1969),Deliens
24: Delaplane
terized by Chukhrov et al. (1982a)by X-ray and electron
diffraction, EDS and XPS. The cation composition of the
last has Mn. Co. and Ca in the ratio l:0.63:0.12.
Rrsur,rs
MnK preedge
site, four todorokite, and two psilomelane samplesfrom
different localities showed that the chemistry and origin
of the minerals had no influence on spectral shape.We
conclude that the intensity and shapeofa preedgespectrum depend only on the structure of the manganeseoxide mineral and that this information can be used on a
phenomenologicbasis to assessthe local structure ofunknown structures. Preedgesp€ctra of unknown samples
are compared to those of the referenceminerals in Figure
3. The energyof the preedgepeak is the same as those in
tetravalent manganates,and the intensity is always found
to lie between those ofbuserite and todorokite.
Preedgespectrafor some of the referencecompounds
are presentedin Figure la. A shift in the preedgetoward
higher energy occurs with an increase in the oxidation
state of Mn in the mineral regardlessof the coordination
number. Spectrafor severalmanganeseoxides are shown
in Figure lb. There is a changein intensity and full-width
at half maximum (FWHM) for the preedge peaks that MnI( main edge
Main-edge spectrafor some of the Mn referencecomdirectly reflects progressivechangesin structure. As the
size ofthe tunnel ofoctahedra increases,the preedgein- pounds are presentedin Figure 4a. The main edgeshifts
tensity and FWHM decrease(compare Fig. 2 with Fig. toward higher energy with increasing formal oxidation
1b). This rather unexpectedrelationship was verified by state of Mn ions. The steeply rising part of the XANES
recording these spectra several times at different beam spectraofmanganatesand hydrous manganeseoxides apsessions.Variations were not due to a preferential ori- proximately superimposesupon that of pyrolusite (Fig.
entation of the powder in the polarized X-ray beam (i.e., 4b, 4c). However, the spectral shape and, more specifitexture effect) as shown by recording spectra of several cally, the edge-crestintensity, progressivelyincreasefrom
samples at the "magic angle" (Manceau et al., 1990b). pyrolusite to buserite. This is opposite to the trend obAdditionally, comparison of the spectra of two pyrolu- served for the preedgespectra.
I 136
MANCEAU ET AL.: MANCANESE HYDROUS OXIDES I
0.14
IU
o
z
o 0.09
pyrolusite
tr
Ic0
tr
tr
o
bus€rite
chalcophaniae
todorckite
0.04
z
psilomelm
6536
6539
6542
6545
ENERGY (eV)
6548
0.09
uJ
pyrolusite
o o.o7
z
ramsdellite
o
hollandite
cr
o
a
0.05
o
hollandit€
ramsd€llite
pymlusiae
Fig. 2. Schematicstructureof MnO, polymorphs.phyllomanganates
haveno (2-D) or few (2-D,)cornerlinkagesof Mn
octahedra.
This family includesbuserite(2-D),lithiophorite(2_
D), asbolane
(2-D),chalcophanite
(2-D,),and birnessite(2-D or
2-D').Tectomanganates
havemanycornerlinkages
and 3-D O
framework.Theyare built of singleto multiplechainsof edgesharingMn octahedra.
ThesechainsarecrossJinked
by corners,
resultingin tunnelstructures.This family includestodorokite,
psilomelane(or romanachite),
hollandite,ramsdellite,and pyrolusite.
0.03
E
2 o.or
our data show a significantly larger shift. This is demonstrated,for example,by the 1.5-eVdiference between
Mn2+ and Mna* ions in comparisonwith a few tenthsof
an electron volt reported by Belli and coworkers.We can
6536
6539
6542
6545
6 5 4 8 speculatethat lower spectral resolution in the older experiments has reducedthe precision of the determination
ENERGY (eV)
ofpreedge energies.
The intensity of the preedgespectrum for MnCrrOo is
four times greater than that for MnCO, (Fig. la). The
data agreewith the general observation that in a tetrahedral environment preedge spectra are four to seven
times more intense(see,e.g.,Lytle et a1.,1988).The enhancedintensity can be explainedby dipole selectionrules,
Fel( XANES
although a weak contribution of quadrupole transitions
The FeK preedge spectra for some t41Fe3+
and t61Fe3+ has been experimentally demonstrated (Driiger
et al.,
referenceminerals are presentedin Figure 5a. Figure 5b
1988;Poumellecet al., l99l). Allowed dipole transitions
and 5c show the spectraofvernadite comparedto those
from the ls level must have a final wave function with p
for referenceminerals and simulatedcompositionsr4tFe3+
/ symmetry. Therefore, a major part of the preedgeis
usu(t6lFe3++ t4rFe3+)
using linear combinationsof goethite ally
ascribed to electric dipole transitions to p-like states
and FePOospectra.
hybridized with 3d states.The ligand-field induced p-d
mixing is symmetry dependent,and Brouder (1990) has
CoKXANES
recently demonstratedthat the transition strengthis ruled
The CoK main absorption edge spectra from some
I6lCo2*(erythrite), tot6qr* (CoAlrOn),and t6rco3+(Co- by the full-point group symmetry of the crystal: it is negligible or intensedependingon the centrosymmetryof the
OOH) referenceminerals are presentedin Figure 6 along
full point group. For example, the low preedgeintensity
with that of the Saalfeld cobalt asbolane.The spectrum
of sixfold coordinatedMn2+ ions in MnCO. resultsfrom
of asbolaneis featurelessand resemblesthose of erythrite
the existenceof an inversion center inthe Dro full point
and CoOOH. The main-edge energy for asbolaneis the
group (Table l).
same as that of CoOOH, but it is larger than that of
Comparison of the preedge spectra from MnCrrOo
erythrite.
