ROSSITE AND METAROSSITE;: TWO'NEW VANADATESFROM COLORADO.
By WILLIAMF•. FOSHAG
Assistant Curator, United States

Nationa~

MuseumAND
FRANK L. HEss

United States Bureau of Mines

OCCURRENCE
Oontributed by Frank. L. Hess

The mineral described in this paper was found in veinlets cutting
McElmo sandstone in Bull Pen Canyon, San Miguel County, Colo.,{) miles southeast of Summit Point post office, Utah near the point
where the 38th parallel cuts the. boundary line between Colorado
and Utah, and is on the western edge of the known carnotite-bearing
sandstones of the area. The deposit from which it came is on aclaim belonging to M. E.O'Neil, and to Mr. O'Neil I am indebted
for his courtesy in allowing me to examine the deposit, to collectspecimens, and for other specimens which he sent me later. At theleft of the eritranceto one of his prospect tunnels known as theArrowhead was a considerable amount of soft, dull brownish-red
sandstone which owed its color to a. mixture which seems to bemade up of hewettite, vanoxite, androsco,elite, though when mixed,
as in this deposit, these minerals are very difficult to identify.
Wherever I have seen sandstone with.similar aggregates of minerals,
it has been soft and friable, so that cracks in which minerals may
form are easily developed. In certain parts .of the sandstone are
the usual carbonized plant remains· that characterize the carnotite
deposits in sandstones of McElmo age in the plateau region. Here,and·there were rich spots .and streaks of carnotite. Veinlets of apale yellow, flaky .mineral ranging Jromthe thickness of cardboard
to one-half inch, and several feet long cut the. sandstone at various
angles. Gypsum is so common in the sandstones that 1 at first supposed that it formed the veinlets,:but closer examination showedthat the mineral had. only one prominent, cleavage and so could not
No. 2707.-PROCEEDINGS

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U. S. NATIONAL MUSEUM, VOL. 72,"ART. H.
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be gypsum. Excellent material was available and was collected, but
all was milky. Later I received from Mr. O'Neil further specimens
which had glassy centers and milky rims which were apparently theeffect of dehydrat~on. The mineral was later than the carnotite andother uranium and vanadium minerals in the deposit.
Although fairly plentiful at the point of discovery, this is the only
deposit in which I have found the mineral after an examination of
hundreds of carnotite deposits. It is entirely possible, however, thatsome veinlets in other deposits thought at the time to be gypsum maybe this mineral.
We have named the clear, glassy mineral rossite in honor of Dr.
Clarence S. Ross, of the United States Geological Survey. Since it
was found that the lighter yellow, flaky mineral differed from thedear material in degree of hydration as well as in its optical properties, it was deemed advisable to distinguish them in mineralogicalnomenclature. We therefore propose to call the naturally dehydrated form metarossite, a name that refers to its relation to rossite
as well as to its probable mode of genesis.
ROSSITEINTRODUCTION

Rossite was found sparingly in the second lot of material obtained,
only as small lumps in the. flaky mineral. When either rossite or
metarossite is dissolved in hot water and allowed to crystallize thecrystals have a composition corresponding to the natural rossite. A
chemical analysis was made on the natural mineral as well as one
on the recrystallized product. Inasmuch as no natural crystals ofrossite were found the crystallography is based entirely upon therecrystallized compound. The optical properties were also determined upon the recrystallized mineral.

(

CHEMICAL PROPERTIES

I

f
I:

Oontributed bv William F. Foshag
PYllOGNOSTICS

Rossite when heated before the blowpipe fuses easily to a black
bead without imparting any color to the flame. Heated in a closed
tube it fuses easily and gives off water. The mineral is slowly but
completely soluble in water from which it can be recrystallized.
Moistened with concentrated hydrochloric acid the mineral turns
mahogany red (vanadic acid). When an acid solution of the mineralis reduced with hydrogen sulphide or sulphur dioxide it becomesblue in color.

