THE AMDRICAN MINERALOGIST,
VOL. 56, SEP'IEMBER-OCTOBER,
1971
CRYSTAL CHEMISTRY OF THE BASIC
MANGANESE ARSENATES:
V. MIXED MANGANESE COORDINATIONIN THE
ATOMIC ARRANGEMENT OF ARSENOCLASITE
Paur-B. MoonB aNl JoANNMorrx-Case, DepartmentoJthe
of Chicago,
The Uni,uersity
Sci,ences,
Geophysical
Chicago,Illino'is,60637.
Arsrnec'r
A r s e n o c l a s i t e , M n r ( O H ) r ( A s O ) 2 , a 1 8 . 2 9 ( 2 ) , b 5 . 7 5 ( 1 ) , c 9 .Q
3 1) L , Z : 4 , s p a c e g r o u p
P2t2rZr,isbasedon"double"hexagonalclose-packed(...ch...)oxygenanionswhose
layers are normal to the c-axis. Its structure was deciphered from direct methods, and
R(hkl):0.07 for 1800 independent reflections.
The cationic occupancies are very complicated. Three non-equivalent octahedra,
Mn(2)-O, Mn(3)-O and Mn( )-O, link by edge-sharing to form walls alternately one- and
two-octahedra wide which run parallel to the 6-axis. Also running parallel to this axis are
chains of corner-sharing Mn(l)-O trigonal bipyramids which further link by corner-sharing
to As(2)-O tetrahedra forming three-membered rings; and chains of cornerlinked As(l)-O
and Mn(S)-O tetrahedra.
The interatomic Me-O averages are Mn(1)v-O 2.19, Mn(2)vLQ 2.25,Mn13)vr-O 2.22,
Mn( )vt-g 2.19, Mn(S)w-O 2.13, As(l)w-O 1.67 and As(2)rv-O 1.69 A. Althoush the
Mn(S)Iv-O polyhedron is of distorted tetrahedral shape, the Mn(5) cation resides nearly in
the plane oI the base and the polyhedron is more properly a trigonal pyramid.
INrnooucrtoN
Systematic structural investigations on members of the series
Mn2+"(OH)2"-:,(AsOa)3-,by Moore (1967a, 1967b,1968a,1968b,1970a)
shall lead to novel insights concerning the interaction between crystalchemical homology and paragenesis.We report studies on the atomic
arrangement of yet another member, arsenoclasite.
Arsenoclasite, Mn6(OHr)(AsO+)2, was first described by Aminoff
(1931)as a new speciesfrom the famous Lingban mines,in the province
of Vdrmland, Sweden. It occurs in the paragenesisadelite-sarkinitearsenoclasitein calcite-filled fissures cutting hausmannite impregnated
dolomitic marble from the "Irland" drift. Both arsenoclasiteand sarkinite crystallized later than adelite but it is difficult to decipher the relative positions in time for the first two species. Flink (192a) discussed
the occurrencesof sarkinite at Lingban and noted some specimenswith
the characteristic flesh-red color of sarkinite but with one perfect cleavage. As shown by Aminoff, "sarkinites" with perfect cleavageproved to
be arsenoclasite.Moore (I967b) re-investigated type arsenoclasite,confirmed the crystal .cell data of Aminoff, and established the uniquely
determined space group P 2Qrh. This present investigation was performed on the same crvstal used in that studv.
1539
1540
MOORE AND MOLIN-CASE
ExpBnrurNrlr,
Crystal cell parametersare presentedin Table 1, citing the paper of Moore (1967b)
which also includesindexed powder data. A crystal of 0.0003mms volume was selected
for three-dimensionalstructure analysisutilizing a PAILRED difiractometerand graphite
"monochromatized"MoK" radiation. With r as the rotation axis, 4800reflectionsincluding tlre s1'rnmetryequivalentpairs l(hhl) and l(ilkl) from the l:0- to 12-levelswere obtained using a2.2o halL-anglescanand a backgroundcounting time on both sidesof each
peak oI 20 seconds.
At first, the individual reflectionswere processedto obtain raw F(oDs)data. Since
p:137 cm-r, polyhedral transmissioncorrectionwas applied using a local version of tle
GNABS program (Burnham, 1963)and symmetry equivalent reflectionswere averaged.
Remainingwere 1800independentreflectionsabovebackgrounderror and 620independent
reflectionsof."zero" intensity. Qnly the Don-zerodata were used in tlre following study.
