IN REPLY REFER TO:

UNITED STATESDEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEYWASHINGTON 25. D. C.

18 1954

AEC-1103A

Mr, Jesse C. Johnson, DirectorBiyision of Rav MaterialsIT. S» Atomic Energy Commissionl6th St* and Constitution Avenue, H.¥*Washington 25, B. C.

Bear Jesse;

Transmitted herewith are three copies of TEI-^59* "Ifantroseite

and paramontroseite^" "by Howard T. Evans, Jr*, and Kary E. Krose, June

We are asking Mr. Hosted to approve our plan to submit this

report for publication in American Mineralogist.

Sincerely yours,

. H 0 Bradley Chief Geologist

JAN 22 200! 7 JUN 198"

Geology and Mineralogy

By

Howard T* Evans, Jr«, and Mary E. Mrose

June

TMs preliminary report is distributed vithout editorial and technical reirieir for conformity -with official standards and nomenclature. It is not for publicinspection or quotation*

report concerns work dene on "behalf of the Bivlsion of Ea-w Materials of the U* S. Atomic Energy Commission.

USGS - TEI4-39

GEOLOGY AND MINERALOGY

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CONTENTS

Page

JT1.O13 wJTcLC, \j 9^v«*9Q«»*«09D**#e6$»a$&*<»90*ofr»00a»«?0feo0*09«oaat****» '

Introduction ••.. a « v .»«.*.«*» A .,«.«..o.•»•»«••.o*»»»««***«»»v*» 5Source of the data aft«.«o»*««a»»»»»*»».»*»»•»•*»..•••••*»•••,*« 6Determination of the crystal structure of paramontroseite 0 , 9 o. 7 Refinement of the montroseite and paramontroseite structuresby the method of least squares ,.•,.,.•,«.•.••.,.•••••».o.*.« 8

Structural features of montroseite and paramontroseite e .*.««.* 10Solid state alteration of montroseite ,*»»«.*•••«•,o.o»»»»»«o.» 11Other examples of solid state alteration phenomena ,<,* 0 **»<,**<,» 13Summary » 0 ..,«.eoo« 0 »o,oaao<f <.eooi,oo»<> »«r««i,«»<. 0 ». *.»*,»«. *«•«•••»»« 15» ™ T •> V •• unawirvvwirv o «• ~ » ^

Heferences * ooeo, 00 oeoa*»o»»«»»<> 0 <.oi>»<.»«.«<>» 0 «*»»»»»«.»«#»«»*9»»»« 1"

ILLUSTRATIOHS

Figure 1» Buerger precession photograph of the (Oki) net plane of the montroseite crystal, showing sharp and diffuse spots „„.»*....*...*.»..»«„•*..».»...••. 2^

2. Electron density projections along the £ axis of(a) montroseite and (b) paramontroseite «>„.,.«,«,*.,„<, 25

5 e Interatomic distance rectors in montroseite andparamontroseite »»...«•..•.*,...«...•*.«,»•».»•»*»»• 26

^• 0 Yiew of crystal structures along the £ axis of (a)montroseite and (b) paramontroseite o».»**«.•*,«»*«« 27

TABLES

Page

Table 1. Lattice data for montroseite phases »«*„.*»»<.„.«».«.» 17 2, Least squares-^determined parameters and standard

errors for montroseite and paramontroseite «>„«.*.«.» 18 3* Observed and calculated structure factors for

montroseite and paramontroseite » ao ,o*....»••»•*•«»«» 194. Interatomic distances in m&ntroseite and para­

montroseite »ooo»e*«»««<><.».«<..».<>«>*.»*<>«*«*«•»»«»•** 265. Standard errors of atomic positions in montroseite

