American Mineralogist, Volume 59, pages 48-59, 1974
l. Jahnsite,Segelerite,and Robertsite,Three New
TransitionMetal PhosphateSpecies
ll. Redefinitionof Overite,an lsotypeof Segelerite
Pnur BnnN Moone
Thc Departmcntof the GeophysicalSciences,The Uniuersityof Chicago,
Chicago,Illinois 60637
ilt. lsotypyof Robertsite,Mitridatite,and Arseniosiderite
Peur BmaN Moonp
With Two Chemical Analvsesbv
JUN Iro
Deryrtrnent of GeologicalSciences,Haraard Uniuersity,
Cambridge, Massrchusetts 02 I 38
Abstract
Three new species,-jahnsite, segelerite, and robertsite,-occur in moderate abundance as late
stage products in corroded triphylite-heterosite-ferrisicklerite-rockbridgeite masses,associated with
leucophosphite,hureaulite, collinsite, laueite, etc.Type specimensare from the Tip Top pegmatite,
near Custer, South Dakota.
Jahnsite, caMn2+Mgr(Hro)aFe3+z(oH)rlPC)oln,a 14.94(2),b 7.14(l), c 9.93(1)A, p 110.16(8)",
P2/a, Z : 2, specific gavity 2.71, biaxial (-), 2V large, e 1.640,p 1.658,t l.6lo, occurs abundantly
as striated short to long prismatic crystals, nut brown, yellow, yellow-orange to greenish-yellowin
c o l o r . F o r m s a r e c { 0 0 1 } , a { 1 0 i0l 2
} ,o l l , j l 2 } l l , f t [ i o l ] , / t o l l l , n t 1 1 0 ] , a n d z { i t t } .
Segeierite,CaMg(HrO)rFes+(OH)[POdz,a 14.826{5),b 18.751(4),c7.30(1)A, Pcca, Z : 8, specific
gaavity2.67, biaxial (-), 2Ylarge,a 1.618,p 1.6t5, z 1.650,occurs sparingly as striated yellow'green
prismatic crystals,with c[00], r{010}, nlll0l and qll2l } with perfect {010} cleavage'It is the
Feg+-analogueofoverite; a restudy on type overite revealsthe spacegroup Pcca and the ideal formula
CaMg(HrO)dl(OH)[POr]r.
Robertsite,carMna+r(oH)o(Hro){Ponlr, a 17.36,b lg.53,c 11.30A,p 96.0o,A2/a, Z: 8, specific
gravity3.l,T,cleavage
[l00] good,biaxial(-) a1.775,8 *t - 1.82,2V-8o,pleochroismextreme
(Y, Z = deep reddish brown; 17 : pale reddish-pink), @curs as fibrous massesand small wedgeshapedcrystalsshowingc[001 f , a{1@}, qt031}. It is tabular paraltelto {100}. The color is shiny
black, blood-red in thin splinters, streak chocolate brown.
Mitridatite, carFes+n(oH)o(Hro)glPodr, a 17.52(2),b lg.1r4), c 11.25(2)4, p 95055" A2/a,
Z :8, specificgraity 3.24,a1.785,F o t : 1.85,2V 5-10o,pleochroismextreme(Y' Z - deep
greenish-browl, X : pale greenishyellow), shows a{100},^c{001} arrd ul423l. Arseniosiderite,
carFes+(OH)o(Hp)glAsOrlr has a 17.76, b 19.53, c 11.30A, p 96.00basedon the powder data.
These speciesare isotypes of the robertsite structure.
oped crystals. It is approPriate,for this reason, to
commencewith a detailed description of the paraRarely doesan investigatorin descriptivemineral- genesisof these minerals since their compositions
ogy have an opportunity to announcethree species leave little doubt that their formation was due to the
new to scientific intelligence which not only occur presenceof Caz', Fe3*,Mn2', Mnt*, Mg'*, [POn]t-,
intimately associatedbut also appear as well-devel- and (OH)- ions in solution at low temperature.
Introduction
48
THREE NEW TRANSITION
Following this paragenetic discussion, the crystal
chemistry of each speciesshall be discussedseparately.
The type specimensoriginate from the Tip Top
pegmatite,near the village of Custer, in Custer
County, South Dakota, although other localities
have also cometo light and one species(robertsite)
(mitridatite) so widespreadin
has a Fes*-analogue
its occurrenceto suggestthat the phaseshould elicit
considerableinterest in its crystal chemistry.The
Tip Top pegmatite(NE 7a, SW 7+, sec. 8, T.4S,
R.4E) is one of severalin the regionof the central
Black Hills where a great abundanceof triphylitelithiophilite appeared as an accesorycore mineral
arrd was exposedduring the course of mining activity. These crude giant crystals of triphylite suffered
extensiveretrograde oxidative and metasomaticreactions which resulted in the ferrisicklerite-sicklerite
seriesLi1-,Fe3*,(Fe2*,Mn'-)r.-r[POa];
the heterositepurpurite series (Fe3*,Mn3*)tPOn];and the rockbridgeite-frondelite series (Fe,Mn),-Fe'.r(OH)s
[POrle.Vuggy cavitiesin thesephasescontaina host
of late stage hydrated transition metal phosphates.
Since casual inspection of such associationscan be
unreliablein identificationof species,greatcarewas
taken in this study to examineall distinct phasesby
X-ray single crystal and powder diffraction techniquesand, whenevernecessary,
to establishidentity
by comparison with descriptionsof type materials.
Phasesdiscoveredin thesecavitiesincludeleucophosphite, KFe3.2(OH)(HzO)[POa]z.HzO, as lovely
greenish-grey,purplish-pink to deep amethystine
prismatic crystals; hureaulite, (Mn,Fe),-s(HzO)n
[PO3(OH)]2[PO+]2,as pale yellow, to pale pink to
red-brown prismatic crystals; collinsite, Ca2(Mg,
Fe") (H2O)s[POe]2,as colorlessto white radiating
sprays,lath-like crystals,and flattened chiselshaped rosettes;hydroxylapatite,Cad(OH)[PO+]s,
as rounded colorlesshexagonalprisms; whitlockite,
ca Ca6Mg[PO+]e,as colorlesssimple rhombohedra;
bermanite,Mn2'Mns-2(OH)r(HrO)n[POn]e,
as deep
reddish-browndrusesof thin tabular crystals;laueite,
Mn2-Fe3.2(OH)z(HzO)o[POl]z.2HzO,as striated
orange laths; mitridatite, Ca3Fes-a(OH)u(HrO),
[POn]n,as thin brittle greenish-brownplatesand dull
olive-greenstains; and the new speciesjahnsite,
( OH ) 2[PO4]4
CaMn'.Mp ( HzO) eFe3.z
; segelerite,Ca
Mg(H2O)aFe3.(OH)[POe]zi and robertsite, Cas
Mn3"a(OH)6(HrO)s[PO4]r.For a generalreviewof
the myriad pegmatite phosphates,the reader is referredto Moore (1973).