Sor,urron oF rrrE Srnucrunp
Solution of the arsenoclasite atomic arrangement was a miserable
problem. At first, attempts were made to decipher the structure on the
basis of a structural relationship with pseudomalachitebut several trials
of heavy atom refi.nementfailed. One key to the solution of the structure
was the subsequent assumption that arsenoclasiteis based on oxygen
close-packing, a typical feature among the known basic manganese
arsenate structures. Accordingly, the assumed structural relationship
TABLE I.
CRLSTAL CELL DATA FOR ARSENOCTASTTE,
COR}IWALLITEAND PSEI'DOI\AIACHITE.
Arsenoclasite
e (8)
E (8)
s (8)
p
space group
z
fomla
reference
IAninoff(I93I)
1 8 . 2 s( 2 )
17.61
s.7s(r)
s.8I
1snlffi3)
PBildomlachite
17.06
5.76
e . 3 1( 2 )
+.60
9oo
9zor5'
9roo2'
P21212r
PZy/a
P2y'a
4
2
2
!er5(oI0 q (Aso+)
z
cu, (olD u (Aso4),
4.161
O cbe
p carc
Cowallite
l{.49
cu, (olD q(Poq) 2
4.30-rl .35
4.21
1r.68
l{oore (1967b)
Berry(19sI)
{.3I1
Berry (I950)
COORDINATION IN ARSENOCLASIT E
1541
with pseudomalachitehad to be abandoned.The relationship a/6-b/1/3
-3.24 suggested that the a-axis is the sum of six Mn2+-O octahedral
edges,and the relationship with D automatically defines the orientation
of the octahedral voids. Furthermore, cf 4-2.34, the typical oxide layer
separation in close-packedstructures. Tests of several electrostatically
plausible heavy atom models were undertaken, but all failed.
It was then decided to attempt solution by direct methods using a
tangent routine adapted for non-centrosymmetric crystals, as described
by Dewar (1970). Normalized structure factors were calculated from
the observedstructure magnitudes applying a scalefactor and an overall
isotropic temperature factor obtained by the method of Wilson (1942).
The four two-dimensional reflections initially chosento select the origin
and the enantiomorph led to a meaningless solution. On the second
attempt, the reflections(160), (041), (671), (144), and (511) were assigned the values rf 2, 0, r, y, and. z respectively. Symbolic addition
applied to these reflections with the program MAGIC (Dewar, 1970)
yielded 118 additional phaseswith a variance <0.65 and indicated that
and'
r-z:r/2,
and r: -rf4
or 3r/4. Setting *:3r/4
!:-zr/2,
z:zr/4 satisfied the criterion for origin and enantiomorph selection.
The 123 phasesfrom MAGIC were submitted to tangent formula refinement. After two cycles, a total ol 263 reflections were determined with
E>1.3 and the phase shifts indicated reasonable convergence. An
.E-map calculated from these reflections appears in Figure 1 with location of the final heavy metal positions superimposed.
It is apparent that the .B-map contained the sufficient heavy atom
information for successfulatomic parameter location and convergence
through Fourier synthesis. The correct ascription of the initial atomic
positions and species was facilitated by the previous assumption of
oxygen close-packing. Approximate metal-metal distances which were
compatible with sensiblecrystal chemistry expectedfor a basic manganese arsenate combined with relative peak heights led to peaks A, B,
C, D, E, F:As(1), As(2), Mn(5), Mn(4), Mn(2) and Mn(3) respectively
(Fig. 1). The reliability index,
R(hkt) :
>lln1oasl
| - | n1r'tr1ll
: 0.39
> | nloa'yI
for this arrangement. A Fourier synthesis of the phases calculated
revealed the Mn(1) atom which correspondsto the feeble peak labelle{
('G"
in Figure 1. Further Fourier syntheses followed by parameter
refinement for the metals led,to R(hhl):0.20. At this stage, eight nonequivalent oxygen atoms were located on the Fourier map and a double
r542
MOORI' AND MOLIN-CASE
+
M n( 4 )
+0.38
Mn(5)
+0.40
M n( 3 )
+0.07
Mn(l)
+0.27
C
Fro. 1. Projection of the three-dimensional .E-map dorvn the b-axis resulting from the
direct determination of 263 symmetry independent phase angles. The approximate I
coordinates obtained from the three-dimensional map as well as the final heavy metals and
their positions refined by least-squares are included.
hexagonal close-packed motif became apparent. The remaining four
atoms were approximatelv located by interatomic distancecalculation5.