and paramontroseite „««»»,,,#«.«,»«<>•.•*„»»»....«»..*, 23

MOMKOSEITE A303 PARAMOUimOSEITE

By Howard T. Evans, Jr?, and Mary E. Mrose

ABSTBACT

Montroseite (Y,Fe)0(QH), has been shorn "by ETans and Block

to hare a structure analogous to that of diaspore, AIO(OE). Altered

crystals of montroseite give Multiple X-ray patterns, showing one sharp

orthorhombic lattice corresponding to the host crystal, and two diffuse

lattices of similar symmetry and dimensions in parallel orientation. The

sore prominent of the diffuse phases is interpreted as a metastable form

of V02 , resulting from the oxidation of the host crystal, and is given

the name "paramontroseite". Paramontroseite has sa - 4,89, fc * 9«-39>

£ * 2,93 A, space group Fbnsu Complete refinement of the structure of "both

montroseite and paramontroseite has "been carried out "by electron density

synthesis and least squares analysis. The outstanding difference between

the two structures lies in the length of the oxygen-oxygen distance corre­

sponding to the hydrogen "bond in laontroseite. This length increases from

2,63 to 3*87 A in going from montroseite to parauontroseite, indicating the

loss of hydrogen during the alteration* The concept of an alteration process

involving a migration of ions and electrons through an unbroken oxygen

framework is thus directly supported by the crystal structure analyses, and

also by other X-ray diffmction and chemical information* The postulated

alteration laeehanism is illustrated by certain other examples, notably the

alteration of lepidocrocite and isagnetite to maghemite, and go^thite to

hematite.

In a recent communication, by Weeks, Disney, and Sherwood (1953)?

the discovery, properties, and mode of occurrence of a new mineral from

the Colorado Plateaus region, montroseite, were described.. The material

forms submetallie, greyish-black bladed crystalline Bosses * In cavities

it forms sioal.1 lathlike crystals with a perfect (010) cleavage 0 The

density was measured on one sample as k 0QQ a The essential constitution

of montroselte was demonstrated, by means of a detailed crystal structure

analysis by Evans and Block (1953)* "to consist of a vanadium oxide

hydrate with the basic formula YO(OH), analogous to diaspore, A10(OH) 0

These authors pointed out that diffraction patterns obtained from appar­

ently single crystals of montroseite are multiple, showing the presence of

at least three phases» The multiple diffraction patterns show three ortho-

rhombic lattices in parallel position, with slightly varying lattice

constants, one characterized by sharp diffraction spots, the other two by

diffuse spot So Figure 1 shows part of a Buerger precession photograph of

the (OkjL) plane on which the sharp and the "diffuse B" lattices are clearly

visible 0 The data given for these lattices by Evans and Block are repro­

duced in table 1»