(t4rMn2+)and MnCO, (r6iMn'z+)
shows that for a given
oxidation state, the FWHM decreaseswith a decreasein
DrscussroN
coordination number. Similarly, comparison of spectra
Interpretation of spectrafrom referencecompounds
from MnCOr, p-MnOOH (t6rMn3+)
and B-MnO, (t61Mn4+)
The Mn preedgespectra(Fig. l) show a chemical shift indicatesthat for a fixed coordination number, the preedge
that relates to the oxidation state of Mn in the mineral. FWHM increaseswith the oxidation state. This increase
A shift was previously noted by Belli et al. (1980), but in line width as coordination changesform four- to six-
tl37
MANCEAU ET AL.:MANGANESE HYDROUS OXIDES I
0.07
0.07
lrJ
o
z
0.05
dl
.E
o
0.03
U)
o
E
o
z
Lu
z
(n
r,n)
(f
(J
o
E
o
z
6542
ENERGY(eV)
o
z
lr,J
0.05
o
z
0.03
d)
6545
6548
6539
6542
ENERGY(eV)
6545
6548
0.05
0.03
;E
E
z
6542
ENERGY(CV)
ao
tr
o
a
tr
o
6539
0.07
d)
@
0.01
6545
0.07
lu
0.03
fo
0.01
6539
0.05
o
0.01
-0.01
6536
z
6539
6542
ENERGY(eV)
6545
6548
0.01
- 0 . 01
6536
Fig. 3. MnK preedgespectraof samplesand referencematerials compared with spectraof buseriteand todorokite. (a) Asbolane
from Germany and manganesegoethite; (b) d-MnOr, (c) vernadite, (d) birnessite.
fold, and from Me'+ to Me("+r)+,is consistentwith the
ls-3d type of assignmentbecausethe line width reflects
the ligand field splitting of the 3d orbitals. For example,
t61Mn3+
is a Jahn-Teller ion and the splitting of the individual orbital statesis largeenoughthat the preedgespectrum of p-MnOOH is separatedinto two well-resolved
absorption bands.
In lepidocrocite, goethite, and akaganeite(Fig. 5a) ls
- 3d absorption is weak, only about 3-40loof the intensity of the absorptionj ump. The slightly increasedintensity of the preedgespectrum of hematite in comparison
referencecompounds is anomwith those of other t61Fe3+
alous, since the spacepoint group of hematite (Dro) and
the Fe site symmetry 6m) areboth centrosymmetric.Increasedintensity may result from long-rangeorder effects,
which are known to influence preedge characteristics
(Driigeret al., 1988).In the caseof FePOo(rorFe'*),a lack
ofinversion center at the Fe site is reflectedby the fivefold higher intensity for the preedgespectrum.
Oxidation state and site occupationof Mn
All of the preedgespectrafor hydrous manganeseoxides (vernadite, D-MnOr, asbolane,birnessite) are found
at the same energyas those of manganeseoxides (Fig. 3),
suggestingthat the range of valences for Mn atoms is
limited. This interpretation is corroboratedby main-edge
energy data (Fig. 4b, 4c). The absenceof compelling evidence for large amounts of Mn3* and Mn2+ in any of
these manganeseoxides agreeswith recent studies. Indeed, even though it has long been assumed that Mn
atoms in manganateswere divalent and tetravalent, numerousXRD studies(Postet al., 1982:Giovanoli, 1985;
Tamada and Yamamoto, 1986; Vicat et al., 1986; Post
and Bish, 1988;Post and Appleman, 1988),XPS studies
(Murray and Dillard, 1979;Chukhrov et al., 1982b;Dillard et al., 1982), and redox titration studies (Murray et
al., 1984) have demonstratedthat they are not. The scarcity of low-valence Mn ions is consistentwith the structure ofnearly all tectomanganatesand phyllomanganates,
where the unit-cell parametersof the plane of the octahedral chains, ribbons, and layers are similar. Indeed, if
manganeseoxides contained abundant divalent or trivalent Mn atoms, these heterovalent cations would lead to
significant variations in the unit-cell parameters.
The proportion of Mn3+ may vary from one structure
and one sample to another, but the studies cited above
suggestthat it generally constitutes less than about 200/0.
Given the relatively weak chemical shift between Mn3+
I138
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
uJ
FePO4
maghemite
hematite
g oethite
[!
o 0 . 16
z.
o
z
o
tr
co o . 1 2
(E
8
o
o
U)
E
d 0.04
o
z.
akaganeite
lepidocrocite
co 0 . 0 8
o
z
7108
7110
6530 6540 65s0 6560 6570 6580 6590
ENERGY(eV)
b
IJJ
o
z
buserite
vernadite
todorokite
co
(r
Lll
()
z
dt
(r
o
U)
dt
I
dl
E
o
z
pyro lusite
7112
7114
7116
ENERGY (eV)
7118
maghemite
....
A
0.06
hematite
_
feroxyhi
_ vernadite
0.03
goethite.\
E
o
z
ramsdellite
7 10 8
7110
7112
7114
7116
7118
ENERGY(eV)
6530 6540 6550 6560 6570 6s80 6590 6600
ENERGY (eV)
LU
o
z.
lJl
synth. birnessite
birnessite #M12
o
z
f;
r
o
U)
o
E
zo
dl
(E
_ _
0.06
s i m u l a t i on s
vernadite
o
U)
co
E 0 .o 3
o
z.
goethite
7108 7110 7112 7114 7116 7118
ENERGY(eV)
Fig. 5. FeK preedge spectra. (a) Referenceminerals. From
lowest intensiry to highest: lepidocrocite, akaganeite,goethite,
hematite, maghemite (t6lFe3++ t4rFe3+),
and FePOo(qFer*). (b)
Vernadite spectrum compared with selectedreferencespectra.
Fig. 4. MnK main edgesof manganeseoxides. (a) Reference (c) Dotted lines represent linear combinations of goethite and
FePO. spectra.From lowest intensity to highest:5olo[arFe3+,
compounds: MnCO, (r6lMn,+),MnCrrO. (l4lMnr+),p-MnOOH
100/0
(r6rMn3+),pyrolusite (t61Mn4+).