Typical for a close-packedslructure, some of the Iight atoms had to be
"coaxed" along even at the stage of the relatively low reliability index
inentionedabove.
RnntNrvorqt
The arsenoclasiteasymmetric formula unit constitutesone molecular
unit of HaMn5As2O1z.
Atomic coordinates of the five manganese, two
arsenic and twelve oxygen atoms were refined using a local version of
the familiar ORFLS least-squares
program of Busing, Martin and Levy
(1962) for the IBM 7094 computer. Finally, scale factor, atomic coordinate and isotropic thermal vibration parameterswere refined on the
basis of full-matrix inversion until the parameter shifts were within their
limits of error. The final reliabilitv index was R(hhl\:0.070 for 1800
COORDLNATIONIN A RSENOCLASITE
TABLE 2.
I J4.t
ARSENOCIASITE: ATOMIC COORDINATES, CATIoN CO0RDIMTI0N
NUMBERS
AND I SOTROPIC THERI'IAL V] BRATION PARAMETERS.
Gsl]Iateq
standard
eryors
parentheses)
in
.
x
v
Z
s (82)
Mn(1) V
0 " 4 3 2 3( 1 )
0 . 2 6 e 7( s )
o . 75 2 2( 3 )
0.6s(3)
I"lI'(2) VI
. 0 3 0 3( r )
. o s 4 ' l( 5 )
. 8 8 8 6( 3 )
.6r (3)
wr(3) vI
.22r4(t)
. o 7L 2 ( 5 )
" 8 s 8 2( 3 )
.se(3)
Mn(r+) VI
.124r(2)
" s s 8 7( s )
. 8 7 e 6( 3 )
. 7 6( 3 )
Mn(s) IV
. 3 1 6 ' r( 2 )
(5)
.s80r+
. 0 0 0 e( 3 )
. 7r (3)
As(I) IV
. 3 7 r + r(+r )
.llr7 (3)
.07rs(2)
.08(2)
As(2) IV
_ 1 2 4 3( 1 )
. 1 92 8( 3 )
. 1 8 3 8( 2 )
. 0 1( 2 )
o (1) = (ol0
.0sre(7)
. 7 3 s 0( 2 6 )
.021s(r.6)
. e 8( 2 r )
0(2) = (0D-
.202s(7)
. 3 8 4 4( 2 6 )
. 7 3 e 7( 1 6 )
.e6(18)
o(3) = (oD-
. 0 ' + r 2( 7 )
.3676(2s)
. 7 s 6 9( 1 6 )
. e 0( 1 7 )
o(4) = (oD-
-
"2L7L(7)
.746r(2s)
" 0 2 8 2( f s )
.e0(17)
o (s)
.f46r (6)
trtrtr]r"?)
. 2 6 4 3( 1 s )
.62(r6)
0 (6)
.I27s (e)
o (7)
.L762(7)
o (8)
o (e)
.232+(2+)
" 0 0 r 2( 1 7 )
r . 04 ( r 8 )
- . 0 2 7 7G q )
. 2 3 3 2( L 6 )
. 8 7( f 6 )
" 0 3 8 0( 7 )
. 0 e 8 0( 2 6 )
.2282 (16)
1 . 0 0( 1 9 )
. 3 7 s s( 8 )
.rr03 (23)
" 2 s 0 8( r s )
. e s( r 7 )
. 6 e( 1 7 )
o (10)
.2S3r+(7)
.2L87 (24)
. 0 2 0 6( r - s )
o (rr)
. + 3 t + 2( 7 )
. 3 0 0 7( 2 4 )
- .000q(16)
.87(re)
o( r 2 )
. 3 e 1 6( 7 )
. 8 4 r + (82 s )
.0lss (16)
r.o7(17)
reflections,constituting a data to variable parameterratio of about 25: 1.
