THE AMERICANMINERALOGIST,

VOL

46, NIARCH APRIL,

1961

N O R S E T H I T E , B a M g ( C O g ) 2 ,A N E W M I N E R A L F R O M T H E
GREEN Rr\rER FORI,IATrON, WYOMTNG*
M,q.nvE. Mnosn, E. C. T. Cneo, Josuru J. Fanov, AND CHARLES
MtttoN, U. S. GeologicalSurvey, Washington 25, D. C.
Assrn,{crNorsethite, BaMg(CO):, was found in dolomitic black oil shale below the main tiona
bed in the Westvaco trona mine in Wyoming, associated with shortite, labuntsovite, searlesite, loughlinite, pyrite, and quartz. It also occurs there in gray shale with abundant
shortite and northupite, some searlesite and loughlinite, in a fine-grained matrix consisting
essentially of quartz and pyrite.
Norsethite occurs as clear to milky-white circular plates or flattened rhombohedral
crystals, 0.2-2.0 mm. across. The mineral is insoluble in water but is readily decomposed bycold dilute hydrochloric acid. Norsethite has hardness about 3.5; density 3.837+0.005(meas.),3.840 (calc.); luster vitreous to pearly; fracture hackly; good rhombohedral cleavage. It is infusible before the blowpipe. Norsethite is uniaxial negative, and the indices ofrefraction are a:1.694 and e:1.519. X-ray crystallographic studies show that the crystals
are rhombohedral and have the following characteristics: possible space groups, RBzz,
R3m, or R32, the most probable being R32 (D37), a subgroup of R3c, the space group of calcitel hexagonal a-5.020+0.005 A, c:16.75t0.02;
rhombohedral a6,:6.29'10.01 A,
a:47"02'*05t1 volume 365.6 A3 (hex.);cell contents: 3[BaMg(CO)z], in the hexagonalu n i t . C r y s t a l f o r m s o b s e r v e d a r ec { 1 0 0 0 1 } ,a l l l 2 0 l , m { 1 0 T 0 } , a n d r { 1 0 1 1 } . T h e s t r o n g e s t
r-ray lines are:3.015 A (too),3.860 (35), 2.656 (35), 2.512 (35),2.104 (35), 1.931 (35),
1 . 8 6 4( 3 5 ) .
Norsethite has a structure similar to that of calcite. The structural relations of norsethite. dolomite. and calcite are discussed.
Chemical analysis of a 0.1 gm. sample gave: BaO 52.9,CaO 0.5, MgO 13.9, FeO0.4,
MnO 0.1, COz3l.2, Na2O 0.2, SiOr 0.3, insoluble 0.4, total 99.9 per cent.
Norsethite is named in honor of Mr. Keith Norseth, engineering geologist of the trona
mine at Westvaco, Sweetwater County, Wyoming.

INrnonucrroN
The new mineral norsethite, BaMg(COa)2,was discoveredduring theinvestigation of the authigenic minerals of the Green River formationof Wyoming, Utah, and Colorado. ft occurs in microscopic quantities
at the Westvaco trona mine which is about 18 miles west of Green
River, Wyoming. So far, norsethite has not been found at any otherGreen River locality.
The specimensthat containedthe crystals of norsethitewere collectedby Charles Milton who first observed this new mineral and named it inhonor of Mr. Keith Norseth, engineeringgeologist at the Westvaco
trona mine, in grateful acknowledgment of his friendly assistancein themineralogical studies of these authigenic minerals.
Publication authorized by the Director, U. S. Geological Survey.