'frrART. 11

3

ROSSiTE AND METAROSSITE-FOSHAG AND HESSAl'ULYSES

Sufficient material in the form of hard, glassy cores of rossite
could be selected from the more flaky mineral and cleaned by rubbing
the soft metarossite off. The rossite could not be completely purified by this means, but the sample analyzed carried only a small
percentage of the metarossite and a few per cents of sand grainsfrom the inclosing sandstone. For a second analysis a quantity ofthe metarossite was recrystallized and the clear, glassy crystals so
obtained used.
Water was determined as loss on heating. Since the mineral
fused easily, a low temperature was sufficient to accomplish the complete expulsion of the water. Actually most of the water was driven
off at a temperature of 120 0 C. As the dehydrated mineral is very
slowly soluble in water, another portion was taken for the otherconstituents. The mineral was dissolved in hot water, the insoluble
matter filtered off, and the vanadium precipitated as mercuric vanadate and ignited to the oxide. Lime and magnesia were determinedin the usual manner. Constituents precipitated by hydrogen sulphide in acid solution (Pb, Cu, Mo, etc.) were found to be absent.
Iron and phosphorus could not be detected.. The results follow:
TABLE

l.-Analysis of rossite

Constituent

Natura!
glassyRecrysta!·
lized

22.90
18.00
0.14

22. 5918.48

f

Water (H,O) ______
Lime (CaO) _____ ~_Magnesia (MgO) __Vanadic 0 x ide---------

I:

Insoluble _________(V,Os) __ -- - -- ---58. 001.60---------

100. 64

99. 99(l58. 92

Ratios

Theoretical
CaO,V,O,.4H,O

1,255
330

4XO.963lX1.012

23. 22
18. 07323

1XO.990

58. 71

Rossite is therefore a simple hydrous .calcium vanadate. Its composition is expressed by the formula CaD. V 2 0 5 • 4H2 0. In the lastcolumn of Table 1 the theoretical composition for this compound isgiven.
CRYSTALLOGRAPHY

Oontributed, by William F. Foshag
GENERAL,'"

None of the specimens of rossite show any crystallographic forms.
The mineral, however, is soluble in water, and material suitable forgoniometric measurements can easily be obtained by recrystallization.
The habits of crystals obtained in this manner were all very similar,
and repeated recrystallizations under various conditions failed toI

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PROCEEDINGS OF THE NATIONAL MUSEUM

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I

vary the habit greatly. The crystals best suited for measurement
were about a millimeter or less in length; the :£aces of the larger
crystals were too curved while the largest were an aggregate of a number of individuals apparently complexly twinned. Except for one
lot. thit was tabular in habit all crystals obtained were prismatic.
More than 50 crystals were mounted on the goniometer and provisionally examined,.but only 15 were found to be entirely suitable andcompletely measured. The measurements showed rossite to be triclinic with the forms c (001), b (010), a (100), m (110), and y (101).
Because of the absence of pyramids on all of the crystals the axial
ratiqs and the numerical value of q were not calculated. The polar
elements were determined to be as follows: wo=.4969, Yo=.1624,
Po=.8295, "\=80° 39', p.=59° 31', v=~85° 38'. The axial angles are
0.:=98°18', {3=97° 24', y=89° 34'.

I

I

CALCliLATION

Cr)'stal No.

/

I'

i

I'
I

OF THE. ELE~IENTSThe crystals were measured on the two-circle goniometer, the prismatic habit rendering it easy to adjust them in polar position. The
prominence of the brachypinacoid and the good brachypinacoidal
cleavage gave satisfactory results for v. a The forms whose measurements could be used in the calculation of the elements were the following: a (100), 1n (110), b (010), and c (001). No pyramids could befound on any of the crystals, and repeated recrystallizations undervarious conditions failed to produce any habit with the slightest
pyramidal development. The axial ratios and the numerical value
for q were therefore not determined. All measurements were madeupon the artificially recrystallized mineral. The suitable measurements of the four forms upon which the elements are based are
given below:
TABLE

i,

f

r

r

,l

2.-Measurement of a (100) r08site
Reflection

Size of faceo

2_ __ __ ___ __ __ ___ ExcellenL __
3
do
c
3
1
4
do

_ MediumdodoNarrow

Good_~

_

,.