METAL
PHOSPHATES
a. The aquated oxidaion products of triphylitelithiophilite
The secondaryphosphateparagenesisof the Tip
Top pegmatiteappearsto fall into two closelyrelated
but distinct categories:the products of direct solution, oxidation, and recrystallizationof the parent
triphylite-lithiophilite and the products involving the
addition of Ca2*and Mg2*cations.We haveexamined
by electron microprobe analysis remnant primary
triphylite occurring in the interior of the zone of oxidation and aquationand have obtainedthe composition Li(Fee7sMns.22Mg.o.ro)[POn].
Since the late
stageCa-Mg rich phosphatesoccur locally but occasionally in sufficientabundance,it is difficult to imagine a contribution of the Ca2*and Mg2-cationsfrom
the parent phosphates;it is proposedthat thesecations were introduced at alate stagefrom a separate
source and were added to the pool of cations provided by the the parent phosphates.
The oxidation and aquation of triphylite leads
directly to the formation of rockbridgeite or ferrisicklerite, where ferrisicklerite may in turn be oxidized further to heterositeor aquatedto,form rockbridgeite. These phasesare observed as among the
most persistent products of oxidation-aquation of
triphylites in granitic pegmatites throughout the
world. Since the isoelectronicpoint of Fe3* cation
occurs at lower pH valuesand earlier than Mn2* and
the Fe2' remaining, leucophosphite crystallizes at
low temperatureswhere water ligands are stable.
The solution becomesprogressivelyenrichedin Mnz*,
which crystallizes later in hureaulite. At the final
stages,laueite and mitridatite appear.Here, oxidation
may produce Mn3*, so that bermanite forms. With
the depletion of [POa]'-, todorokite, ca Mn.s (O,
OH)16.2H2O, crystallizes.Thus, the sequencetriphylite-ferrisicklerite- rockbridgeite- leucophosphite,
hureaulite * laueite-mitridatite-bermanite-todorokite
appearsrepeatedlyat the Tip Top, White Elephant
and Linwood pegmatitesin the Black Hills; at HagendorfStid, Bavaria; at PalermoNo. 1, New Hampshire; and at the Sapucaiapegmatite,Brazil.
b. The addilion ol Cazrand Mg*
Collinsite, hydroxylapatite, whitlockite, and the
three new speciesare not rare at the Tip Top pegmatite. In addition, they have been observedfrom
the White Elephant pegmatite,having formed under
similar conditions. Mitridatite is a particularly persistent phase at all stagesof late crystallizationand
PAUL B, MOORE
50
occurswidely as stainscoatingthe silicatessuffounding triphylite crystals at practically every pegmatite
where triphylite occurs, suggestingthat mitridatite
is an important low temperature phase. Paragentically, the Ca2*-and Mg'Lbearing minerals occur at
the sequencewhere leucophosphiteand hureaulite
crystallized. Robertsite appears in several generations: as shiny black botryoidal aggregatescoating
the cavity walls upon which are implanted jahnsite
and collinsite, and as reddish platy rosettes implanted upon theseminerals.In severalspecimens,it
occurs as the sole mineral with stubby shiny black
crystalslining the cavitiesin the same.
wedge-shaped
and whitlockite usually
hydroxylapatite,
Collinsite,
to
as
the
last
minerals
crystallize,encrusting
appear
jahnsite.
The author suggests
the rather abundant
that the Fe3* remaining in solution crystallized as
jahnsitewith the essentiallypure Ca-Mg phosphates
crystallizinglast.
quently occur as parallel aggregates,twinned by
reflectionon c[001]. Large crystalsmay be up to
5 mm in length, though 0.1 to 0.5 mm are most
typical. The forms includec{001f, c{100f, t{2011,
jlz}rl, k{iol}, /{0lrl, m{llof and nIill] with
striaeon jlz0ll and all00l. A typical development
is presentedin Figure l.
Analysis of the reticular density (based on the
X-ray cell) reveals that the form frequenciesapproximately follow the order of descendinginterplanar spacings(Table la). The form blOlOf is
consistently absent; examination of single crystal
data revealsthat this plane is of zero intensity.Table
la suggeststhat some crystals of jahnsite should
reveal l2llf and {lll}, but none of the crystals
submitted to morphological examination presented
thesefacets.
X-ray data
A partly indexed powder pattern is oftered in
Table 2a. Caution was taken to roll the ground sample into a small spherewith rubber cement.Throughout this study, the powder data were indexedon the
D escriptiue mineralogy
basis of the stro,ngsingle crystal intensities.CompuThe new speciesjahnsite occurs as tabular short tations of the interplanar spacingswere made from
to long prismatic crystals with vitreous to subada- the single crystal studies.
Table 3a provides the structure cell data. In admantine luster of a nut-brown, purplish-brown,yelwe have solved its crystal struotureand have
dition,
low, yellow-orange,or greenish-yellowcolor. It can
refined
the results to R(hkl) = 0.09. This allows
be easily confounded with laueite, pseudolaueite,
stewartite, and childrenite. Experience has shown
that almostcertain distinctionfrom theseother phosphates can be achievedby analysisof crystal morphology. Persistentstriations parallel to the prism
(=[010]) distinguishit from hureauliteand leuco
phosphite.Laueite and stewartiteusually revealtheir
triclinic character.Metastrengiteusually possesses
a
delicate pink color not observedin jahnsite. Childrenite in well-developedcrystals almost invariably
shows good orthorhombic development with persistentp{lII} and s{121}.
The specific gravity of jahnsite is 2.706 (pycnometer), 2.718 (sink-float in methyleneiodidetoluene), computeddensity 2.715 gm cm-3, hardness4, cleavage{001} good.The mineralis soluble
in dilute HCI solution.
JAHNSITE
CaMn2*Mgr(Hro),Fe' *r1oH;,1POn1,
Crystal morphology
Crystals are commonly well-developedand euhedral, monoclinic holosymmetric (2/m), striated
parallel to [010], short to long prismatic parallel
to [010],often tabular parallelto a{100f. They fre-
AB
FIG. l. Crystal of jahnsite showing the forms c {001}, a { 100}'
i ! 2 } r l , j l z o l l , & { i 0 1 l , l { 0 r 1 } , n { 1 1 0 f, a n d z { i l l } . T i p T o p
pegmatite. A. Plan. B. Clinographic projection.