(b) Evolution of the shapeof the vtpgt+,20o/ot4lFe3r,and 300/0r4tFe3+.
ls - 4p transition in the tectomanganate-phyllomanganate
series. (c) Comparison of D-MnO, spectrum to those of todorokite
and birnessite. Note similarity of d-MnO, and todorokite spec- estimated the detection limit of tatMn2+ions by XANES
to be about l0 ato/o.
lla.
Mn atoms in manganese goethite are also in a tetravalent state (Fig. 3a). This is not surprising because Mn
and Mn4+ preedgespectraand the high variability of their minerals, associated with iron oxyhydroxides in the oxiintensities among tetravalent manganates,our precision dized zone ofweathering profiles or on the sea floor, are
is within this range. We successfullyfitted the experi- exclusively Mna* oxides. Based on an analogy with
the
mental spectrum for MnrOo spinel with a weighted sum large site distortion of Cu2+ (Jahn-Teller ion) in copper
of two spectra: Y:MnCrrOo(t4lMn2+)and %6-MnOOH magnesium phyllosilicates (Decarreau, 1985; Decarreau
(l6lMn3+)(Fig. 7c). On the basis of this result, we have et al., 1992), Mn3+ would be unlikely to enter the goethite
6530 6s40 6550 6s60 6s70 6580 6590 6600
ENERGY(eV)
I 139
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
0.09
lu
z
d)
(f
a
d)
E
o
z
o 0.o7
z
U)
o
1l\\
0.03
;
E
o
z 0.01
6545
(EV)
ENERGY
6542
6539
6536
Fig. 6. CoK main edgespectraof referenceminerals.EryCoOOH (t6rcor+)compared
0.09
thrite ltot6ozt;,CoAlrOn(t4lco'?+),
The amplitudewascaliwith the spectrumof Co in asbolane.
jump asa L!
the atomicpart of the absorption
bratedby assuming
O o.07
z
normalizationvalue.
Local structure of hydrous manganeseoxides
Within the phyllomanganate-tectomanganatesenes,
there is a progressivechangein the intensity and the shape
of preedgeand main-edge spectra (Figs. lb, 4b). Interpretation of the trend is not straightforward and will be
considered,with some details, below.
Preedge. One possibility is that an increase in peak
intensity (from buserite to pyrolusite) correlateswith an
increasein the Mna*/Mn3+ ratio. In order to test this
hypothesis, linear combinations of pyrolusite and
6-MnOOH spectra were computed (Fig. 7a). Although
the shapeand intensity ofthis suite oftheoretical spectra
reproduce the trends observed in the tectomanganatephyllomanganateseries(Fig. l), the simulations shift progressivelyto lower energy as Mn3+ increases.The opposite situation is experimentally observed in reference
minerals and samples:the lower the amplitude, the higher the energyofthe left side ofthe preedgeofmanganates
(Figs. lb, 3). Thus, the preedge spectra of MnO, polymorphs cannot be fitted by a linear combination of Mno*Mnr' referencespeclra.
A secondinterpretation might be attempted using symmetry effects.However, all of the manganeseoxides are
centrosymmetric (Table l), which theoretically precludes
any intensity for the forbidden ls - 3d preedgeabsorption. Thus, it is concluded that the preedgetrend among
tetravalent manganatescannot be qualitatively interpreted within a simple quantum molecular-orbital framework.
A third possibility might explain the trend in terms of
changes in average Mn-O bond distances. In V compounds(Wong et al., 1984)and in sometransition metal
.' . simulations
o
t 0.05
77oO 7710 7720 7730 7740 7750 7760 7770
(eV)
ENERGY
structure in large amounts, thus limiting the extent of the
goethite-groutite solid solution. This explanation may
equally apply to the experiments of Stiers and Schwertmann (1985)and Ebingerand Schulze(1989),who found
that the proportion of Mn3* substitutedfor Fe in goethite
was less than l0 atoloand 14-34 ato/o,respectively.
pyrolusite
ul
b
o
tr 0 . 0 5
o
a
o
0.03
E
o
/
/,,'
Pyrolusite
\
_
6548
'i\
... simulations
(itii\
-.,.1 i
\,\r'..\
\:AN
z 0.01
6536
6539
6545
6542
ENERGY (EV)
6548
0 . 13
IU
O 0 . 11
z
o 0.09
tr
o
a
. . . simulations
0.07
o 0.05
iE 0 . 0 3
MnrOo
pl'/ffi1
o
z
0.01
6536
6539
6545
6542
ENERGY (EV)
6548
+ (g-MnOOH)with selected
2/rt6tMrf
references.
complexes(Kutzler et al., 1980),variations in the oscillator strengthofthe preedgewere attributed to a decrease
in size of the coordination polyhedron. This empirical
relationship between the size of the molecular cage,defined by the nearest-neighborligands, and preedgeintensity was interpreted within a quantum-mechanicalframe-
I 140
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
work (Kutzler et al., 1980;Wong et al., 1984).From that,
it was deduced that the smaller the cage,the higher the
intensity of the ls - 3d transition. Mean Mn-O bond
coordination shells(see,e.9.,the review of Petiau et al.,
1987). In the first of these theoreticalapproaches,the
main absorption maximum is identified as a dipole ls 4p transition to the triply degenerate41," molecular orbital (Apte and Mande, 1980).Hence,splittingsor broadening in the vicinity ofthe edgecrestis evidenceofbroken degeneracyin the antibonding orbitals due to
asymmetric metal-ligand bonding. The symmetry of final
statescan be probed by angularmeasurements(Hahn and
and Veblen, 1990). However, in all likelihood, bond_ Hodgson, 1983; Fr6tigny et al., 1986)using
singlecryslength variation is not large enoughto account complete- tals, but in their absence,near main-edge
spectralfeatures
ly for the threefold increase in the intensity of the are mainly interpretedqualitatively,
by comparingknown
pyrolusite spectrum relative to that of buserite. In our with unknown
structures.
opinion, it should rather be regardedas a factor that may
The main-edgespectrum of MnCO, is featureless,with
reinforce some other unelucidated effect.
a single,well-definedcrest(Fig. 4a). This edgeshapeagrees
Although we are unableto provide an explanationbased with the high symmetry of the Mn site
Qm),withthe full
on physical parametersfor the trends within the manga_ point group (Drr), and with six equivalent
Mn-O distancnate suite, we can state that peak intensity is roughly es (2.19 A;. fne main-edge spectra phyllomanganates
of
proportional to the ratio of edge-to corner-sharingMnO. are also featureless(Fig.