It -was tentatively suggested by Evans and Block that the sharp lattice

(for which the structure analysis was carried out) represents the original

host phase which subsequently alters by atmospheric action to give rise to

the diffuse phases* Hew information has now been obtained concerning this

alteration process as a result of a complete structure analysis of the

"diffuse B" phase, which is described in this paper „ The evidence is

sufficient to define the chemical nature of the "diffuse B" phase, and

establish it as a new mineral species 0 Therefore, because of the para-

morphic relationship that it has to the host mineral montroseite, as

described more fully below, -we propose far the "diffuse B" phase the name

paramontroseite 0

As a result of the study described herein, it has been possible to

show by the direct methods of X-ray diffraction and crystal structure

analysis that the naturally occurring crystals of the mineral are actually

in part or wholly pseudomorphs of the new mineral, paramontroseite, after

the original montroseite 0 The anomalous and variable results of chemical

analysis are fully explained-and, further, the mechanism of alteration by

oxidation and dehydrogenation is revealed*

SOURCE OF THE DATA

Crystals of montroseite from the Bitter Creek mine, Paradox Valley,

Colo 0 p were used for the structure investigations fl The first crystal to be

photographed showed all three phases present—the montroseite and para­

montroseite lattices being about equally intense, the "diffuse A" lattice

much weaker „ The. spots were streaked in a manner to indicate a distortion

of the crystal around the £ axis of 10 degrees or more, a habit which is

apparently characteristic of montroseite crystals» The intensity data for

montroseite were measured by visual estimates of 99 observed (hkO) reflec­

tions from this crystal registered on a ¥eissenberg pattern using M0K&

radiation, as described by Evans and Block (1953)* A second altered crystal

of montroseite gave a nearly pure paramontroseite pattern, with only slight

traces of the strongest reflections of the montroseite lattice still dis­

cernible » This crystal was used to measure Jk- observed (hkO) reflections

by visual estimates mads on a ¥eissenberg pattern made with CuK& radiation,,

Ho corrections were made for absorption•

7

Despite the distortions inherent in the crystals, the data for

montroseite give excellent agreement -with those calculated for the pro­

posed structure, but those for the diffuse phase are of very poor quality•

Both sets of data have been treated by the method of least squares as

described below, in order to ensure the determination of the most likely

structures and at the same time derive the standard errors appropriate

to eacho

DETERMINATION OF THE CRYSTAL STRUCTURE OF PARAMQHTROSEITE

The distribution of intensity among the (hkO) reflections for para-

montroseite is quite similar to, though differing markedly in detail from,

that of montroseite as reported by Evans and Block (1953)« (See table 3?

p. 19») On the assumption that the paramontroseite structure is similar

to that of montroseitey the Fatterson projection along [pOlJ was partly

computed in order to locate the V-V interatomic distance rectors * Peaks

were found near the expected positions, and from them vanadium parameters

were obtained from -which the first set of structure factors -were calculated

(oxygen atoms omitted)„ These structure factors for vanadium yielded

probable Fourier phases for the 5^ observed (hkO) terms, permitting the

synthesis of the electron density projected along the £ axis* Peaks

corresponding to oxygen atoms were clearly apparent in this map, and the

second set of calculated structure factors included all atoms in the cell,

with coordinates read from the electron density map 0 The usual electron

density, synthesis=structure factor cycle was repeated twice more, until the

map coordinates were consistent with all the phases „ The final electron

density projection is shown in figure 2b« Figure 2a shows the corresponding

electron density projection of montroseite from Evans and Block (1953)

comparison The atom coordinates as measured from these amps by

8

parabolic interpolation are given in ta"ble 2.

KEFOTSMEIT OF THE MOHTRQSEHE AID FARAMQNTROSEITE STRUCTURES

BY THE METHOD OF LEAST SQUAKES

Because of the distortions in the electron density maps caused by

inaccuracies In the intensity measurements and series termination effects,

the method of least squares -was used to derive the most likely structure

consistent with the original data. The method was applied in a straight­

forward manner as described in seTeral other places, (See, for example ,

Shoemaker, Donahus, Schomaker, and Corey, 1950*) The analysis is "based

on the structure factor function

where B is the temperature coefficients s = (sin 0)A, f . is the scattering fac-- ~ ~1

tor for the atom J, and x., y. are z are coordinates of each atom jo TheB*fc' ——I * X. "I —— .J! <A>

M. M. «i

parameters to "be determined are x(v), j(Y)j 2s(0-r)y ^(OT)? ^(OTT)?

), and Bo As all atoms are well separated in the £ axis projection^

all nondiagonal terms in the normal equations were neglected. The only

matter of judgment concerns the manner in which the observations should be

weighted in deriTing the normal equations. Using these considerations, the

normal equations reduce to a series of independent linear equations in

terms of correction terms AX, to be applied to each of the structure

parameters :

where AF = (iWhc - 1*^1^)? x is the structure parameter x(V), y(V), x(0T ),«"•"*• uf^xp-Kf O ^^!JB»€** JL, » »*w "•*•• *•* ••* * *•

etc . , and Vw is the weight giren to each observation* If intensity as

measured is a logarithmic function of film density in which errors of

estimate by the eye are assumed to be distributed normally, it can easily

be shown that the appropriate weighting factor is

Although experience seems to show that such an assumption is somewhere near

the truth , the point is controversial, and we hare carried out analyses with

both

- I= — - (weighted) and

= 1 (unweighted) «,

¥e accept the structures derired from the weighted analysis as the best ?