THREE NEW TRANSITION METAL PHOSPHATES
Tnnr.B l. Jahnsite and Segelerite. Descending Interplanar
Spacings, Intensities, and Appearance of Forms
SEGELERITE
JAHNSITE
hkl
001
d(hkl)
9.32
Appearance*
l/Io
10
0I0
7.14
< I
200
7.01
I
20r
6.85
< r
rl0
6.36
Z
llr
5.68
0lr
x
hkl
d (hkl)
I/Io
<l
010
18.75
020
9.38
e
200
7.rrl
<I
2r0
6.89
<t
030
6.25
<I
< ll
t1r
6.19
<r
5.67
< 4
220
5.82
I
2r0
5.0r
< I
l2t
5.37
6
2lt
q.gq
< 6
rlr
q.gr
< 6
20r
q.86
< I
202
4.70
< 1
Appearance
5l
Mg-O octahedra in the structure, we propose the
( OH ) ?[PO4]4,
ideal formula CaMn2.Mg2( IIpO ) gFe8.e
of which there are two formula units in the cell.
*
x?
Optical properties
The type sampleis biaxial (-),2V large,c 1.640,
1.658,
y t.67O, all -F 0.003. For the brown crysB
tals, absorption is Y >> Z > X, with X pale pulple,
Y deep purplish brown, and Z yellow with a tinge of
green.Z is llb and X A c ca 18". Based on the
Gladstone-Dale relationship, the tables of Larsen
and Berman (1934), the ideal fonnula, and the average observedspecificgravity, (n) calc = 1.668.
Tlrr"e 2. Jahnsite and Segelerite. Powder Data
*G=prese4t,a=ab6ent)
a.
!/I_g
for a precisedescriptionof the jahnsitecrystal chemistry and the establishmentof a correct formula,
which otherwisewould be a difficult and uncer,tain
problem. Chains of Fe3.-OH-Feg* corner-sharing
octahedra run parallel to the b-axis and link to
[PO+]* tetrahedra; alternating Ca-O and Mnz'-O
distorted octahedraledge-sharingchains also run in
the hdirection, forming denseslabsparallel to {001}.
These slabs are bridged by the [POn]* tetrahedra
which link by corners to the aquated Mg-O octahedra. The structure reveals a novel ligand stereoisomerismabout the octahedralcorner-chainswhich
was predicted on combinatorial grounds by Moore
(1970). It is allied to the childrenite-eosphoriteand
laueite-pseudolaueite
structures.
Chemical analysis
Several electron probe analysesof jahnsite were
made by Mr. T. Solberg utilizing apatite, wollaste
nite, wyllieite, and MgO standards.Owing to the
brittle characterof the crystals,the jahnsite samples
were not polished and consequentlythe quantitative
results in Table 4a arc consistentlylow. Thus, computations of the cation composition were based on
an integral number of phosphorus atoms. Valence
stateswere inferred by the crystal structure analysis
and the water content was determinedby the Penfield tube techniqueconductedby Dr. A. L. Lingard
of South Dakota School of Mines and Technology.
SettingP = 8.0, the analysiscomputesto
JAHNSITE
d(obs)
b.
d(calc)
!\l
!/!S
SEGELERITE
d(obs)
!!l
9.320
001
9
9.3I
9.376
.I
7.08
7.OI2
200
I
5.7rt
5.815
220
2
6.12
6.360
II0
t2l
5.6b
s.683
l-It
5.34
q.97
5.372
4
6
q
s,667
0lI
q
9.65
5.01-q
q.688
0't0
9.9 r{2
2LI
2
3.936
3.962
2{r0
r+.908
III
5
3.706
3. 'rq6
400
q20
3.255
4tl.
3.224
2L2
q30
6 brd
q.9I
020
zLL
q
q.63
q.660
002
5
3.7 29
3. q2I
3
3
I
5
q.05
rt.075
II2
2
3.253
3.90
3.91-0
3.723
3.733
3I0
qol
I
3.s22
3.5qo
3rz
q00
3
3.059
3.083
3.506
r0
2.868
2.907
3r+l
qqo
3.163
3.18S
3
3.q16
3.q26
q02
2.882
0q2
3
3.268
3.28q
3II
2
2.813
2.82L
2
3.I6s
3.165
4
2.583
2.577
I6t
rrtz
5
2.950
2,962
22I
r+01
3 brd
2.368
2.389
q60
8 brd
2,825
2.A6?
403
2.379
062
2.833
022
q2r
3
2.107
2.296
I
2.253
2.275
2L3
qq2
3
)
2.f91
) tt1
2.060
tt
2.575
2.579
2
2.t1I7
2.q24
3
2.3rt1
2.3r+9
402
q04
2.340
6r.r
r
2.122
612
I
2.026
c
1,988
3
2.002
2.007
tt22
2.007
q03
c
1.963
3
q
1.958
1.962
qzq
I
r.925
.r.gqs
t.95I
02q
lteo?
I.9q7
405
3
1,8'+q
4
1.870
1.866
802
3
1.819
1.78rr
0rr0
2
I.787
3
r.733
r
L.777
2
r.697
2
I.746
r
I.667
2
r.608
r
I.593
2
1
1.5r+0
t qtq
I
2lu?q
l.tt49
3
r.3r+6
r
.1.669
r
q
1.6q2
'r
I.5r+8
1.573
3
I.52q
3
l.rr95
+ 20 line6,
-Iess than 3
Ca2.eMn2*2.sMg.rFet*a.sAlo.
s
(oH)4.1[PO4]8.o.
15.8H2O.
2
I
2
1.305
3
1.296
3
t.25q
+ 15 linesr
Noting that all water molecules are bound to the
d(calc)
9.27
(Fe,/Mn racliation,
ll4.6m
camera dimeteri
filr
lqq
Iess than 3.
corrected
for
shriikage)
PAUL B. MOORE
52
Tasln 3. Jahnsite, Segderite, and Overite. Structure C-ell Data
a.
e6)
ldl
sdl
F
b.