4b), indicating a highly symoctahedra,i.e., the larger the tunnel size (Turner and Bu_ metric Mn site. This interpretation corroborates
that deseck, 1979),the lower the peak intensity and the smaller termined from their weak preedgeintensity.
In contrast,
its width. The lowest magnitude is observed for sodium several featuresare observed on the
edgecrestsofpyrobuserite, which has no corner-sharingoctahedra (details lusite
and p-MnOOH, which, in the case of
1tel14tto*)
presentedin Manceau et al., 1992), and the highest in_ I6lMn:+ ions, can be interpreted
by the nondegeneracyof
tensity is obtained for pyrolusite, where each octahedron p orbitals as a result of
Jahn-Teller distortion. In pyroshareseight corners and two edges.Our structural inter_ lusite, p orbitals are also nondegenerate,
since the Mn
pretation is strengthenedby the fact that the trend ob_ octahedronis stretched
alongthe z axis [d(Mn-O) : 1.88
served in the phyllomanganateto tectomanganateseries A x 4; d(Mn-O): 1.90 A x 2, site
symmetrymmm;
can be reproducedby linear combinations ofbuserite and Baur, 19761.Although main-edge features
are sensitive
pyrolusite spectra (Figs. lb, 7b). Furthermore, the im_ to subtlechangesin
site geometry(Waychunas,1987);it
portance of long-range order effectson preedgefeatures is surprising that
this small variation in the Mn-O dishasa parallelin the caseof hematite(Dr?igeret al., l ggg). tances leads to such large crest
broadening. Apparently,
Thus, preedgeintensity offers a clue to local structure of a simple molecular orbital approach
is not sufficient to
unknown manganates.
describethe edgefeaturesofmanganeseoxides; it is necThe preedgespectraofhydrous manganeseoxides can essaryto consider a larger molecular
cluster that would
be divided into three groups based on their height (Fig. include nearestcation shells.
3). The first group includes samples that have a weak
Solid-state effectsin the main-edge spectra of mangapreedgepeak, such as the asbolanesfrom Saalfeld and neseoxides were
first recognizedby Belli et al. (1980).
New Caledonia and the manganesegoethite. Their spec- They interpreted spectral differences
between MnO and
tra show no evidence of vertex-sharing MnOu octahedra
B-MnO, (pyrolusite) in terms of differencesin octahedral
(Fig. 3a). The secondgroup contains D-MnO". The simi- linkages:each octahedron
shares 12 edgesin the former
larity of this spectrum with that of todorokite (Fig. 3b) oxide and two edgesand eight corners
in the latter. Of
suggeststhat d-MnO, doesnot possessa layeredstructure. particular interest is the similarity of
spectra for MnO
This interpretation is fully consistent with main-edge and the phyllomanganates:all are
characterizedby an
spectraand data from EXAFS and XRD and indicates a intense and featureless ls - 4p transition
indicating a
3-D O framework structure(Manceauet al.. 1992).The completely unfilled final p state. These
similarities in
third group comprisesnatural vernadite and birnessite. spectrareinforce the idea that in manganese
oxides nearThesespectraare ofintermediate height, rangingbetween est cation shells are important for
the final state wave
those of the two precedinggroups of samples,which sug- function, as in both of these structures
MnOu octahedra
geststhat vemadite and birnessite might have some cor_ are linked
only by edges.However, the most convincing
ner-sharing octahedra in their structure.
support for the existenceof solid-state effectsin the viMain edge. The shape and intensity of the main-edge cinity of the edgecrest comesfrom
a comparison of speccrest of tetravalent manganatesprogressivelychange in tra from TiO, (Waychunas,1987)
and MnOr. Rutile and
the seriesfrom pyrolusite-ramsdelliteto buserite(Fig. ab). pyrolusite, which are isostructural, possess
similar specSpectral features observed on the main absorption edge tra. The same is true for phyllomanganates
and anatase,
are usually interpreted using molecular orbital theory, where chains of edge-sharedTiO,
octahedra are linked
sometimes in terms of density of states,or by multiple through edgesyielding a pseudolayered
structure.
scatteringsabout the atomic cageconstituted by nearest
The edge crest increasesin intensity and is less broad
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
from tectomanganatesto phyllomanganates(Fig. 4b). On
the basis of the precedingdiscussion,this trend may also
be explained with a solid-state approach. A progressive
changein local structure is manifested by an increasein
the number of edge-sharingoctahedra at the expenseof
corner-sharing octahedra. Thus, short-range mineral
structure can be deducedfrom main-edgespectra,just as
from preedgespectra.Edge-crestspectralfeaturesprovide
information about the way octahedra are linked to each
other, so their analysis often reinforcesevidencederived
from preedgedata.
The similarity between the main-edge spectra of todorokite and D-MnO, affords an additional clue to the
structural differencebetweenbirnessiteand 6-MnO, (Fig.
4c). The MnK edgesof vernadite (Fig. ab) and birnessite
(Fig. 4c) are all similar to those of referencephyllomanganates.They have a single,well-defined,and intenseedge
crest suggestingsimilar short-range order. This finding
appearsat variance with preedgeresults,which suggested
a scarcity ofcorner-sharing octahedra in both vernadite
and birnessite. Given the evident low sensitivity of
XANES spectroscopyto short-range structure, one may
conclude that both preedge and main-edge results are
convergent,indicating that, if present,there are few MnO-Mn vertex linkages,or they are at least less abundant
than in todorokite.