but it is obs erred that the difference between the weighted and unweighted

results is generally less than the calculated standard errors « The standard

error of Is is

«, .-

where n is the number of observations (99 for montroseite , 3^ for para-

nwntroseite ) and ̂ the number of parameters (7* including the temperature

factor? B) o The standard error of x s £ , is giyen by»eC

f *= 4 _"2 T* fd?\*2Tw(%)

The AF values vere obtained lay scaling F. by multiplying by

, Zl

for unweighted calculations, and

k = J- 5;for weighted calculations* Actually^, the ^alue of k is not Tery critical^

except in the case of the weighted calculations of AB for the temperature

corrections j where it was found necessary to take account of the cross-

10

product terms between ^B and k.

The results of all calculations for both montroseite and para-

montrQseite are given in table 2 0 The final parameters for montroseite

and paramontroseite used to determine bond lengths in the following section

are those listed under the columns labeled "weighted" in this table,

The reliability factor

obtained with

k = 2 \E&*\has a -value R = Q<,113 for 99 observed reflections for montroseite 9 and

H = Q a2k for 5^ non-zero reflections for paramontroseite^ Observed and

calculated structure factors for montroseite and paramontroseite are listed

in table 3*»

STRUCTURAL HEATUR1S OP MOSTROSEITE AED PARAMOMKOSBITE

The interatomic distances defined in figure 3 are tabulated for both

structures in table k» The standard errors of the lengths shown are

derived from those associated with the parameters given in table 2* It is

found that the errors in location of most atoms are practically isotropic,

and have magnitudes shown in table 5- Errors on interatomic distances T

between atoms A and B are given by;

g r - ^ + *?

f twhere c T is the error of lattice measurement in percent

^Because of an error made in the calculations, the values of F , for reflections with k odd in table 2 of the paper by Evans and Bloct ft (19535 are incorrect,"" This error does not affect any other data given in that paper 5 except that E - 0 0 11 instead of 0,21.

11

It is clear that the essential principles of coordination and

vanadium-oxygen bonding are the same in both montroseite and paramontrose-

ite* The main difference between these structures, as shown by the £ axis

elevations shorn in figure k, lies in the fact that the zig-zag octahedron

chains have rotated some 28 degrees around the £ axis direction in passing

from one to the other « This process has been accompanied by tw important

changes in the structure %

(1) First and most important, the interoxygen distance, H, is short

(2 063 A) in montroseite, but very long (3»8? A) in paramontroseite „ The

former Yalue is very reasonable for a hydrogen bond, as suggested by Svans

and Block (1953)? "but the latter is far too large for such a bond. As

there is no other logical place for hydrogen in the structure, the conclusion

must be drawn that hydrogen is absent in paramontroseite,

(2) Second;, the vanadium-oxygen distances are slightly, but probably

significantly shorter in paramontroseite than in montroseite 0 The change

is close to that which would be expected when one electron pair is added to

the montrosiete vanadium bond coordination system j i^e,,, when vanadium is

oxidized from +3 to +k through the loss of hydrogen,

SOLID STATE ALTERATION OF MQBTROSEM

In light of the known factSj the history of the mineral montroseite

may be outlined as follows s

(a) The mineral montroseite, YO(OH) ; (with some Fe usually

replacing V).ls deposited in crystalline masses, by an unknown process, in

the sandstone matrix 0

(b) The crystallized montroseite is oxidized by oxygen in the

atmosphere or in ground water to paramontroseite, at temperatures below

50° C, according to the reactions

2TO(OH) 4-(Montroseite ) (Paramontroseite )

12

(c) The oxidation process is accomplished by a migration of

the hydrogen atoms through the aontroseite crystal structure to the

crystal surface where they combine with oxygen* The close-packed oxygen

framework is slightly shifted in this process but is not broken down,

The process may pass through an intermediate stage involving ,;bhe "diffuse A"

phase»

(d) The end product of this solid state alteration process,

paramontroseite, is itself unstable, and is subsequently destroyed by

weathering action and replaced by the eorvusite type of minerals.