86 22
86 49

J
I,

_
_ 87 8_ 86 10I_ 86 58_ 85 40_ 86 15_ 85 46_ 85 49_ 85 10_ . 83 3

(

87

I

4

E-x-c"e11~~t= == ==== - ii~d~o~~======_ 84 33
do
86 53

6g= == == === == === =T Good

do

6

8
do
8
do
10
,
do
10
-do
12
do
13__ _____ _____ __ Excellent

A verage_ -

~

·
~

:..

do
Broad
MediuIIl
do
do
do
do

r

I
'
-1------------------------------ ·85 38
(

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5

ROSSITE AND METAROSSITE-FOSHAG AND HESS

ART. 11I

TABLE

3.-Measurement of m (110) rossite

I

I

Reflection

Crystal No.

I

2
3
3

/'

ExcellenL
do
do
Good
do
do
do
ExcellenL
Good_ _ _ExcellenL_____ do

4
4
6

8
10
10__

I'

12

Size of face

Broad
do
do
do
Mediuffi
do
Broad
do
__ _ Mediuffi
Broad
do

~

Average'

TABLE

Crystal No.

•

_
_
_
_
_
_
_
_
_
_
_

54
53
53
53
53
53
52
54
52
52
52

5
45
43
57
2
27

_

53

48

47
55
31
28
3

4.-Measurement of c (001), r08site
Reflection

Size offace

"
o

2
3
4
7

Excellentdododo11•....•..........dO.... __Large______
do
do_______
do_______

73

39

73
72

11
29

do... ....

::--I'..

Average__ I_ --__ ------- ---__ ------_[TABLE

Crystal No.

31
31
31
31

18

31

34
24
27
26

54

31

31

_

43

5.-Measurement of y (101) rossite
Reflection,,,

Size of face

/

o

Good
Medium_________ dododo
-I do .. _.. ~L~------------ Twin, excellent__
do_______
Ldo
do_______

~~_

15

1i

I

Average__ ----------------i----~-------

44
44
43
44
44

0

20
30
47
6
24

-87
86
86

22
27
5

1---1---1

44

13-86 '38

In this compilation the angles are listed as "excellent" when thereadings between two faces were designated" excellent" during measurement; and listed as " good" when the readings for the faces were
between " excellent" and " good" or between" good" and " good." Itwill be noted that even in the cases where the faces are all designated as"excellent" the measurements'range from 83 0 38' to 84 0 49', a difference of over 3 0 for ep for (100); and from 52° 2' to 54° 47', a differenceof almost 3 0 for ep for (001). This variation is large for crystals so6PROCEEDINGS OF THE NATIONAL 1\IUSEUM

VOL. 72

well suited for crystallographic measurement and the cause is notentirely clear. The average values for ep and p of the forms of rossite
are given in the following table:
TABLE 6.-Averages of measured angles of rossite

Number ofmeasurements

Form

a

(100) __________m (110) __________c (001)-----------Y (101) ________ --

tf>

0

14
11

5
5

,

p

,

,

0

85 38
53 48
72 54
-86 38

I

90 0
90 0
31 31
44 13

I'
I

The value of the elements based on these measurements are as
follows:
7.-Axial elements of rossite

TABLE

Projection elements

Polar elements

xo'=0.5829
Yo'= .1906
Po'= .9730
qo'= 0,

Xo=0.4969
Yo= .1624
po= .8295
qo=

38

v=85

r=l0

f

Linear elements

I

0

I

A=80 39
JL=59 31
11=85 38h=18
24
1'=89 34
a=98
{J=97

FORMS AND ANGLES

Except for the forms b (010), a (100), m (110), (J (001), andy (I01) no others were found except a few doubtful ones. These
doubtful forms were observed only once each and may represent,in part at least, nothing more than the smooth surfaces by which the
crystals were attached to the walls of the crystallizing dish. All theforms noted with the average angle of each are given in the tablebelow:
TABLE