Site occupationof Fe
Fe3* ions, unlike Mna+, can occupy both sixfold- and
fourfold-coordinated sites in minerals. The low crystallinity of ferric gels results in a large distribution of Fe3+
sites that have slightly different types and arrangements
ofneighboring ions. This local disorder renders classical
structural and spectroscopicmethods, such as Mossbauer
spectroscopy(Murad and Schwertmann, 1980; Cardile,
1988), essentiallyinsensitiveto the coordination environment of Fe. Fortunately, this is not a limitation for
preedgespectroscopy:it has been successfullyusedto determine the Fe sites in natural and synthetic hydrous ferric gels(Combeset al., 1989,1990;Manceauet al., 1990a).
Preedgespectraof all vernadite samplesare similar to
that of feroxyhite (Fig. 5b), whose structure is similar to
that of hematite (Patrat et al., 1983).Thus, we do not
detect fourfold-coordinated Fe in vernadite. The ability
of preedgespectroscopyto detect the presence6f tal['s:+
can be evaluatedfrom the examination of the maghemite
(7-FerO) spectrum. If we compare the full ls - 3d intensity of maghemite to a linear combination of spectra
for goethite and FePOo,a mean talFe3+concentration of
27o/ois determined (Fig. 5c). This estimate can be compared with structural data from the literature to assess
the site occupancy of Fe in an unknown oxyhydroxide.
The 7-FerO, possesses
a defect spinel structure,and there
has been some controversy over the distribution of vacancies(see,e.9.,Sinha and Sinha, 1957; Fergusonand
Hass, 1958;Annerstenand Hafner, 1973).Dependingon
the author and probably on the nature of the material
studied, the distribution of vacanciesrangesfrom a sta-
I l4l
tistical distribution over all tetrahedral and octahedral
cation sites to a position exclusively at octahedrallattice
sites. The percentageof larFemay be considered to be
which is significantly greater than
between 33 and 37010,
our experimentalvalue (27o/o).lnthe worst case,our determination of the tetrahedral content derived from the
preedgespectroscopymight be underestimated by l0o/0.
Basedon the similarity of vernadite to feroxyhite spectra
and this l0o/odetection limit, we conclude that there is
no evidence for fourfold-coordinated Fe3+ ions in vernadite.
Electronic structure of Co in asbolane
The main-edgestructure and energysuggestsixfold coordination and a trivalent state for Co in asbolane.This
interpretation agreeswith the Co-(O,OH) distancedetermined from our EXAFS data. This topic will be discussed
further after presentationof more data in the secondpart
of this work (Manceau et al., 1992).
CoNcr,usroNs
This study demonstrates the potential for XANES
spectroscopyin studies of crystal chemical properties of
Mn, Fe, and Co in minerals. Specifically,MnK preedge
spectrahave been shown to reflect changesin the valence
and coordination number of Mn atoms. Sensitivity is high
enough to allow differentiation of Mn ions with different
oxidation statesand site occupationsas, for instance,the
two oxidation statesof Mn2* and Mn3+ in MnrOo, or the
in 1-MnrOr' Suchdistinction
two Mn sites(t4rMn,t61Mn)
is not currently possible with other spectroscopictechniques, such as X-ray photoelectron spectroscopy(XPS;
Oku et al., 1975; Murray and Dillard, 1979; Dillard et
al., 1982; Crowther et al., 1983; Murray et al., 1985),
energy electron loss spectroscopy (EELS; Rask et al.,
1987), and UV-visible reflectancespectroscopy(Strobel
et al., 1987). Preedgespectrahave also been shown to be
sensitive to the local structure of tetravalent manganese
oxides becausethe intensity MnOr spectra depends on
the ratio of edge-to corner-sharing MnOu octahedra. Thus
MnK XANES spectroscopyservesas a structural tool to
complement other techniques for studying short-range
structure of highly disordered manganeseoxides.
The analysisofvarious hydrous oxides has shown that
Mn is essentiallytetravalent even in natural Mn-bearing
goethite. The detection limit of low-valence Mn ions is
estimated to be about 20o/o.ln hydrous manganeseoxides, Fe and Co are both trivalent and octahedrally coordinated. The detection limit of talFe3*by FeK preedge
spectroscopyis about 100/0.The preedgeand main-edge
spectraof 6-MnO, are similar to those of todorokite, indicating that the two structures have a similar ratio of
edge- over corner-sharingoctahedra. Our evidence contradicts the generally accepted belief that d-MnO, possessesa layered, birnessiteJike structure. Additional proof
of the distinct structure of 6-MnO, and birnessitewill be
provided through EXAFS and XRD data presented in
the secondpart of this work (Manceau et al., 1992).
lt42
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
AcxNowlnocMENTS
The authors thank R. Giovanoli for providing the synthetic birnessite
sample, D. Bish for providing several hollandite, psilomelane,and todorokite samples,and the staffof the LURE synchrotron radiation facility A critical reading of a preliminary version by G.A. Waychunas is
acknowledged. Iast, and not least, the authors express their gratitude to
Susan Stipp, who improved the English. This research was supported by
CNRS/INSU through the DBT program,gant 90 DBT 1.03(contribution
no.4l3)
RnrrnnNcns cITED
Annersten, H., and Hafner, S.S.(1973) Vacancydistribution in synthetic
spinelsofthe seriesFe,Oo-"yFe,O..
Zeitschrift fiir Kristallogaphie, I 37,
321-340.
Apte, M.Y., and Mande, C. (1980) The shapeand extendedfine structure
ofthe manganeseK X-ray absorption discontinuity in its oxides.Journal of Physicsand Chemistry of Solids, 41, 3O7-3 12.
-(1982)
Chemical effects on the main peak in the K absorption
spectrum of manganesein some compounds. Journal of Physics C:
Solid State Physics, 15, 607-613.
Arnold, H. (1986) Crystal structure of FePO
294 and 20 K. Zeitschrift
"at
fiir Kristallographie, 177, 139-142.
Baur, W.H. (1976) Rutile+ype compounds.V. Refinementsof MnO, and
MgF,. Acta Crystallographica,B32, 2200-2204.