These conclusions are drawn from the following established facts;

I., The montroseite phase gives rise to a sharp diffraction pattern,

suggesting normal crystal growth of a primary phase*

2« The paramontroseite diffraction pattern is diffuse, su^esting

that this phase occurs as alteration nueleii finely disseminated through

the host crystal, as would be expected to result from the postulated

diffusion of hydrogen atoms,

3« The structure of montroseite and paramontroseite, especially the

nearly hexagonal close-packed oxygen framework, is the same*

k» The crystal lattices of montroseite and paramontroseite are in

parallel position„

5= The average temperature ribration amplitude far montroseite

(= 'yB/Sft 2 ) is 0*21 A indicating a firmly bound, stable structure, whereas

the average amplitude of paramontroseite is 0,53 A indicating a much less

stable structure. The difference in temperature vibration accounts for the

much larger and more diffuse appearance of the vanadium atoms in the

electron density map of paramontroseite as compared with montroseite (fig* 2)*

6* The hydrogen bond length of montroseite has greatly increased

in paramontroseite, indicating loss of hydrogen?

13

7=. The vanadium-oxygen distances in montroseite are longer than

in paraiaontroseite^ indicating oxi«3ation of the vanadium,,

8 9 The powder patterns of montroseite can "be indexed on a lattice

•which conforms most closely with the paramotroseite lattice (Weeks ,

Cisaey^ and Sherwood^, 1953)" Actually , calculated and observed inter-

planar spacings show fair agreement, using lattice parameters inter­

mediate between the "diffuse A" and "B" lattices.

9* Chemical analyses (Wee&Sj, Cisney 9 and Sherwood, 1953) show exten­

sive 5 in some cases nearly complete , replacement of YgOs by YgO^o Also*

the water content is decreased consistently with the oxidation of ¥0(OH)

to V02 «,

It has been mentioned that there is evidence for a third phase present

in montroseite crystals , referred to as the "diffuse A" phase „ The true

nature of the "diffuse A" phase is unknown,, Its relation to the montroseite

and parauontroseite suggests that it may represent an intermediate step in

the alteration of one into the other. If this is the case ? the "diffuse A"

2 7 phase may be V^OaCOH)^ having the space group Fb2_m (C~ ) or KLam (C_ ),

—— -L~~ <=•*[ ~ 1 — — £^T

with 2 formula units per cell* This non-centrosyua^tric phase would corre­

spond to the montroseite structure with half the hydrogen atoms removed*

Alternatively , the "diffuse A" phase may represent some sort of separated

Fe-rich phase , but its constants are not the as those of goethite 0

EXAMPLES OF SOLID STATE ALTEEATIOH IHE10MEMA

It is well toown that the cubic polyuorph of Fe^Os can be prepared by

warming isagnetite (Fe304) in a stream of oxygen at low temperatures « 2^0 C)

At higher temperatures the cubic /-Fe-gOa is converted to the rhoffibohedral

Ik

a-Fe203<> It is understood that the oxidation occurs without disturbing

the cubic close-packed oxygen framework of the spinel structure of magnetite

The oxygen lattice grows at the crystal surface, and the Fe atoms diffuse

outward until the spinel-type unit cell contents Fe^Oss is reduced to

Fe ,0 » Evidently, 7~Fe2Q3 is wholly metastable, and can only exist as21S- 32

t3

a result of a low temperature chemical change in the solid state from a

stable phase 0

This phenomenon probably accounts for the observation by Newhouse (1929)?