Final atomic and isotropic thermal vibration parametersare listed in
Table 2. The oxygen thermal vibration parameters range from 0.6 to
l.l 1^2,typical values for oxygen close-packing.The Mn2+ parameters
range from 0.6 to 0.8 and As5+from 0.0 to 0.1 Ar. The lf (aDs)| - p(catc)
data appear in Table 3.1
r ro obtain a copy of rable 3, order
NApS Document No. 01521 from National Auxiliary Publications Service of the A.s.I.s., c/o ccM rnformation corporation, 909 Thirrl
Avenue, New York, New York, 10022; remitting $3.00 for microfiche or g5.00 for photocopies, payable in adva,nce to CCMIC-NApS.
1544
MOORE AND MOLIN-CASE
DrscussroN oF TrrE Srnucruns
Arsenoclasite has been generally regarded as structurally related to
pseudomalachite,Cu6(OH)4(PO4),and cornwallite, Cu6(OHr)(AsO+)2,
and their crystal cell relationships are summarized in Table 1. Palache,
Berman, and Frondel (1951) classify arsenoclasitewith pseudomalachite
and Strunz (1970) places all three compounds together and suggeststhat
arsenoclasitemay possibly be derived from the others on the basis of
unit cell twinning.
Despite the marked similarity in compositions and crystal cells,
arsenoclasiteis not closely related structurally to the other compounds
except for the presenceof the same kind of octahedral wall revealed in
the structure of pseudomalachite investigated by Ghose (1963). Pseudomalachite is based on sheets of distorted Cu2+-O octahedral arsenoclasite is based on walls and chains of three distinct coordination polyhedra: Mnvr-O octahedra, MnY-O trigonal bipyramids and Milv-O
tetrahedra (trigonal pyramids).
Arsenoclasite is constructed of a "double" hexagonal closepacked array ol oxygen atoms whose layers are stacked perpendicular to the c-axis. It shares this f eature in common with
flinkite, ry[1r+rffn3+(OH)n(AsOu);allactite, Mnz(OH)s(AsOr)z; and
synadelphite, Mne(OH)e(HzO)r(AsOa)(AsOr)zand we conclude that
the oxygen stacking sequence( ' ' ' .h ' ' ') i. one of the more persistent underlying aSpectsof the basic manganesearsenate crystal chemistry. Figure 2 illustrates the population sequence along the c-axis'
Oxygen atoms are situated at z-0, +, +, Z.The trigonal bipyramidally
coordinated Mn(1) cations are located at z-i and {. The octahedrally
coordinated cations, Mn(2), Mn(3) and Mn(4) are distributed at z-*,
are
3,8, +.The tetrahedrally coordinated cations As(1) and Mn(S),
As(2)
j
coordinated
and
tetrahedrally
a-0,
located above and below
above and below z-1, *. The crystallochemical formula can be written
MnTYIMnYMnIY(OH)r(AsrvOr)zithus, I of the available octahedral voids
are occupied. The trigonal bypyramid is constituted of two tetrahedral
voids joined by face-sharing with Mn(1) at the center of the shared
face. Consequently, z% of the available tetrahedral voids are utilized by
cations.
It is instructive to examine the oxygen packing density in the arsenoclasite structure. All close-packedlayers are fully o-ccupiedwith respect
to anions and the volume per oxygen atom is 20.4L3. This value can be
compared with cubic close-packed manganosite, MnO, which has a
volume of 21.8At, the major oxygen volume difference between the two
doubtlessly arising from the more tightly bound As5+-O tetrahedra in
arsenoclasite.
COORD]N ATION I N ARSENOCLASITE
1545
o
9.2A
7/B
3rq 6.9A
h
AsM
5te
trz 4.6i
c
,8
,/^
o
2.3A
h
tte
9-
0-,
z=O 0'OA c
Frc. 2. rdealization of the population sequence of cations and their coordination
numbers and anions along the z-direction in arsenoclasite. Heights are given as lractional
and absolute coordinates with respect to the c-axis. The letters ((c" and ,.h', refer to the
centers of the cubic and hexagonal close-packed blocks respectively.
1546
MOOREAND MOLIN-CASE
To describe thoroughly the very complex yet aesthetically pleasing
arsenoclasitestructure requires careful dissection.The Mn(2)-, Mn(3)and Mn(4)-oxygen octahedra join by edge-sharingto form a wall of
octahedra,alternately one- and two-cctahedrawide which runs parallel
to the 6-axisand which is oriented parallel to [001]' This wall defines
the D:5.754 repeat and is the compcnent also commcn to the pseudomalachite structure. It is featured in Figure 3a' Ghose (1964) has com'
mented on the occurrenceof this wall in other first transition series
oxysalt structures as well, including its presence in hydrozincite,
the latter structure
Zns(OH)e(COs)2,and lindgrenite, Cus(OH)r(MoOa)2,
determined by Calvert and Barnes (1957). It is also the component in
crystal structure,as discussedby Moore (1970b)'
the kotoite, Mge(BOa)2,
Projected down the 6-axis, the walls are stacked like brickwork as a
result of the two-fold screw operations (Fig. 4) and possessno obvious
stacking relationship to pseudomalachite.