Belli, M., Scafati,A., Bianconi, A., Mobilio, S., Palladino, L., Reale,A.,
and Burattini, E. (1980) X-ray absorption near edgestructures (XANES)
in simple and complex Mn compounds. Solid State Communications,
3 5 , 3 5 5 - 3 61 .
Blake, R.L., Hessevick,R.E., Zoltai, T., and Finger, L.W. (1966) Refinement of the hematite structure. American Mineralogist, 51,123-129.
Bricker, O. (1965) Some stability relations in the system Mn-O1HrO at
25'and one atmosphere total pressure.American Mineralogist, 50,
1296-1354.
Brouder, C. (1990) Angular dependenceof X-ray absorption spectra.
Journal of Physicsand CondensedMatter, 2, 701-738.
Brown, G.8., Jr., C-alas,G., Waychunas,G.A., and Petiau,J. (1988) X-ray
absorption spectroscopy:Applications in mineralogyand geochemistry.
In Mineralogical Societyof America Reviews in Mineralogy, 18, 431512.
Bystrdm, A., and Bystriim, A.M. (1950) The crystal structure of hollandite, the related manganeseoxide minerals, and cMnO,. Acta Crystallographica,3, 146-154.
Bystrrim, A.M. (1949) The crystal structureof ramsdellite,an orthorhombic modification of MnO,. Acta Chemica Scandinavica,3, 163-173.
C-alas,G., and Petiau, J. (1983) Coordination of iron in oxide glasses
through high resolution K-edge spectra: Information from the pre-edge.
Solid State Communications. 48. 625-629.
Cardile, C.M. (1988) Tetrahedral Fe3* in ferrihydrite: 5'Fe Mdssbauer
spectroscopicevidence.Clays and Clay Minerals, 36,537-539.
Chukhrov, F.V., Gorshkov, A.I., Rudnitskaya, E.S., and Sivtsov, A.V.
(1978a) Birnessite characterization. Izvestia Akademie Nauk, SSSR,
Seriya Geologicheskaya,9, 67-7 6.
Chukhrov, F.V., Gorshkov, A.I., and Rudnitskaya, E.S. (1978b) On vernadite. Izyestia Akademie Nauk, SSSR,Seriya Geologicheskaya,6,519.
Chukhrov, F.V., Gorshkov, A.I., Drits, V.A., and Sivzev, A.V. (1982a)
New structural varieties of asbolane.Izvestia Akademie Nauk. SSSR.
Seriya Geologicheskaya, 6, 69-7 7.
Chukhrov, F.V., Gorshkov, A.I., Sivtsov, A.V., Dikov, yu.p., and Berezovskaya,V.V. (1982b)A natural analogof e-MnOr. Izvestia Akademie
Nauk, SSSR,Seriya Geologicheskaya,56-65. (Translation in Intemational GeologyReview, 1983,708-718.)
Chukhrov, F.V., Drits, V.A., Gorshkov, A.I., Sakharov,B.A., and Dikov,
Y P. (1987) Structural models ofvernadites. Izvestia Academie Nauk,
SSSR,Seriya Geologicheskaya,12, t98-204.
Chukhrov, F.V., Manceau, A., Sakharov, B.A., Combes, J.-M., Gorshkov, A.I., Salyn, A.L., and Drits, V.A. (1988) Crystal chemistry of
oceanicFe-vernadites.MineralogicheskiiZhurnal, | 0, 7 8-9 Z.
Combes, J.-M., Manceau, A., Calas, G., and Bottero, J.-Y. (1989) Formation offerric oxides from aqueoussolutions:A polyhedralapproach
by X-ray absorptionspectroscopy.I. Hydrolysis and formation offerric
gels.Geochimica et Cosmochimica Acta, 53, 583-594.
Combes, J.-M., Manceau, A., and Calas, G (1990) Formation of ferric
oxides from aqueoussolutions: A polyhedral approach by X-ray absorption spectroscopy.II. Hematite formation from ferric gels. Geochimica et CosmochimicaActa. 54. 1083-1091
Crowther, D.L., Dillard, J.G., and Murray, J.W. (1983) The mechanism
of Co(II) oxidation on synthetic birnessite.Geochimica et Cosmochimica Acta. 47. 1399-1403.
Decarreau,A. (1985) Partitioning ofdivalent transition elementsbetween
octahedral sheetsoftrioctahedral smectitesand water. Geochimica et
Cosmochimica Acta- 49. 1537-1544.
Decarreau, A., Grauby, O., and Petit, S. (1992) The actual nature of
octahedralsolid solutions in clay minerals: Resultsfrom clay synthesis.
Applied Clay Science,in press.
Delaplane,R.G., Ibers, J., Ferraro, J.R., and Rush, J.J. (1969) Diffraction
and spectroscopicstudies of the cobaltic acid system HCoO,-DCoO,.
JournalofChemical Physics,50, 1920-1927.
Deliens, M., and Goethals, H. (1973) Polytypism of heterogenite.MinerafogicalMagazine, 39, 152-157.
Dillard, J.G., Crowther, D.L., and Murray, J.W. (1982) The oxidation
states of cobalt and selected metals in Pacific ferromanganesenodules.
Geochimica et Cosmochimica Actc, 46,755-759.
Driiger, G., Frahm, R., Materlik, G., and Briimmer, O. (1988) On the
multipole character ofthe X-ray transitions in the pre-edgestructure
ofFe K absorption spectra.PhysicaStatus Solidi B, 146,287-294.
Drits, V.A. (1987) Electron diffraction and high-resolution electron microscopyof mineral structures.Springer-Verlag,Berlin.
Ebinger,M.H., and Schulze,D.G (1989)Mn-substituted goethiteand Fesubstituted goutite synthesized at acid pH. Clays and Clay Minerals,
37, t5t-156.