JAHNSITE
SEGELERITE
c'
oVERITE
I4.e4 (2)
t + . 8 2 6( s )
rr+.78
7 .14 (1)
18 .7 51(r+)
18.78
e . e 3( r )
(L)
7 .3o_7
7.lll
l-10.16(8) o
specific
dssity
Pcca
PUa
space group
z-o I
2.53
2.7L5
2.610
2. q8
caMg.(Hao),!hz+re:+ (oD 2[ Po4] rl
2
caMs(HzO)+Fe3+(OD t PO4l2
8
(Hro)uAr(olDI Poq]2
car-rg
gravity
2.706t 2.7!8
(em crfl
fomla
Tip
Top pegmtite.
Refined
coordinates
frcm
PAILRED diffractometer'
h
Tip
Top pegmatite.
Refined
coordLnates
fM
flICXER diffractometer'
c.
Fairfield
Utah.
Axia1
Pcca
itv
data and
of
I
Iarsen
variable amount at the White Elephant,Bull Moose,
Chief, and Linwood pegmatitesin the Custer
Big
Jahnsite is a relatively abundant mineral in the
region
of South Dakota, invariably with hureaulite
low temperature phosphateparagenesisat the Tip
and leucophosphite.At the Linwood pegmatite,much
Top pegmatite.It usually occurswith leucophosphite,
of the bright yellow friable material filling cavities in
hureaulite, and collinsite, but granular massesup to
and associatedwith collinsite and robertheteroeite
5 cm acrossconsistingsolely of the new mineral fill
site provides a powder pattern identical with jahncavities in ferrisicklerite. These massesare aotually
site. Nut-brown striated crystals occur as warty agdenselyinterlocking turbid dull yellow-orangecrysgregateswith laueite and strunzitefrom the Palermo
tals invariably twinned on {001} resulting in a
1 pegmatite,North Groton, New Hampshire.
No.
pseudo-orthorhombicappearance.It also occurs in
A related compound occurs in moderate abundanceas orangesplintersintergrownwith 1= replacTlst.n 4. Jahnsite, Segelerite,and Overite. Chemical Analyses
ing?) coarse fibrous black rockbridgeite from the
Fletcher pegmatite,North Groton, New Hampshire.
c- oVERITE
b.
SEGEIERITE
a. JAHNSITE
It correspondsto the "golden rockbridgeite"of New
123456
England collectors. The unit cell and space group
15.I
16.1
I4.0
13.6
6.6
6.9
CaO
are similar to those of type jahnsite, but the optical
1r.2 10.9
10.r
9 .s
9.4 9.9
Mgo
and physical pro,pertiesindicate a different composi0.0
8.7
8.0
WrO
tion. This may be related to'the "xanthoxenitelike
20.0
1 6. 4
15.l
19.6
Fe20
phase"incompletelydescribedby Mrose ( 1955). Yet
3
13.7
)1
13.7
0.q
A1203
anotherrelatedphaseoccursas tan, tabular, twinned
3
8
3
8
.
3
1
5
.
9
3
3
.
1
.
6
P-0.
crystals coating rose quartz from the Taquaral peg2
2
.
O
2
2
.
O
C
20.3
1 9. r
19.9
matite, Minas Geraes, BtaztT. It, too, provides a
18.8
Hzo
structure cell akin to jahnsite, and Anr electron
10r.9 100.0
92.I I00.0
92.2 100.0
probe analysisshowsthat it is the aluminumanalogue
IARL
Unpolished
as oxides.
conputed
probe
analysis
electron
Penfield
by
Water detemined
malyst.
T. Solberg,
of jahnsite. Both compounds are presently under
crystals:
A. Lingard,
analyst.
tube:
further investigation.
Occurrences
2For caMs2
(oH)2[ Po4l4.
(Hzo)sr'.r.r2*F":+
3See
it;.
qror
v,later
detemined
by
weight
loss
upon
caMg(Hro)
ure3+1otqIroulr.
SARL
probe analysis computed as oxides.
ulectro.
A' J. Irving'
Larsen (1940). Polished crystal:
6For
fusion.
CaMg(Hro)uAtioHlIro,r) r.
l'later from
analyst.
Name
The Commissionon New Minerals and Mineral
Names (IMA) has approved the name jahnsite
prior to publication. It is a pleasureto christen this
magnificentspeciesiahnsite after ProfessorRichard
THREE NEIY TRANSITION
METAL
PHOSPHATES
53
that of overite. Overite was described as a new
speciesby Larsen (1940) who proposedthe formula
Z = 2, and the cell
CagAle(PO+)r(OH)o'15HrO,
SEGELERITE
dataa 14.75,b 18.74,c 7.12 A, spacegroupBmarn.
Through the assistanceof Mr. John S. White, Jr.,
CaMg(HrO)rFe'*(OHXponl,
we obtained some single crystalsfrom the type material, bearingU.S.N.M. No. R7898. X-ray, WeisD escriptiaemineralogy
senberg,and precessionphotographsabout the c-axis
This new species closely resemblesjahnsite, to
conclusivelyshow that the spacegroup is Pcca,idenwhich it is chemically related, but is easily distintical with that of segelerite.Recently, we examined
guished by its relatively simple orthorhombic morthe crystal chemistry of overite by electron probe
phology, pale green color, and long prismatic deanalysis,following the proceduresused for jahnsite
velopmentwith nearly squarecross-section.
Segelerite
and segelerite.The original formula is in error:
appears to be much less frequent than jahnsite; it
overite
is the aluminum analogueof segelerite,with
occurs as striated prisms along joint fractures in
the formula CaMg(IIrO ) 4Al (OH) [POdr.
dense ferrisicklerite-rockbridgeite,usually in close
The overite analysiswas performed by Dr. A. J.
association with collinsite, minor hydroxylapatite,
Irving who used diopside,anorthite, and wyllieite as
and globules of red-brown robertsite. The color is
standards.Since the crystal of overite was polished,
pale yellow-green, lively chartreuse, inclining to
it provided excellent results as shown in Table 4c.
colorless.The cleavageis {010} perfect,hardness4-,
specific gravity by sink-float in methylene iodideChemical arnlysis
toluene2.67.The computeddensityis 2.610gm cm-s
based on the structure cell and ideal formula. It is
Anr electron probe analysesrun simultaneously
solublein dilute HCI solution.
with the jahnsite on several small single segelerite
crystalsgave the resultsin Table 4b. The water conCrystal morphology
tent was determinedby weight loss upon combustion
since there was no evidence for oxidizable ionic
Crystalsare up to 0.5 mm in length; orthorhombic
species.