420

BaMs(CO)z
NORSETHITE,

42r

OccunnpNcB ol NoRSETHTTE
Norsethite first was observed as clear to milky-white plates flattenedparallel to the basal pinacoid (Figs. 1 and 4) in the dolomitic black oil
shale which underlies the main trona bed at the Westvaco trona mine in
Wyoming. There the mineral has been found associated with shortite [NazCaz(COt r], labuntsovite [(Na,K) z(Ba,Mg) (Ti,Al, l'e,Nb) zSiaOrr(OH)ul, searlesite [NaBSizOo'HrO], loughlinite [NazMgeSioOre'8HzOl,
pvrite, and quartz. Norsethite also occurs at the Westvaco mine in agray shale that consists largely oI quartz and a small amount of pyrite; the associated minerals are abundant shortite and northupite
and lesseramounts of searlesiteand loughlinite. The[NaaMgCI(CO3)2],
residueof trona core from an unknown depth, drilledwater-insoluble
in the area of the Westvaco trona mine, yielded discoid masses ofnorsethite(Fig. 2).In addition, good crystaisof the type shownin Figs.
1 and 3 were obtained from the waste ssdiurn carbonate "mud" dischargedfrom the soda-ashprocessingplant at Westvaco,along with pyrite, shortite, dolomite, calcite,labuntsovite,barytocalciteICaBa(COr)z],
and witherite [BaCOs].
leucosphenite[Na3CaBaBTisSisOzs],
found in the dolomitic oil shalesof
has
not
been
Thus far, norsethite
Utah or Colorado.
MrNnnar, SrpenerroN
Norsethite crystals were isolated from the rock specimens,the tronacore, and the lvaste sodium-carbonate"mud" by heavy-liquid separation(bromolorm), followed by hand-picking under the binocular microscope.
Associatedwith norsethite in the waste "mud" were crystals of barytocalcite and witherite, nearly identical in habit with those of norsethite.
Norsethite could not be distinguished readily from barytocalcite andwitherite by means of indices of refraction, or by specifrcgravity, since
Clerici solution attacks carbonates.It was necessaryto check each individual crystal of such habits under the microscope; norsethite is uniaxial
negative, whereasbarytocalcite and witherite are both biaxial negativewith small 2V.
The material submitted for the chemical analysis (0.1 gm.) was obtained from a single specimen of dolomitic shale which was free frombarytocalcite and witherite. In this instance only bromoform separation
was required.
Puvsrcar,lNl

Oprrcrlr- PnopBnrrns

Norsethite occurs as clear to milky-white circular plates or flattenedrhombohedral crystals with diameters ranging from 0.2 to 2.0 mm.
(Figs. 1-4). Some crystals, as well as irregular grains, show corrugatedM. E. MROSE, ET AL,

o
d

d

!

d

E
.o
4i

bo

>5
Oa'

6u
E:il
tr

'N
A ia t

)

MO'

>>'l

a2l
Q bar
:or

' 9

l

ZE)
*6id

:

NORSETHITE,BaMg(COs)z423

or flattened edges; the thick corrugated grains are pumpkin-shaped.
The mineral has a vitreous luster, a hackly fracture, and good rhombohedral cleavage{1011}. Its hardnessis about 3.5. Norsethite is insoluble
in water but is readily decomposedby cold dilute hydrochloric acid. It
is infusible before the blowpipe. The specific gravity, determined on
small crystals of norsethite on the Berman microbalance, using toluene
as the immersion liquid, is 3.837+0.005 (an averageof six different determinations); for large crystals, 3.81010.005; the calculated specificgravity is 3.840. Most of the crystals of norsethite that were examined

Fro. 5. X-ray powder photographs (Cu Ka radiation). (above) Calcite, Westvaco tronamine, Sweetwater County, Wyoming. (middle) Norsethite, Westvaco trona mine. (beiow)
Dolomite. Binnental. Switzerland.

under the microscopeshowed fluid inclusions or cavities; some appear aschannelsnormal to, and in between,the rhombohedralfaces,as shown in
Fig. 1 and 4. The presenceof cavities and channels in the large crystals
undoubtedly accountsfor the difference between the observed and calculated values.
Optically, norsethite is uniaxial negative. The mineral is colorlessintransmitted light. The indices of refraction were determinedby the immersion method using sodium light and were corrected to 25o C. The
error of measurementprobably is not greater than *0.001; a:I.694
a n d € : 1 . 5 1 9 ;A : 0 . 1 7 5 ( N a ) .
The rule of Gladstone and Dale l(n-I)/d:Kl
was found to holdsurprisingly well for norsethite. Norsethite with d:3.837 (meas.) andK:0.16632 (based on the recalculated chemical analysis in Table 3)
givesdKf 1:1.638 for the calculated mean index and (2a-le)/3:I.636
for the measured mean index.