Effenberger,H., Mereiter, K., and Zemann, J. (1981) Crystal structure
refrnementsof magnesite,calcite, rhodochrosite, siderite, smithonite,
and dolomite, with discussionof some aspectsof the stereochemistry
of calcite type carbonates.Zeitschrift fiir Kristallographie, 156, 233243
Eggleton, R.A., and Fitzpatrick, R.W. (1988) New data and a revised
structural model for ferrihydrite. Clays and Clay Minerals, 36, lll-
r24.
Ewing, F.J. (1935) The crystal structureof lepidocrocite,T-FeOOH. Journal ofChemical Physics,3, 420-427.
Ferguson,G.A., Jr., and Hass, M. (1958) Magnetic structureand vacancy
distribution in 7-Fe,O, by neutron diffraction. Physical Review, ll2,
ll30-ll3r.
Fr6tigny, C., Bonnin, D., and Cortes, R. (1986) Polarization effects in
XANES of layeredmaterials:Alkali-graphite intercalation compounds
study. Journal de Physique, C8, 47,869-873.
Giovanoli, R. (1980a) On natural and synthetic manganesenodules. In
I.M. Varentsov and G. Grasselly, Eds., Geology and geochemistryof
manganese,vol. l, p. 159-202. Schweizerbart'scheVerlagsbuchhandlung, Stuttgart.
-(1980b)
Vemadite is random-stackedbirnessite.Mineralium Deposira,15,251-253.
-(19E5)
A review of the todorokite-buseriteproblem: Implications
to the mineralogyof marine manganesenodules:Discussion.American
Mineralogist, 7O, 2O2-2O4.
Giovanoli, R., And Stiihli, E. (1970) Oxide und Oxidhydroxide des dreiund vierwertigen Mangans. Chimia,24, 49-61.
Giovanoli, R., Stiihli, E., and Feitknecht, W. (1969) Uber Struktur und
Reaktivit.:it von Mangan (IV) Oxiden. Chimia, 23, 264-266.
-(1970a)
Uber Oxyhydroxide des vierwertigen Mangans mit
Schichtengitter,1. Natrium Mangan (II, Ill)-Manganat (IV). Helvetica
Chimica Acta. 53. 209-220.
-(1970b)
Uber Oxidhydroxide des vierwertigen Mangans mit
Schichtengitter. 2. Mangan Qll)-Manganat (IV). Helvetica Chimica Acta,
53,453-464.
Hiigg, G. (1935)Die Kristallstruktur des magnetischenFerrioxids,7-FerOr.
Zeitschrift liir physikalischeChemie, 829, 95-103.
MANCEAU ET AL.: MANGANESE HYDROUS OXIDES I
Hahn, J.E., and Hodgson, K.O. (1983) Polarized X-ray absorption spectroscopy. In M.H. Chisholm, Ed., Inorganics chemistry: Towards the
2lst century ACS SymposiumSeries,2l l, 431-444.
Harrison, P.M., Fischbach, F.A., Hoy, T.G., and Haggis, G.M (1967)
Ferric oxyhydroxide core of ferritin. Nature, 2 I 6, I I 88- I 190.
Hill, R.J., Craig, J.R., and Gibbs, G.Y. (1979) Systematicsof the spinel
structure type. Physicsand Chemistry of Minerals, 4, 317-339
Kutzler, F.W., Natoli, C.R., Misemer, D.K., Doniach, S., and Hodgson,
K.O. (1980) Use ofone-electron theory for the interpretation ofnear
edge structure in K-shell X-ray absorption spectraoftransition metal
compfexes.Journal of Chernical Physics,73, 3274-3288.
L1.tle,F.W., Greegor,R. B , and Panson,A.J. (1988) Discussionof X-ray
absorption near edgestructure:Application to Cu in high T. superconductors, LarsSr,CuOo and YBarCu,O,. Physical Review, B37, 15501562.
Manceau, A., and Combes,J.-M. (1988) Structure of Mn and Fe oxides
and oxyhydroxides: A topological approach by EXAFS. Physics and
Chemistry of Minerals, l5(3), 283-295.
Manceau,A., Llorca, S., and Calas,G. (1987) Crystal chemistry of cobalt
and nickel in lithiophorite and asbolanefrom New Caledonia. Geochimica et CosmochimicaActa. 5 l. 105- I 13.
Manceau, A., Combes, J.-M., and Calas, G. (1990a) New data and a
revised model for ferrihydrite: A comment on a paperby R.A. Eggleton
and R.W. Fitzpatrick. Clays and Clay Minerals, 38, 331-334.
Manceau, A., Sanz,J., Stone, W.E 8., and Bonnin, D. (1990b) Distribution of Fe in the octahedral sheetof trioctahedral micas by polarized
EXAFS. Comparison with NMR results. Physics and Chemistry of
Minerals, l7, 363-370.
Manceau, A., Gorshkov, A.L, and Drits, V. (1992) Structural chemistry
of Mn, Fe, Co, and Ni in manganesehydrous oxides: Part II. Information from EXAFS spectroscopyand electron and X-ray diffraction.
American Mineralogist, 77, 1144-1157.
Miura, H. (1986) The crystal structure of hollandite. Mineralogical Journ a l . 1 3 .l l 9 - 1 2 9 .
Murad, E., and Schwertmann, U. (1980) The Mtissbauer spectrum of
ferrihydrite and its relations to those of other iron oxides. American
Mineralogist, 65, lO44-1O49.
Munay, J.W., and Dillard, J.G. (1979) The oxidation of cobalt(Il) adsorbedon manganesedioxide. Geochimica et CosmochimicaActa, 43,
781-787.
Murray, J.W., Balistrieri, L. S., and Paul, B. (1984) The oxidation state
of manganesein marine sedimentsand ferromanganesenodules.Geochimica et CosmochimicaActa. 48. 1237-1247.
Murray, J.W., Dillard, J.G., Giovanoli, R., Moers, H., and Stumm, W.
(1985) Oxidation of Mn(II): Initial mineralogy, oxidation state and
ageing.Geochimica et CosmochimicaActa, 49,463-470.
Oku, M., Hirokawa, K., and lkeda, S. (1975) X-ray photoelectron spectroscopy of manganese-oxygen
systems.Journal of Electron Spectroscopy and Related Phenomena,7, 465-473.