(2/m 2/m 2/rn), and striated parallel to the prism
Based on P = 16.0, the cation ratios establish
which is [001]. The cross-sectionshows a nearly
Cas3Mg6.6Fe3.z.
rAlo.r['POn]te.
o( OH ) z I' 30.7 H2O
square outline, with lustrous a{ 100}, D{010},
ideal
formula
CaMg(HeO)
the
suggesting
aFes-( OH )
m{IlO} and.q{l2l}. A typical developmentis shown
the
units
in
cell.
with
eight
formula
in Figure 2. The analysisof reticular densityin Table [POn]2,
H. Jahns, outstanding scholar of pegmatites, and
Dean of Earth Sciences.Stanford Universitv.
1b showsthat the developmentconformsto the space
group and structure cell shape.
X-ray data
A partly indexed powder pattern is offered in
'Iable
2b, and the singlecrystal study is summarized
in Table 3b. We note that the structure cell is related to that of jahnsite,but it is not possibleto transform the jahnsite structure into that of segelerite
continuously without changes in order of ligand
groupingsaround the Mg-(O,HzO) octahedra,and
we concludethat a stereoisomericrelationshipexists
between the two species.Toward this end, we are
investigatingthe structure of segelerite.
Ooerite: an isotype
We mention the closesimilarity betweenthe structure cell and crystal morphology of segeleritewith
AB
Fro. 2. Crystal of segeleriteshowing the forms D{010}' a { 100| ,
mlll}l,
and qll2l |. Tip Top pegmatite. A. PIan' B.
Clinographic projection.
PAUL B. MOORE
Optical properties
The type segeleriteis biaxial (-), * 1.618,p
1.635,y 1.650 -r 0.003, 2V large.The absorptionis
with X: b,Y = a,
Z (yellow)> X,Y (colorless),
Z=c.
Occurrence
So far, the Tip Top pegmatiteis the only locality
for segelerite.It usually occurs in intimate association with collinsite and hydroxylapatite. According
to the crystal structure analysisof jahnsite, the ordered Mn2* cations evidently stabilize that mineral.
Sincejahnsite is evidently rather abundant,sufficient
Mn2*was apparentlyavailablein solution to promote
its formation. As Mn2* is depleted,segeleriteforms,
providing there still remain some Fe3' cations in
solution. Segeleriteappearslater than jahnsite and
for this reasonis found in close associationwith the
Ca-Mg phosphatesrather than leucophosphiteand
hureaulite which have crvstallized earlier with the
jahnsite.
Name
The Commissionon New Minerals and Mineral
Names (IMA) has approvedthe name prior to publication. The lustrous well-developedcrystalsof this
new phosphate segeleritemake it fitting to honor
Mr. Curt G. Segelerof Brooklyn, New York, amateur mineralogist,whose superb collection of micromounts, especiallyof pegmatiteplosphates, reveals
the care and meticulousnessof his mineral identifications through optical and microchemical techniques.
ROBERTSITE
ca, Mn' *o1oH)6(Hro)3
[ Po4]4
D escrip ti te mineralogy
Robertsite is moderately abundant, at least locally, and is probably rather widespread,especially
in pegmatiteswhere triphylite occurs in abundance.
It is easilyconfusedwith the rockbridgeite-frondelite
group of minerals, which commonly occur as shiny
black to deepreddish-brownfibrous masses.The key
differencesinclude color and specific gravity. Rockbridgeite sliversare bluish to greenishin tint; robertsite is reddish-brownto deepblood-red.In methylene
iodide, fragments of rockbridgeite-frondelite sink
while those of robertsite (and mitridatite) float.
Robertsiteoccurs as fine feathery aggregatesof deep
red to bronzy plates, botryoidal aggregatesof shiny
black fibers, shiny black plates, and lustrous small
wedge-shaped
crystals.A spectacularspecimen,measuring 6 x 7 cm in area,showsthe mineral as broad
plates up to 5 mm across which are grouped as
bunchedradial aggregatesalong a fracture in a dense
rockbridgeite-ferrisickleritemass; its lustrous black
color is reminiscentof hematiteand manganitethough
it lacks their steel-greytint. Robertsitelines cavities
in rockbridgeite and ferrisicklerite upon which are
placed crystals of leucophosphite,jahnsite, and hureaulite. A late generation of this platy robertsite
often is deposited upon these minerals. Another
specimenshows a dense mass of deep red-brown
massive robertsite in which cavities are lined with
crystalsof the same.It is this
lustrouswedge-shaped
specimenfrom which crystalssuitablefor X-ray and
rnorphological study were obtained. All specimens
originatedfrom the Tip Top pegmatite.The mineral
also occurs at the Linwood pegmatitein a paragenesis similar to the Tip Top material, and in small
amounts at the White Elephant and Gap Lode pegmatites.
The color is shiny black, blood-red to reddishbrown in thin slivers, streak chocolatebrown, hardness3.5, cleavage{100} good. The specificgravity
of the crystalsis 3.17 (sink-float in methyleneiodideon botryoidal
toluene),3.13 (Bermanmicrobalance,
fibers). Finely fibrous material is silky, deep reddishbrown, resembling goethite. Thin plates are reminiscent of lepidocrocite.
Evidence provided here supports the statement
that robertsite,mitridatite, and arseniosideritebelong
to the same structure type. This is of considerable
interestsincemitridatite is a stableand persistentlow
temperature phase and occurs frequently as dullgreen stains coating wall rocks in pegmatiteswhich
carry transition metal phosphateminerals.
Crystal morphology
Work on the entire mitridatite problem has been
Single crystals of robertsite suitable for detailed
hindered through lack of suitable single crystal maand X-ray study are rather rare, and
morphological
occur
as
terial. All three phases characteristically
provided adequatematerial for
specimen
one
only
plates,
fine fibrous masses of thin curved
dense
analysisnow in progress.Meathe
crystal
structure
nodules,and stains.We shall elaborateon the crystal
thick
tabular and wedge-shaped;
surable
crystals
are
chemistry of the robertsite-mitridatite-arseniosiderite
pseudo-rhombohedral
in apvery
thick
are
crystals
group as a conclusionof this study.
THREE NEW TRANSITION METAL PHOSPHATES
pearance.Crystals range from 0.05 to 0.5 mm in
maximum dimension. They are frequently twinned
by rotation normal to {100} and often involve rotations by multiples of. */3 radians owing to the
pseudo-hexagonalcharacter of the crystal subcell.
Untwinnedcrystalsshowprominenta{100}, c{001}
and p{031}, and establishbeyonddoubt the monoclinic symmetry of the species.In addition several
doubly terminated crystals establishedthe monoclinic 2/m holosymmetry.A typical developmentis
shownin Figure 3.