The Mn(l)-O trigonal bipyramids link along two corners to form
infinite chains which also run parallel tc the D-axis.One of these corners
also joins to the As(2)-O tetrahedron forming chains of Mn(1)-As(2)Mn(1) three-memberedrings (Figure 3b). This composite chain links
through vertices at a common level along z by corner-sharingto the
octahedral wall.
A third type of chain, also running parallel to the b-axis,is present
in arsenoclasiteand consistsof corner-sharingMn(5)-As(1) tetrahedra
(Figure 3c). This chain links laterally to an octahedral wall on either
s i d e a n d t h r o u g h i t s a p i c a l o x ) ' g e na t o m s t o a n o t h e rs y m m e t r y e q u i v a Ient octahedral wall. The tetrahedral vertex, O(11), is also joined to
verticesof the Mn(1)-O trigonal bipyramids.
Assembled,the arsenoclasitestructure is shown idealizedin Figure 5.
It is remarkable in possessingthree distinct Mn-O coordination polyhedra and it is gratifying that direct methods succeededin unravelling
an arrangement that would have been very difficult to decipher by other
procedures.The solution of the arsenoclasitestructure also adds confidence to the application of direct methods to noncentrosymmetric
mineral structures.
The perfect cleavageparallel to [ 100] is explicable in a relative sense
since this plane is parallel to the axis of the chains (6) and the axis normal to the close-packedlayers (c), the directions of strong Me-O-l\{e
bonds bridging between the chains and the oxygen layers.
INtnnnroltlc
DTsTANCES
analysisof Blix in Aminoff (1931)indicatesthat the
The arsenoclasite
The reasoncompound is nearly pure stoichiometricMns(OH)a(AsOn)2.
COORDINAT ION IN ARSENOCLASIT I'
t.s47
.':'.t:;
".::l:,i
:.:'..
Ifrc.3. rdealized polyhedral chains which are the components of the arsenoclasite
structure projected down the c-axis. Ali chains run parallel to the 6_axis.
a The wall of alternate one- and two-octahedra, comprised of the Mn(2)-, Mn(3)_
and Mn(4)-oxygen octahedra.
b. The corner-sharing chains of Mn(l)v-g trigonal bipyramids (stippled) and As(2)-o
tetrahedra. Note the presenceof Mn(1)-Mn(1)-As(2) three-membered rings.
c. The corner-sharing chain of alternate Mn(5)rv-g trigonal pyramids (stippled) and
As(1)-O tetrahedra.
able isotropic thermal vibration parameters for all ionic speciesattest
to an orderedstructure and the essentialabsenceof substitutins cations
of different atomic number. we shall discussthe interatomic Jistu.rces
on the basis of an electrostaticmodel.
MOORE AND MOLIN-CASE
1548
-l
It
I
F
cl
I
B
Frc.4. Orientation of the geometrically equivalent octahedral walls in arsenoclasite
(A) and pseudomalachite (B). The walls run perpendicular to the plane of the drawing
and the connections between centers of the two-octahedra in the wall are drawn as bold
Iines.
According to such a model, effectson the Me-O distancesshould be
noted if the anions are undersaturatedor oversaturatedelectrostatically
with respectto cations.Table 4 revealsthat O(12), O(5), and O(7) are
- '35, and -'42 respecconsiderablyundersaturatedwith A2: -.25,
tively; whereasO(6) and O(9) are considerablyoversaturaledboth with
A>:+0.25. The remaining cations deviate only slightly from electrostatic neutrality.