NumberLetter

S.-Measured forms of rossite

NumberNumber ofmeas- Symbolof crysure·
tals
ments

'"

15
15
001
15
30
.010
15
30
100
15
30
110
5
101
5
1 ------ ------1 ------ ------1 ------ -------

72
0
85
53
":"86
96
61
35

- - ---

1______ c________
2______ b________
3______ a_______
4______ m'- ______
5______
6______ y---.----7______ ---------8______ ------------------~

(

0

p

,

0

,

54
00
38
48
38
21
10
24

31
90
90
90
44
64
44
88

31
00
00
00
13
00
00
23

ART.l!

ROSSITE AND M:ETAROSSITE--FOSHAG AND HESS

7() (001). The basal pinacoid was found on all of the crystals measured andis usually the only terminal face present. Very often it is smoothly curved.
b (010). The brachypinacoid is always the most prominent face in the prismzone and is always bright and smooth.
a (100). The macropinacoid is always present, but is variable in size. ranging
from broad to narrow. Its relative size is dependent upon the size of the unit
prism.
m (110). The unit prism is usually present as a medium to broad face, but
may be absent. Next to the clinopinacoid it is the most prominent face on the
crystals.

b

a

b

a

A

B

FIG. 1.-A AND B. CRYSTAL HABIT OF ROSSITE

There are no other faces present in the prism zone. Those present are always
sharp, without striations, but some are slightly curved.
V (101). The face of the macrodome is present on some crystals but is
usually smoothly curved so that accurate measurement was impossible. It is
often present as a small triangular terminal face, but sometimes becomes asprominent as the base.
HABITS

The crystals of rossite are commonly of a prismatic habit (fig. 1),
but a habit tabular to the base was found in one lot of crystals. The

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prismatic habit varies somewhat, due to the relative size of the macropinacoid and the unit prism. "When the orthopinacoid is large thecrystals have an almost equal horizontal thickness. 'Vhen the prismis prominent and the macropinacoid small or lacking the crystals arealmost lathlike. The length of the crystalsaalso varies. Many crystals showing a combination of the three pinacoids are stumpy and evenalmost equidimensional; in the latter case they
appear as rhombs. The crystals rarely are longneedlelike blades.
TWI~~I~GbaAmong the larger crystals twins are the rule
but are so intricately intergrown that it is difficult to know just what relations the individuals
have to each other. Among the smaller crystals
twins are rare. In one lot, however, twins having the general appearance of the butterfly twinsof gypsum were found. In these the twinningplane is the macropinacoid (100). These twins
are similar to Figure 2.
PHYSICAL AND OPTICAL PROPERTIES
Oontributed by William F. Foshag

The color of rossite varies from Martins yellow in the small crystals to pinard yellow in thelarger-crystals. The lustBr varies from vitreous
pearly to glassy. The hardness lies between 2ba m
Illld 3. The specific gravity, determined by floating clear crystals in a suitable bromoform-carbon
tetrachloride mixture is 2.45. The fresh mineralis brittle and has a good cleavage parallel to theclinopinacoid.
Rossite is a biaxial with a large axial angle.
The plane of the optic axes is essentially parallel
FIG. 2.-TwIN CRYSTAL
to the axis (] with Z=c and roughly bisects the
OF ROSSITE
angle between a (100) and b (010). The baseand the brachypinacoid show the emergence of an optic axis near theedge of the field. The extinction direction measured on the basal
plane and from the edge 001-010 was found to be 16° :t:3. The
indices of refraction measured on the recrystalized mineral by theimmersion method are as follows:('.(=1.710, ~=1.770, y=1.840

1I'IART. 11nOSSITE AND METAROSSITE-FOSHAG AND HESS

9

The dispersion is very strong; the emergence of an optic axis appears
as a broad band of colors. The high dispersion manifests itself inbright-colored flashes when the crystal is mounted and revolved on
the goniometer.
:METAROSSITE
GENERAL