55
of the most remarkable of Nature's mineralogical
legacy. In addition, Mr. Roberts maintains a continued interest in the minerals of the Black Hills
pegmatites,particularly the rarer $pecies,and his
compendious knowledge of minerals in general has
consisently provided many fine specimens for research.
The Mihidatite and Arseniosiderite Problems:
Isotypy with Robertsite
a. Mitidntite
X-ray crystallography
Mitridatite is a name applied to many colloidal
and
fine-grainedsubstanceswhich occur as nodules
Determination of the correct space group and
gumlike massesat numerous localities in the
and
unit cell parametersproved difficult owing to the
Kertch
and Taman peninsulasin the Soviet Union.
rarity of suitable single crystals. Despite the rather
The
most
recentstudy on the problem, an investigalustrous and even appearaoce of many crystals,
tion
mitridatites
by Chukhrov, Moleva, and
on
goniometric examination revealedtwinning by rotaprovides
powder and optical data.
(1958),
Ermllova
tion of + r/3 radianson {100}. X-ray photographs
A
firm
of
mitridatite
chemistry was
knowledge
the
of the same were almost impossible to decipher
until a small untwinned fragment was secured.
Rotation about [010], [001] and [00], and Weissenberg photographsof the h : O, I : 0, k : 0 to 4
c
q
levels, establishedthe monoclinic end-centeredcell
in Table 5. It exhibits a profound and persistent
substructurewhich obeysthe sameextinction criteria
and requiresb (sub) : b/3. After the b-axisrotation
photograph was prepared, successiverotation photographswere obtainedby regluingthe crystal ! r/3
radians aw4y from b. The three photographs,whose
axes are perpendiculat to a*, reveal a pronounced
pseudo-hexagonal
cell. However, only the b-direction
afforded evidence of a mirror plane although the
axial translationsare roughly of the samemagnitude
for all threephotographs.This conclusivelyestablished
the monoclinic character of the species.We note
that {3 6(sub) : 11.27A nv
".
A partly indexed powder pattern
appearsin Table
5. Sincethe chemicalanalysisand optical properties
shall be correlated with those of mitridatite and
arseniosiderite-as are the X-ray data-we provide
further discussion of the new speciesin the next
section.
A
B
Natne
The name robertsite was approved by the Commissionof New Minerals and Mineral Names,International Mineralogical Association. It is a privilege
to name this interestingspeciesafter Mr. Willard L.
Roberts,Mineralogist,SouthDakota Schoolof Mines
and Technology,in whose private cabinet are some
Frc. 3. Crystal of robertsite showing the forms c[001 1,
a{100}, and 4{031}. Tip Top pegmatite.A. Plan. B. Clinographic projection.
PAUL B. MOORE
StructureCell Data
Taur,r5. Robertsite,Mitridatite,and Arseniosiderite.
s,G[)
!6)
s6)
1 7. 3 6 ( 2 )
L 7" s 2 ( 2 )
1 7 . 7 6( ' { )
rs.s3(s)
l e . 3 s( 4 )
1 9" 5 3
1 r . 3 0( 3 )
11.30
B
96.0()
II " 2s(2)
(8)
9s.e20
I e6.o]
space group
A2/a
A2/a
lAz/a7
gravity
specific
density
(Em cm-31't
(oH)6 (Hzo)3[ Po4]4
ca3Mni+
?+
carFe[' (oH) (Hzo)3[ Poq]4
6
The density
I
*Robertsite.
is
Tip
2Mit"id.tit".
?
in
ideal
Top pegmatite.
White
-Arseniosj.derite"
Drrors
computed from
Elephant
formula
and t h e
From rotation
pegmatite.
ceII
I
data.
and Weissenberg data.
From r o t a t i o n ,
Mapimi, Mexico.
Fr-om partly
b and c are probably i 0.1 A.
?+
carFe[' (o]D6 (Hzo)'[Asoulu
8
I
*
3.59
3.08
3.05
formula
3"58,3.60
3.24
3.13,3.17
Weissenberg and precession
indexed powder data,
hindered by the lack of coarse-grainedmaterial,
in particular of singlecrystals.In this study, we offer
evidenceof specificstatusfor mitridatite and conclude
on the basis of powder diffraction patterns that the
material of Chukhrov et al is the fine-grainedequivalent of our specimensand that the materials are in
fact the samespecies.
Recently, Mr. W. L. Roberts provided the senior
author with some excellent crystals which afforded
powder patterns (Table 6) similar to robertsite and
practically identical to the powder data of Chukhrov
et al. ln addition, minerals D, E, and F from the
Borboremapegmatite,describedby Murdoch (1955),
appear to belong to the robertsite-mitridatiteseries.
The prominent powder lines are 8.65/10; 5.ffi/5;
and 2.74/6. The crystals, which line cavities in
massive material and which are associated with
jahnsite, collinsite, hydroxylapatite, and hureaulite,
were collectedon the dumps of the White Elephant
pegmatite,whose paragenesisclosely resemblesthat
of the Tip Top pegmatite suite. Single crystals are
thin tabularup to 0.2 mm and afforda{100},c{001}
(small), and rather commonly, ul423l. This last
form was firmly establishedon the basis of careful
X-ray alignment. Precessionphotographs with a*
horizontal on the films afforded the opportunity to
explore b- and c-axisprojectionsin detail. The single
crystal data in Table 5 thus derived clearly establish
matched with
data.
(1) and (2).
isotypy with robertsite, including similar sub- and
super-structurereflections.Like robertsite,the strong
substructure reflections predominate, resulting in
similar and relatively simple X-ray powder patterns.
Combinations of a{100} and ol423l result in a
polyhedron (Fig. a) with profound pseudo-rhombohedral appearance.
Mitridatite crystals are deep red to bronzy-red,
pleochroicpale yellow-greento red. Crushedcrystals
and fine-grainedmaterial are dull olive-green,as is
the streak, the latter aiding in distinction from robertsite whose streak is brown. The specific gravity
is 3.24 -+ 0.02, determinedby sink-float on single
crystals.
Mitridatite commonly occurs at the final stages
of corrosion of primary transition metal phosphates
in pegmatites.The dull green stains on silicates in
pegmatitesare in part mitridatite.
phosphate-bearing
Scrapings of such stains afford powder patterns
similar to coarsely crystalline mitridatite but with
considerableline broadening. These stains form at
low temperatureand coat large surfacesof pegmatite
exposuresafter they have been abandonedand exposed to weathering.The occurrencesat the Kertch
and Taman peninsulasare in sedimentaxyotilitic iron
ores.Vivianites, which occur as sedimentarynodules
derived from the decompositionof organic remains
as well as vivianitesfrom pegmatites,developin time
T'HREE NEW TR.ANSITION METAL PHOSPHATES
57
The "mazapilite" of Koenig (1889) was shown by
Foshag(1937) to be,arseniosiderite.