Table 5 presents the Me-O and O-O' polyhedral distances in the
arsenoclasitecrystal structure. The polyhedral averagesare Mn(1)v-O
2 . 1 9 ,M n ( 2 ) v r - O 2 . 2 5 ,M n ( 3 ) v r - g 2 . 2 2 ,M n ( 4 ) v r - O2 ' 1 9 ,M n ( S ) w - O 2 ' 1 3 ,
As(1)N-O 1.67 and As(2)rv-O1.694. T'he Mn2+vI-Oand As5+Iv-Oaveragesare typical for their polyhedraand have beenrecordedfor numerous
slructures. T\he Mn2+v-O trigonal bipyramidal average is considerably
longer than the Mnv-O 2.t2L distance in eveite, Mnz(OH)(AsO+) (an
isotype of andalusite) reported by Moore and Smyth (1968), but the
environments in the two structures are quite different' The Mn2+rY-O
distanceis considerablylonger than the Milv-O 2.04h tetrahedron re5+As5+O1z'
port ed by Moor e ( 1970c) f or manganostibite, M nl+vt1'1tt3+tvsb
It is difficult to suggest reasons for these differences without much
speculation since the number of refined structures with Mn2+ in tetrahedral or five-fold oxvgen coordination are few and no survey is practicable. Geometrically, the trigonal bipyramid is capable of continuous
distortion and passesinto the square pyramid. As for Mn(S)N-O in
COORDIN AT ION I N ARSENOCLASITIJ
1549
F_b________r
Frc. 5. Idealized polyhedral diagram of the arsenoclasite atomic arrangement down
the c-axis, built Irom the components in Figure 3. AII Mn-O polyhedra are stippled and
the As-O tetrahedra are unshaded. The Mn(2)-, Mn(3)-, Mn( )-O octahedral wall is centered at s-f. Labelling of the atoms conlorms to trre convention in Table 5. comprehension of the three-dimensional polyhedral arrangement is further assisted by Figure 2.
arsenoclasite,the coordination polyhedron deviates considerably from a
cation-centeredtetrahedron since Mn(5) residesnearly in the plane of
the base. For geometrical discussion, the oxygen polyhedron is tetrahedral in shape, but from an electronic standpoint, it is more properly
MOORE AND fuIOLIN-CASE
1550
TABLE II.
ARSENOCIASITE: ELECTROSTATICVALENCE BAIANCES (E)
ABOTN ANIONSA
tr
0H(1)
lfrt(1) ++.{n(2)+}art(4)
)/\+2/R+)/6
1.07
^E
+.o7
oH(2)
Mn(3)+Mn(q)+l4n(s)
I'4n(2)+I4n(2)+Mn(t+)
7/6+2/6+2/_+
I
2/6+u6+2/6
I.L7
oH(3)
r.00
+.00
oH(4)
I"h (3) +l4n(+) +Mn(s)
2//6+2/6+u4
1.17
+.I7
f .65
- .35
1.58
-.+2
0(s)
As(2)+Ifrr(I)
s/++2/s
o(6)
As(2)+tln(2)flan(3)+Mn(t+)
5/4+u6+2/6+2/6
o(7)
As(2)+!an(3)
5/++2/6
o (8)
As (2) +[,ln(1) +!h (])
5/++Us+U5
o (9)
As (l) +r'h (2) +I&t(3) +Mn(r+)
5/++U6+U6+?/6
o(10)
As(1) +lan(3)+Ifrt(s)
s/4+U6+U+
2.08
+.08
o(11)
As (1) +Ian(l-)+lan(2)
V4+Us+U6
1.98
_.02
o(12)
As(1)+[an(s)
5/++2/4
r.75
nq
"
+.05
+)<
+0.00
uTh"
,AE
for
severely
oversaturated
or undersaturated.
anions
are italicized-
a trigonal pyramid. The distinction betweenMn(1)Y-O and Mn(5)Iv-O rech''' ).
h e s t a c k i n g s e l l u e n( c' ' e'
s u l t s f r o m t h e i cr a t i o n l o c a t i o n s ti n
Mn(1)v is located at z-|- and t, which in Figure 1 are the centersof the
hexagonalclose-packedblocks and the cation must coordinateto apical
anions above and below. Mn(S)Iv however, is located at z-0, |, which
are centers of the cubic close-packedblocks' Consequentlv, Mn(5)rv
coordinates to an apical anion above (below) but the apical anion
below (above) is not present.