that magnetite crystals from Magnet Cove, Ark,, are coated with an oriented

over-growth of maghemite (7-FejgOs), Maghemite also is known (Sosman and

Posnjakj, 1925) as an alteration product of lepidoeroeite, FeO(OH), which has

a structure based on a cubic close-packed oxygen lattice, whereas hematite

(a-FegOa) is a common alteration product of goethite, which has the diaspore

structure like montroseite « These two examples do not involve oxidation but

the alteration process is probably similar to that of montroseite and

magnetite „

Artificial vanadium dioxide does not have the paramontroseite structure,

but rather a distorted rutile structure (Andersson, 1953)° Paramontroseite

is probably also metastable like maghemite , and can only exist through

solid state alteration from the stable montroseite at low temperatures ,

These minerals are most nearly analogous to groutite (JtoO(OH)) and

ramsdellite (MhO^), both having the diaspore structure, but unfortunately

there has been no study yet of the paragenetic relationships of the two

manganese minerals which would enable us to compare our conclusions regard­

ing the vanadium minerals 0

SUMMARY

The crystal structures of Bsontroseite, VQ(QH)^and paramontroseite,

V02 , hav£ been refined by the method of least squares. Both are based

on the diaspore structure type. Montroseite crystals give multiple

X-ray diffraction patterns, a sharp pattern -which has yielded the data

for montroseite, and a diffuse pattern which gave the data for para-

sjontroseite. An outstanding difference between the two phases revealed

by the structure analysis is that a hydrogen bond which is present in

montroseite is absent in paramontroseite. Thus, the chemical nature of

the two phases is confirmed and paramontroseite is established as a new

species „ In addition the paramorphic relationship between the two is

well escplainedo

Crystal structure data, lattice studies, certain diffraction -

phenomena, and chemical data have all led to the conclusion that montrose-

ite alters to pammontroseite through weathering action, by means of a

solid state reaction at lew temperature. This process involves the

migration of hydrogen atoms through an unchanged hescagonal close-packed

oxygen framework. Paramontroseite is evidently a metastable phase. The

alteration of montroseite to paramontroseite is apparently analogous with

that of magnetite to maghemite, lepidocrocite to maghemite, and goethite

to hematite,,

16

REFERENCES

AncLerssorLj, G*> ? 1953? X-ray studies on Yanadium oxides s Research, Y» 6,

Evans, H» T», Jr a , and Block , S» s 1953* The crystal structure of sontrose- ite, a vanadium member of the diaspore group: Am« Mineralogist,

NeirhQnse ? ¥ 0 H os 1929, The ifleatity and genesis of loadstone magnetite Icon. Geology , Y* 2k 9 p 0 62«6T 9

Snoemaker, ^ P 05 Donaliue, J W5 Bchomaker, Y., and Corey, R« B. ? 1950#Tke crystal structure of Ls-threonine , Am« Ckem* Soc. Jour»j Y<, T

R* B. ? and Posnjakj E- 5 1925 , Ferromagnetic ferric oxide, artificial and naturals Washington Aead. Sci* Jour«, v. 15?

Weeks , A* D 0? Cisney ? E« 3 and Sherwood, A* M», 1953? Mootroselte , a new Yanadium oxide from the Colorado Plateaus; Am« Mineralogist, r« 3

IT

Table 1.—Lattice data f,or montroseite phases

Formula

a (A)

b (A)

£ (A)

V (A3 )

d (calc. for 8$ FeO)

Z (formula units)

Space group

Montroseite "Diffuse A"

YO(OH) Vg03 (OH)(?)

4*54 4.80

9*97 9«&3

3 .-03 2,93

136.9 135*4

*.ll 4.15

k 2

Fbnm Pb^m (?)16 2.

Paraaoatros eite "Diffuse BM

V02

4.89

9*39

2*93

134 A

4a8

4

Pbnm

<D£>

Tabl

e 2o—Least a

qtaares-determined par

amet

ers

and standard errors

for

mont

rose

ite

and

paramontroseite

0

Par*

3V yv ^i

yoi

XO

IIyo

u

B

Mbn

tros

eite

Ble

cc

dens

*

~OoQ

510*

1^5

0^29

7-0

.197

-001

9T

-Oo0

51

Ua~

wei

^ite

d P

aram

eter

£

-0*0

511

Oo0

0086

0,

1^57

0,

0003

5

0*30

0 0

0003

^ -0

^201

0.