Through the help of Mr. John S. White, Jr., we
secureda specimenof the "mazapilite" and part of
the material describedby Foshag (1937). The powder data are identical for both and are offered in
Table 6 for Foshag'smaterial. The obviousrelationb. Arsmiosi.derite
ship with robertsite and mitridatite provided opThis species,long of uncertain status, occurs at portunity to derive approximate crystal cell data
many localities as a low,temperatureoxidation prod- (Table 5) by analogy with those minerals. Koenig
uct of liillingite and arsenopyrite.In addition, it re- (1889) obtained a specific gravity of 3.58 for
places earlier arsenatessuch as scorodite. Palache, "mazapilite," and Mrose in Palacheet aI (1951)
Berman,and Frondel (1951) list it as hexagonalor obtained3.60.
tetragonal,basedon optical data. The color is golden
yellow in fine massesto reddish-brownin fibers to c. Optical data lor robertsite, mitidatite, and
deepreddish or brownish black in granular material. arseniosiderite
It is extremelydichroic reddish-brownto practically
New optical data for robertsiteand mitridatite plus
(1934).
colorless,accordingto Larsen and Berman
the data in Larsen and Berman (1934) for arsenio-
a film of mitridatite, suggestingthat ground waters
provide Ca2* cations for its formation. Mitridatite
may prove to be a potentially important phasein the
chemistry of soils. Despite the complexity of its
crystal cell, we are approachingthe problem of the
crystal structure with enthusiasm.
TrsI.r 6. Robertsite, Mitridatite, and Arseniosiderite.X-ray Powder Data
MITMDATITE
ROBERTSITD
q(obs)
I/1.
hkJ.
d(calc)
200
03I
+ . 3 2 500
4.13 3 3 I
8.63
8.63
5
5.61
5.63
1
+.32
4.1|+
2
3.f+8
rt
3.27
t0
z
z
)
?uol
z
4.11)
+
2.213
L
2
2.137
r.89r
2.90
2
2.88
2
Z.LO6
I
2.068
r.899
3
2
tl
r.901
r.7+L
1.612
I
3
2
2
f.588
1.5+8
1
600
? te
2.88r
2.765
L
z.tfz
2.048
I.5ttz
l. r+64
I. +I2
Ii3
2.945
2.760
c
Iq
4
2.207
2.169
I
3.2t1
?
t
233
2 . 8 7 7 600
2.809 004
2 . 8 0 3 162
3
r+
1.585
3.22
2.94s
o
3.O2
2
I
t+
3.48
2
2 . 2 + 9 40q
2 . r 5 8 800
f.745
r.623
402
r
3 . 0 2.
2.72L
2.617
2.562
2.460
5
2
3.3I
3 .1+9
3.01
7
I
t+
2.L60
3.28
2
L
2 . 7 5 8 2o+
2 . 7 5 7 162
2 . 5 8 4 362
2.+59 602
2.r+65
2.223
4
8.8I
2.772
2.622
2.602
2t937
2.876
2
200
7
I
8
3
I
2
L
3
t
2.590
8.83
5.63
4.54
160
260
3.0+
2.952
+
8" 8 q
5.62
rr.58
4.30
3.+9
3.20
)
6
2 q6
I
2.+6
rr
6
2
cffiera
2.522
r
1 nq7
I
L.797
5
Z.L7
2
L.770
2.10
3
2.10
4bd
l.6r+3
+ 20 lines,
3
7
l.9rt
1.750
1.616
1.553
I.t+7+
1.q08
dianeter,
2.57
2.+6
1.415
Fe&
radiation,
correeted
for
4
2
7
l.9l-9
L.7t+5
1.614
3
2
1.555
1.r+83
r
r.+15
r
1?06
1
1 _772
shrinkage.)
03r
202
060
2.18
?7q
(II4.6m
2.73
r0
7?
hkl
I0
5
3
5
033
J_
4
d(catc)
I,/I"
8.60
5.60
iaa
3.03
2.7+9
d(obs)
d(obs)
6
8
I,zIo
3.2+
J.ZU
2
3
8.64
5.55
ARSENIOSIDERITE (MAPiMi)
4u
3.Lt
6
L0
6
3
d(obs)
MTTRIDATITE (SAmpIE 3)
(Chukhrov et a1., 1958)
3.52
3. 2 5
2
I
2.807
I,zI.
MITRTDATITE (Sffiple 2)
(Chuldrov g 4.,
1958)
d(obs)
I,/Io
<2.
20tl
58
PAUL B. MOORE
d. Chemistry of robertsite, mitridatite, and
arseniosiderite
We submit two new chemicalanalyses,for robertsite fibers in associationwith singlecrystalsfrom the
Tip Top pegmatite and for massivedull green mitridatite closely associatedwith crystals from the
White Elephant pegmatite. Both afforded powder
patternswhich are identical with thosefrom crushed
single crystals. The massivegreen mitridatite contained a substantial admixture of quartz which
evidently crystallized at low temperatureand which
@curs as very small grains in the mass. These
Ftc. 4, Pseudo-rhombohedralcrystal of mitridatite resulting
from the forms a { 100} and ul42ll. White Elephant pegmatite. analyses,along with analysesfor two rather coarsegrainedarseniosiderites
reportedby Koenig (1889)
Clinographic projection.