The only polyhedra which share edgesare the Mn(2)-, Mn(3)- and
Mn(4)-oxygen octahedra.As shown in Table 5, shared edgestend to be
among the shortestfor their polyhedra.The effectsof electrostaticdeviations from neutrality about anionsare also apparent: the undersaturated
anions show short Me-O distanceson the average,whereas the oversaturated anions have longer Me-O distances than average. These
accord with generally observedtrends in oxysalt crystals add yet further
confidenceto the contention that three distinct coordinationpolyhedra
for Mn2+ occur in arsenoclasite.
CCORDINAT| ON IN ARS|I:,NOCLASITE
lJ.) I
o!
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3 3 I ll3
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E R F R R $lR
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d - - - t H N N N N N N I N
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F a r
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d
MOORE AND MOLIN-CASE
1552
AcKNowr-EDGEMENTS
This study was supported by a Dreyfus Foundation grant and the NSI' grant GA10932 awarded to the senior author.
Rllrpnxcrs
AurNonr,, G. (1931) Arsenoclasite, a new mineral from Langban. Kungl. st'ensha vetenskaPsakad..II and'I. 9, 52-57 .
Bntnv, L. G. (1950) On pseudomalachiteand corne tite. Amer ' Mineral.35,365-385'
-(1g51) Observations on conichalcite, cornwallite, euchroite, liroconite and olivenite.
Amer. Mineral 36, 484-503.
BunNneu, C. W (1963) An IBM 7090 computer program for computing transmission
factors for crystals of arbitrary shape. Author's copy'
Busrnc, W. R., K. O. Mlnrrw, eNnH. A. Lrw (1962) ORI'LS, A Fortran crystallographic
Fed. Sci.. Tech.
least-squaresprogram. Lr.S. Oah Rid.geNat. Lab. (U.5. Cl,eari,nghouse
p
I nf o.) Re ORNL-TM-305'
c.rnarr, L. D. .rnn W. H. BanNns (1957) The structure of lindgrenite can. Mineral'.6,
.t l-J
r.
Ahmad, ad',
Dnw.r.n, R. B. K. (1970) A system of direct methods programs. InF'F.'
Crystdl'ogrophie C omputing,Munksgaard, Copenhagen, 63-65'
FrrNx, G. (1924) Om sarkinit frin Lingban, ett ftir fyndorten n)'tt mineral. Geol. Fijren.
Stockh. F'drhandl'. 46, 661.
GHosn, S. (1963) The crystal structure of pseuclomalachite,Cu5(POo)r(OH)r.Acl'o Crystallogr. 16, 124-128.
(1964) The crystal structure of hydrozincite, Zns(oH)o(cot)2. Aclo Crystall'ogr.
17, 1051-1057.
Moonr, P. B. (1967a) Crystal chemistry of the basic manganese arsenate minerals. I.
Crystal structures of fl inkite an d' r etzian A m er. M in eral' 52, 1603- 1673'
(1g67b) Contributions to Swedish mineralogy. L Studies on the basic arsenates of
---
manganese. Ark. M i'neratr.GeoI. 4, 425-444.
(lp68a) Crystal chemistry oI the basic manganese arsenate minerals. IL Crystal
structure of allactite. Am er. M ineral. 53, 733-7 41.
(1968b) Crystal structure of chlorophoerricite Amer. Mineral-\3,111o-1119'
(1g70a) Crystal chemistry of the basic manganese arsenates. IV. Mixed arsenic
valences in the crystal structure of synadelphite . Amer. Minerd.55,2023-2037 .
(1970b) Edge-sharing silicate tetrahedra in the crystal structure of leucophoenicite.
Amer. Minual,. 55, 114G1166.
(1970c)Manganostibite: a novel cubic close-packedstructure twe. Amer. Mineral.
55, 1489-1499.
eNn J. R. Sarvrn (1968) Crystal chemistry of the basic manganese arsenates' III'
The crystal structure of eveite.,4mer. Mineratr.53' 1841-1845'
Per-acrn, C., H. BrnueN, axn C. FnoNoBr- (1951) Ifta Sys,em,oJ Mineralogy ' ' ' oJ Dana,
-
Vol. 2. John Wiley and Sons, New York, 800-802.
Srnurz, H. (1970) Minerdogische Tabe)l,en, 5. Aufl. Akademische verlagsgesellschaft,
Geest und Portig K.-G., LeiPzig,320.
wrr,so r, A. J. C. (1942) Determination of absolute from relative X-ray intensity data
Not.we l5O, 151-152.
Manwscript receh.td, February 22, 1971; acceptd Jor publi.calion, April 14, 1971'