0016

-0»1

99

0,00

30

-0.0

53

0»00

l6

OA

9 0*

033

Wei

ghte

d*

Par

amet

er

£ •

-060

51?

0*00

054

oa1^

0.00

01.9

0*50

1 0*

0021

-0

.197

OoO

Oll

-0*1

98

0.0

02

1

-Q00

54

0.0

01

1

0«32

O

.C^-

1

Par

aiao

atro

se it

e

Ele

c0

dens

0

0.09

1}-0

01^5

0.12

7-Q

a243

-0,2

52-0

«0

12

Unw

eigh

ted

Par

amet

er

£

0«09

1 0,

00^8

Oal1^

0^0027

000

91

0,01

7^

-Oo2

5^

0.00

99

-002

31

0,01

97

-0*0

18

0*00

97

2.12

0.

398

Wei

ghte

d P

aram

eter

6

0,08

8 0*

003^

0*

1^3

QoO

Q15

Oal0

6

OcO

l8l

-0.2

35

0*00

5^

-0»2

27

0,01

57

-000

15

0,00

39

2 A

2 0»

867

reflection (9

70)

has been omitted from th

is a

naly

sis

because

of i

ts disproportionately h

igh, wei

ghti

ngf act

or

19

Table 3»-"- Obserred and calculated struetiare factors for montroseite and paramontroseite»

hkl

0200400600800,10,00,12,00,14,0O s l6 9 00,18,00 ?20 y O

no120130l4o1501601701801901,10,01,11,01,12,01,13,01,14,01,15,01,16,01,17,01,18,01,19,01,20,01,21,0

2002102202302402502602702802902,10,0

Moatroseite Sobs

18<>942 0232.35.127.49=6

28,6

12,614..6

56,233o953 .952 0214*09o6

42,2

11.8

28.0

17.7

11,411.817*3

13^8

19 »314 o411*212 a 652,638,424 o-25*9

25 0620«621 eO

•pi-ealc

~19 o 5-46 0 Q36.65=6

-34 0 8-10.72J 06

- 4*3-15,618*7

51o722 0 2-48*9-44,6-13,2-11.943 0 11-9

-15-72,6

-29 oO- 1.019^71.58A

13 «2-15-5- 2*31.7

- 4 0212,7

17=719*0

""JLjL o j

9*8-42,8»35.823 .8

- 6 0228 022^.5-25,5

Paramontrose ite Zobs Zcalc

8Ik1711

3^46465

2616

161532321935

7

107

13-142726-17

43-4o-48

7- 11326-17- 3- 4-12

3-04-21-34*27440

- 92

-14- 8

20

IBable 3°~'"0'foserFed and calculated structure factors for aiEKitroseite and paramontroselte

Kkl

2,11,02,12,02,13,02,14,02,15,02 5 l6,02,17*02,18,02A9,02,20,0

3103203303403503603703803903,10,03A-1.03,12,03A3,03AM3A5,03,16,03A7,03,18,03A9,0

4004io42043044o45046o47048o4904,10,04,11 ? Q4,12,04,13,0

Montrtiseite

8*7

6.317«413*610,8

11 fl 6

11,042.237°65«l

20*620 0226 .5

7»4

8.722«3

ll«414,6

17.039 .^

17aO

8.123,4

7«59 .1

22«2

10,8

22a3

F— eale

-n.85*0

- 6 0218,814*7

-10 «32,6

- 9*6- 6.1

10.137*0

-°37<»o- 5«3

4,0-24.421 «028,7

08.0

- 6,8-25 « 2

8.7

8^29»5

-13,3- 8.3- 2.9

17.04o*7

- 3.717*0

- 8 0 0'-27 »4

7.112.3

1 0421,6

- 6,6«rl O OJu£» d£«

- 2,6-19.0

ParaMJntroseite

-©bs — calcv

•1*

848

7

11

10

221617

1516

7

1-S

- 9-35

317

w J

22- 4-15- 1

-24-1416

-101018

- 3- 2- 6- 6

Table 3*—Observed and calculated structure factors for Htontroseite and parafflontroseite-r-Continued*