(: "mazapilite") and Foshag (1937) appear in
siderite and those of Chukhrov et al f.or mitridatite Table 8. Ten analysesfor mitridatite from the Soviet
are listed in Table 7. We also provide Gladstone- Union appear as a compilation from severalsources
Dale calculationsfor all three compoundsand note in Palacheet al (1951). Sinceall specimens
were of
the excellent agreement with the o'bservedmean a fine-grained and colloidal nature, they contain
indices of refraction.
varying amountsof water, a deficiencyof CaO, and
All three compounds are optically very similar; an excessof Fe2O3,suggestingmitridatite-goethitethey are strongly birefringent, strongly absorbingin hematite admixtures.Chukhrov et al (1958) offer
the Y and Z directions, biaxial negative, and with five new analyses,all rather similar. We provide a list
small 2V. The acute bisectrix is roughly pelpen- of the analysesof samples 2 and 3 in Table 8.
dicular to the planeof the good { 1@} cleavage.The They proposethe formula CazFeg( POo) s- ( OH ) *-r,'
data of Chukhrov et al (1958) show significantly nH2O. Their study leaves little doubt that our
lower indices, doubtless arising from the highly coarselycrystalline material is the samespeciesand
hydrated nature of their fine-grainedmaterial.
that the deviationsin chemicalanalysis,specificgravTenls 7. Robertsite, Mitridatite, and Arseniosiderite.Optical Data
(n> obs
(n> caLc*
L . 7 7 s( s )
1.82 (1)
1.805
1.803
1 . 7 8 s( 5 )
1.85 (1)
1.828
1.835
2v
t8o
t:10'
absorption
YrZ >> X
YrZ >> X
Y,Z >> X
pleochroisrn
Y,Z deep reddlsh brown
X pale reddish-plnk
YrZ deep green1sh brown
X pale greenish yellow
Y,Z dark reddlsh-brown
X colorless
orlentatlon
x nearly ! {roo} x nearty ! {roo}
B,Y
L.762
L.770
1.80
1.88
1.815
1.898
1.870
1.853
uniaxlal
slgn
x ! {roo}
lRobertslte.
Ttp Top pegrnatite.
zMltridatlte.
Whlte Elephant pegnatlte.
3Mltridatit..
(Sarqple 2).
Fine-grattred *aieital
Chukhrov et aL (L958).
qArsenioslderite.
Larsen and Berman (1934).
They noEe X = c and perfect
5ArsenlosiderLte.
Larsen and Berman (1934) for tire varlety
"nazapilite"
*Fron Gladstone-Dale
relationship
for
ldea1 fornulae.
YrZ >> X
{001} cleavage.
THREE NEW TRANSITION METAL
PHOSPHATES
59
ity, and optical propertiesresultfrom the fine-grained
Specimensof the type materialsfor all three new
nature of their material. In addition, three analyses specieswill be depositedin the U.S. National Muon fine-grainedarseniosideriteare compiled in Pal- seum.
acheet al (1951), but their statusin the absenceof
Acknowledgments
X-ray patterns is uncertain. Thus, discussionsof
probe
The
electron
analyses on jahnsite and segelerite,
them would be of questionablevalue.
requiring cgreful preparation and choice of standards, were
Our two analyseswere computedinto cationsper
conducted by Mr. T. Solberg. Dr. A. J. Irving kindly
unit cell utilizing the specific gravity averagesand contributed to the study when the crystal-chemicalrelationthe cell volumesfrom the X-ray studies.The best ship betweEn overite and segelerite was recognized. Conagreement,which also agreesremarkably well with tributions bf fragments of type materials from the U.S.
the arseniosiderite
analyses,suggestsideal Ca3Mn8.a National Nfuseum were invaluable in providing results on
be confounded. Messrs. W. L.
(OH)6(HrO)r[POn]n,with Z: 8 for robertsiteand species wh.flch could easily
Roberts anil C. Segeler provided samples of many fine speciobvious isotypy among all three species.We note mens for riesearch.
that the massivemitridatitesrevealan excessof water
This woi'k was supported by the NSF grant GA 10932-Al
which is repeatedconsistentlyin the other analyses awardedto P.B.M. and NSF-MRL support to The University
for colloform materials.and subrnit that this excess of Chicago.
is adsorbedand not a part of the crystal structure.
References
In all analyses,the Ca2*content is low by about 5
CuuxHnovJ F. V., Y. A. Morrve, eNo L. P. Enrvrnove
to 10 percent.This may resultfrom slightexcesses
of
(1958) New data concerning mitridatite. Akad. Nauk
trivalent cationsand/or alkaliesas substituentsfor
S.S.S.R. Ser. Geol. No. 8, 16-26 (translated from the
Russian).
Ca2., but more likely arises from partial vacancies
FosHAc,
W. F. (1937) Carminite and associatedminerals
over the large cation sites. Based on the ideal forfrom Mapimi, Mexico. Am. Mineral. 22, 479-484.
mulae, the computed densitiesare low by about 5 KoENIG, G. A. (1889) VI. Neue amerikanischeMineralpercent and suggestthat the slight excessesof trivavorkommen. 1. Mazapilit. Z. Kristallogr. 17' 85-88.
lent cations are real. A better fit can be obtained Lenssx, E. S. III (1940) Overite and montgomeryite: two
new minerals from Fairfield, Utah. Am. Mineral. 25,
(OH) ru(H:O)slPOilr, Z
with the formula Ca6Fe3.e
315-326.
= 4, but we doubt whether the preciseformula can
,lNo H. BBnueN (1934) The microscopic determibe unambiguouslystated without knowledge of the
nation of the nonopaque minerals, 2nd ed. U.S. Geol.
crystal structure. Accordingly, the simpler formulae
Suru. Bull. E48, 31.
are proposedin this study.
Moonn, P. B. (1970) Structural hierarchiesamong minerals
containing octahedrally coordinating oxygen. l. StereoThe agreementbetweenthe chemicalanalyses,the
isomerism among corner-sharing octahedral and tetraX-ray powder data, and the opticaldata leaveslittle
hedral chains. Neues. lahrb. Mineral. Monatsh, 1970,
doubt that the three speciesrobertsite,mitridatite,
163-173.
and arseniosiderite
belongto the samestructuretype. (1973) Pegmatite phosphates: mineralogy and
In addition, it is very likely that CagMns.r(OH)e
crystal chemistry. Mlneral. Rec. 4, 103-130.
(FLO)a[AsO+]rwill prove to be a stablephaseand MnosE, M. E. (1955) Problems of the iron-manganese
phosphates.Geol. Soc. Am. 1955 Program Abstr., 764.
may exist in Nature.
Munoocn, J. (1955) Phosphateminerals of the Borborema
We concludeby proposingthe following formulae:
pegmatites: I-Patrimonio. Am. Mineral. 40' 50-63.
*
nlOH)s(Hro)3 [ po4]4
robertsite
Ca, Mn'
mitridatite
ca, Fe"n(oH)6(Hro)s
arseniosiderite
CarFe'*nlOH)e(Ftrro).[AsOr]r.
I po4]4
Perecnr,, C., H. BrnIvrAN,AND C. FnoNpEr (1951) The
System of Mineralo'gy of Dana, Yol. 2, Seventh ed., John
Wiley and Sons,Inc., New York, pp. 955-956.
Manuscript receioed, JuIy 23, 1973; accepted lor
publication, August 30, 1973'