The mineral that occurred most abundantly in the material received is what we here call metarossite. It forms small yellow veinsin a light gray and friable sandstone, is coarse, platy in habit, but is
soft and friable. Occasionally within the center of masses of metarossite one can find small glassy kernels of rossite. The relation of
the metarossite to the rossite suggests that it is a dehydration product of that mineral. As will be evident from the analyses given
further on, the mineral is a distant hydrate and not a partiallyaltered rossite. Two analyses made on different lots agree very wellwith each other and with the theoretical values for the formula
assigned to it: CaO.V2 0 5 .2H 2 0. vVe feel justified, therefore, inassigning a distinct name to this compound.
CHEMICAL PROPERTIES
Contributed by William F. Foshag
PYBOGNOSTICS

The behavior of metarossite before the blowpipe is entirely similar
to the rossite. It is,' however, somewhat more slowly soluble inwater. Its chemical reactions are identical with those of rossite.
ANALYSIS

Abundant material was available for analysis. (No. 95331, U. S.
N. :M.) Two different samples were submitted to chemical analysis,
one from the first lot received and another from the second lot.
The samples were carefully chosen, only the larger and purer cleaNage fragments being selected. Upon examination under the petrographic microscope the large majority of the flakes were clear andtransparent, but the very large grains had a somewhat muddied appearance, due to included air. There were occasional grains of sandfrom the inclosing sandstone, estimated to amount to about 2 per
cent. The analysis was carried out according to the scheme outlined
under rossite, with th~ following results:

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TABLEVOL. 72

9.-Analysis of metarossite

NaturalPearlyRatios

Theoretical
CaO.V,os.
2H,O

Water (H2 O) _______
Lime (CaO) ________
Magnesia (MgO) ___Vanadic oxide (V2O.)_
Insoluble __________

13.56
20.04
0.10
64.08
2. 72

14.08
19.60
0.13
64.20
2.48

100. 50

100.49786
362

2X 1. 088
IX 1. 003

13. 14
20.44

360

1XO.997

66.42

Metarossite is a hydrous calcium vanadate of the formula
CaO.V20 5 .2H2 0. It differs from rossite in its lesser hydration, thatmineral being the similar compound with four molecules of water.
If rossite is left exposed to the air it gradually becomes lighter incolor, loses its vitreous luster, and passes over into metarossite, still,
however, retaining its platy structure. If metarossite is dissolvedin water and allowed to crystallize, rossite separates out, but theglassy crystals so obtained gradually pass over into the metarossite
again. It was at first thought that this change of the higher hydrate
to the lower one was continuous, similar to the changes in hydrationin other platy minerals, notably carnotite, autunite, etc. There areseveral facts, however, that point to the existence of two distinct
hydrates. First, there is the occurrence of rossite as sharp residual
kernels in the metarossite without any suggestion of gradation; and,secondly, the two analyses made upon separate lots of material agree
satisfactorily with each other and very well with the theoreticalvalues for the dehydrate.
CRYSTALLOGRAPHY
Oont1'ibuted by Willian~ F. Foshag

No measurable crystals of metarossite were found, although on one
specimen a crust of the vanadate showed projections resembling
crystals. They were too imperfect, however, to be measured or toeven suggest the symmetry of the crystals.
PHYSICAL AND OPTICAL PROPERTIES
Oontributed by William F. Foshag

Metarossite is light yellow in color (Martius yellow, Ridgway)and has a dull pearly luster. It is soft and friable and cp,n be easily
crushed between the fingers. Due to its decided platy cleavage

.!RT.ll

ROSSITE AND METAROSSITE-FOSHAG AND HESS

11

(probably inherited from the rossite) it breaks easily into flat, flaky
grains. These under the microscope are clear and homogeneous.
This platy cleavage makes it difficult to obtain good quantitative
measurements of its optical properties. Like the rossite the cleavage
flakes show the emergence of an optic axis with a very high dispersion. The indices of refraction are considerably higher than those ofrossite. Only a was within the range of the oils available and wasfound to be 1.840, {3 and y were both somewhat higher than 1.85 but
could not be measured directly because the ease with which themineral dehydrated and melted prevented the use of piperine-iodide
melts. The birefringence is high and so far as could be determined
the minerals showed no pleochroism.