hkl

4A5^04,16,04,17,04,18,04,19,0

5105205305405505605705805905,10,05,11,05,12,05,13,05,14,05,15,05il6,o

6006106206306406506606706806906,10,06,11,06,12,06,13,06,14,06,15,0

710720730740

Mmtroseite Sobs

14,8

30,710 0 813.87*4

21.0

22.7

10.4

18 o9

17.4

14.4

6.5

28 .4

22.0

10.2

12 08

10,617*18.1

12*6

Scale

10.0- 0.8

3*3- 3*7-17.1

3-732.110 »3-15-0- 6 02-20 a0

21,9- 5.1

7.0- 6.1-20.2 .

1.62,6

- 3,713*4

- 6,013»43*38«78.5

-27*0- 5*8•- 4.6- 6,621.75*4

-11*9- 1.5- 5*4- 5*316.4

-10,516 0Q6,7

-13-0

BaraniDntroseite Sobs Scale

V

-107 - 4

19 191

151

6 -10

15 -1423

22

Table 3»—Observed aad calculated structure factors for BKmtroseite and paramoatroseite—Contimxed.

hkl

7507607707807907,10,07,11,07,12,0

8008108208308408508608708808908,10,0

9109209509^0950960970

10,0,010,1,010,2,010,3,010,4,010,5,010,6,010,7,010,8,0

11,1,011,2,011,3,0

Montroseite Sobs

12,012.810.8

11 aO

20*89*5

12.6

11,0

11.8

10,0

15*5

5.7

9*5

11.6-8,5

10.0

9,1

Paraiaontrose ite Hcalc Zobs Zealc

6,1-12,8-12,69,87»l3-712«4

- 8,3

-21,711.12.93.810.7

- 7*3- 9,34*1

- 1.45.111.9

- 8,53.5

l4 035.00-5

- 2.111.8

-5-7- 0.92.90.5

11.91.3

- 7.60

-10.4

.47- 3.69.5

23

Table 5«—Standard errors of atomic positions in montroseite and paramontroseite.

Montroseite Pararaontroseite

0.0037 A

0.015 A

0»3 percent

0.015 A

OoOTO A

0»5 percent

Figure 1.—Buerger precession photograph of the (Ok/) net

plane of a montroseite crystal showing sharp and

diffuse spots.

61414 61

25

(a.)

Figure 2.—Electron density projections along the £ axis of

(a) montroseite and (b) paramontroseite. Dotted contour

2 represents 2 electrons per A j other contours at intervals

of 2e/A2 .

26

o o

o d o o o

Figure 3»—Interatomic distance vectors in montroseite and

paramontroseite, (See table 4.)

Table k. —Interatomic distances in montroseite and paramontroseite

Atoms

V-V

Vector Montroseite (A) Paramontroseite (A)

V-O A1 B(2)

V-°H C(2)D

0-0 E(2)FG(2)H

0T -0T J(^)c-axis (2)

°II"°II K( 2 )L(2)

1.91*-1.962.102.10

2.912.682.962.632.933.032.593.31

+ 0.017+ 0.017+ 0.017+ 0.017

+ 0.02+ 0.02+ 0.02+ 0.02+ 0.02+ 0.01+ 0.02+ 0.02

1.881.912.002.13

2.882.652.793.872.862.932.653.0^

+ 0.07+ 0.07+ 0.07+ 0.07

+ 0.10+ 0.10+ 0.10+ 0.10+ 0.10+ 0.02+ 0.10+ 0.10

3.306 + 0.011 3.16 + 0.03

27

o

Figure 4.—View of crystal structures along the £ axis of

(a) raontroseite and (b) paramontroseite.