Patrat, G., De Bergevin,F,. Perret, M., and Joubert, J C (1983) Structure
locale de d FeOOH. Acta Crystallogaphica, B39, 165-170.
Pauling, L., and Kamb, B. (1982) The crystal structure of lithiophorite.
American Mineralogist, 67, 8 17-821.
Petiau, J., Calas, G., and Sainctavit, P. (1987) Recent developmentsin
the experimentalstudiesofXANES. Joumal de Physique,C9, 48, 1085l 096.
Post, J.E., and Appleman, D.E. (1988) Chalcophanite,ZnMn,O, 3HrO:
New crystal-structure determination. American Mineralogist, 73, l4O1t 404.
Post, J.E., and Bish, D.L. (1988) Rierveld refinement of the todorokite
structure. American Mineralogist, 73, 86 | -869
Post, J.E., and Veblen, D.R (1990) Crystal structure determinations of
synthetic sodium, magnesium, and poEssium birnessite using TEM
and the Rietveld method. American Mineralogist, 75,477-489.
Post, J E., Dreele, R B., and Buseck,P.R. (1982) Symmetry and cation
displacementsin hollandites:Structurerefinementsof hollandite, cryptomelane and priderite. Acta Crystallographica,B38, 1056-1065.
It43
Poumellec, B., Cortes, R., Tourillon, G., and Berthon, J. (1991) Agular
dependenceofthe Ti K edge in rutile TiO,. Physica Status Solidi B,
r64,319-326.
Rask, J.H., Miner, B.A., and Buseck,P.R. (1987) Determination of manganeseoxidation in solids by electron energyJossspectroscopy.Ultramicroscopy,2 l. 32 | -326.
Sainctavit, P., Petiau, J., Manceau, A., Rivallant, R., Belakhovsky, M.,
and Renaud, G. (1988) A two-mirror device for higher harmonic rejection. Nuclear Instruments Methods, 273, 423-428.
Shterenberg,L.E., Aleksandrova, V.A., and Sivtsov, A.V. (1985) Composition, structure and peculiarities in the distribution of Fe, Mn-micronodules in the sediments of the north-eastern Pacific. Litologiya i
PoleznyeIskopayemye,6, 58-70.
Sinha, K.P., and Sinha, A.P.B. (1957) Vacancy distribution and bonding
in some oxides of spinel structure.Joumal of Physical Chemistry, 61,
7 58-761.
Stiers, W., and Schwertmann,U. (1985) Evidence for manganesesubstitution in synthetic goethite. Geochimica et Cosmochimica Acta, 49,
1909-l9ll.
Strobel, P., Charenton,J.C., and Irnglet, M. (1987) Structural chemistry
of phyllomanganates:Experimental evidence and structural models.
Revue de Chimie Min6rale, 24, 199-220.
Szytula, A., Burewicz,A., Dimitrijevic,2., Krasnicki, S., Rzany, H., Todorovic, J., Wanic, A., and Wolski, W. (1968)Neutron diffraction studies ofa-FeOOH. Physica StatusSolidi, 26, 429-434.
Szytula,A , Balanda,M., and Dimitrijevic, A. (1970) Neutron difraction
studiesof B-FeOOH PhysicaStatus Solidi, 3, 1033- 1037.
Tamada, O., and Yamamoto, N. (1986) The crystal structure of a new
manganesedioxide (Rbo',MnOr) with a giant tunnel. Mineralogical
Journal, 13, 130- 140
Taylor, J.B., and Heiding, R.D. (1958) Arsenatesof the transition metals.
The arsenatesofcobalt and nickel. CanadianJournal ofchemistry, 36'
597-606.
Towe, K.M., and Bradley, W.F. (1967) Mineralogical constitution of colloidal "hydrous ferric oxides." Joumal ofColloid and InterfaceScience,
24,384-392
Turner, S., and Buseck, P.R. (1979) Manganeseoxide tunnel structures
and their intergrowths. Science,203, 456-458.
Turner, S., and Post, J.E. (1988) Refinement ofthe substructureand superstructureof romanechite American Mineralogist, 73, ll55-ll6l.
Varentsov,I.M., Drits, V.A., Gorhkov, A.I., Sivtsov, A.V., and Sakharov,
B.A. (1989) Processesof formation of (Mn,Fe)-crustsin the Atlantic:
Mineralogy, geochemistryof basic and trace elements,Krylov Underwater Mountain. In V.N. Kholodov, Ed., Sediment genesisand fundamental problems in lithology, p. 58-78. Nauka, Moscow.
Verwey, E.J.W. (1935) The crystal structureof "y-FerO,and ?-Al'Or. Zeitschrift fiir Kristallographie, 91, 65-69.
Vicat, J., Franchon,E., Strobel,P., and Tran Qui, D' (1986)The structure
of K, r,MnuO,uand cation ordering in hollandite-type structures.Acta
Crystallographica,842, 162-167.
Wadsley, A.D. (1952) The structure of lithiophorite, (Al,Li)MnO'(OH),.
Acta Crystallo$aphica, 5, 676-680.
-(1953)
The crystalstructureof psilomelane,@a,HrO)rMn,O,o.Acta
Crystallographica,6, 433- 438.
Waychunas,G.A. (1987) Synchrotron radiation XANES spectroscopyof
Ti in minerals: Effects of Ti bonding distances,Ti valence, and site
geometry on absorption edgestructure. American Mineralogist, 72, 89l0l.
Waychunas,G.A., Brown, G.E., Jr., and Apted, M J. (1983) X-ray K-edge
absorption spectra of Fe minerals and model compounds: Near edge
structure. Physicsand Chemistry of Minerals, 10, l-9.
Wong, J., Lytle, F.W., Messmer,R.P., and Maylotte, D.H' (1984) K-edge
absorption spectraofselectedvanadium compounds.PhysicalReview'
830, 5596-5609.
Aucusr 15, 1990
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Mexuscrurr AcCEPTED
Jur-v 6, 1992