RELATION OF ROSSITE AND METAROSSITE TO OTHER
MINERALS
There are no known vanadates having the composition of these
two minerals nor any arsenates or phosphates similar to them. They
are, however, members of a series with the other known calcium
vandates found in nature, hewettite, and pascoite. Tripling theformulre of rossite and metarossite brings out the following interesting relation:
Hewettite
Pascoite
RossiteMetarossite

1 GaO. 3 V.O,. 9 H20.
2 GaO. 3 V,O•. 11 H 20.
3 GaO. 3 V,O,. 12 H,O.
3 GaO. 3 V20•. 6 H 20.

-'-

The relation of metarossite to rossite is not entirely clear. It is
possible that in common with many other minerals with a decided
platy cleavage the water content is variable and that the compound
can lose water without any great change in its molecular structure.
The ratios for the two hydrates show, upon analysis, such good
agreement with the theoretically required amounts without any evidence for any intermediate steps that it seems possible that we are
dealing here with two distinct hydrates and not with a continuous
series. Even were this not the case it is deemed advisable to separate
the two compounds in mineral nomenclature in order to avoid
confusion, the properties of the two substances being so greatly
different.
SYNTHESIS

Both pascoite and rossite have been synthesized by 'Valdemar T.
Schaller 1 by heating hewettite suspended in water with precipitatedcalcium carbonate on the steam bath and allowing the clear solution
1

Unpubllshed data.

12

PROCEEDINGS OF THE NATIONAL MUSEUM,oL.12

to crystallize at room temperature. Rossite was formed when the
calcium carbonate was present in excess. The crystals iormed in thisway are similar in every respect with those obtained by recrystallizing
the natural rossite or metarossite. If the synthetic mineral is left
exposed to the air it eventually loses water and passes over into
metarossite.
SUMMARYBOSSITJD

Name.-In honor of Dr. C. S. Ross, of the United States Geological Survey.
Ohemical properties.-A hydrous calcium vanadate, CaO. V20~.
4H2 0. Analysis: CaO 18, MgO 0.14, V 20 S 58, H 2 0 22.90. Sum
100.64. Soluble in water.
Orystallographical properties.-Triclinic. wo=0.4969, Yo=0.1624,
po=0.8295, '\=80° 39', ",,=59° 31', v=85° 38', u=98° 18', f3=97° 24',y=89° 34'. Habit prismatic. Forms: c (001), b (010),·a (100),m (110), Y (101).
Physical and optical properties.-Color yellow. Luster pearly tovitreous. Biaxial. 2V large. Plane of the optic axes parallel tothe axis c with Z=c.
u=1.710, {3=1.770, y=1.840. Dispersion strong. Hardness: 2-3;
specific gravity 2.45.
Occurrence.-Found as small glassy kernels embedded in flaky
metarossite at Bull Pen Canyon, San Miguel County, Colo.
)IET.HIOSSITE

Name.-In allusion to its relation to rossite, a partially dehydrated
rossite.
oh.emtical properties.-A hydrous calcium vanadate, CaO. V20~.
2H2 0. Analyses OaO 20.04; 19.60, MgO 0.10; 0.13, V 2 0 S 64.08;
64.20, H 2 0 13.56; 14.08, Insoluble 2.72; 2.48. Sums 100.50; 100.49.
Soluble in water.
.
Physical mndJ optical properties.-Color yellow. Luster pearly todull. Biaxial. 2V large. Dispersion strong.
a= 1.840, {3 and y higher than 1.85. Soft and friable.
Occurrence.-Found as small veinlets in sandstone at Bull Pen
Canyon, San Miguel Canyon, Colo., as a dehydration product ofl'ossite.

o