424

M. E. MROSE, ET AL.
CnvsrenoGRAPHY

Morphology
The faceson the well-formed crystals of norsethitegave only fair signals on the opticai goniometer. The forms observed were identified
readily from goniometricmeasurementscorrelatedwith the single-crystal
o-ray results. The morphology of the largest crystals measured (averaging 1.0 mm. in diameter) consistsonly of a well-developedbase [00011
and the rhombohedron{1011}. The small crystals (less than 0.5 mm. indiameter) showed, in addition, the first order prism {1010} and thesecondorder prism [tl20l, as very narrow faces.
The notable absenceof a bipyramidal form on any of the numerous
crystals examined made it impossible to determine the crystal classfrom
morphological considerationsalone. The crystals are holohedral in habit.
They gave no positive piezoelectricresponseon the Giebe-Scheibeapparatus. This evidence would suggestthat the crystal class is either rhombohedral (3) or scalenohedral(32/m). Both thesepossibilitieswere eliminated and the crystal class was establishedas trigonal-trupezohedral (32)from a consideration of the space group criteria and the structural relation of norsethite to calcite (seediscussionon page 426).
X-ray powd.erd.ata
An r-ray powder diffraction pattern of norsethite (film no. 11793)wastaken in a 114.59 mm. diameter Debye-Scherrercamera with nickelfiltered copper radiation (X:1.5418 A), using both the Straumanis andWilson techniques(Fig. 5). Film measurementswere correctedfor shrinkage. AII interplanar spacingsand intensities for the observedlines are
given in Table 1, column 2. The intensities were estimated visually bycomparisonwith a calibrated intensity strip. Interplanar spacingswere
calculatedfrom the s-ray cell constants down to a value of d6.,:1.995
A otr a digital computer using a program developed'andcarried out by
Daniel E. Appleman. All calculatedspacingslor d'ntr) 1.000A for norsethite are listed in Table 1, column 1.
Single-crystalx-ray d.ata
A thin, tabular, hexagonal-shapedcrystal of norsethite (approximately 0.5 mm. in diameter) was examined by the Buerger precession
method. A. quartz-calibrated precession camera was used with zirconium-filtered molybdenum radiation (I:0.7107 A) to obtain theh 0 . 1 , h I . l , , h k . O , h k . l , a n d h h ' I n e t p l a n e s .T h e s e p h o t o g r a p h se s t a b lished the lattice as rhombohedraland, together with the film measurements (correctedfor horizontal and vertical shrinkage),Ied to the crystallographic data given in Table 2.

NORSETHITE, BaMg(CO)z425

Tasr,r 1. Coupenrsowor X-Rev porlorn Dar,r ron Nonsrrnrrn.
Dorourrr, ANo Car,crre
Dolomite,CaMg(C(RossTownship,
Haley, Ontario(1)
Calculated.

(2)
Measuredb

hk.l

d n +tdn* t

0 0 .3
1 0 .1
ot.2
10.4
00.6
0 1. 5
11.0

5 583
4.208
3.859
3 016
2.792
2 654
2.510
2.289

5.584
4.210
3 .860
3.015
2.795
2.656
2.512
2 290
2 154
2.104

tt -J

02.1
20.2

r0.7

02.4
0 1. 8lto

0 0 .9
20.5
2t.l
12.2
02.7
10 10
2 1. 420.8
1 1. 9
12.5
03.0
01 11
0 3. 3 \z.lJo

2.104\
2.0e61| 929
1. 8 8 6
1. 8 6 7 1| .86rl
1.824
I

O.t.)

I 612\
1 .60eI
1. 5 6 3
1. 5 3 0
1. 5 0 8
1.495
r.475
1.449
l.+Jl

s0 3J

00.12
02.10
128
03.61

so.61
22.0
20.11
1 0 .1 3223
1 1. 1 2
1 3 .I

1. 3 9 6
1 355
1 327
1.293
1.286
1 255
1.247
1.235
1.224\
1.2201
r.203

1.864
1.824
r oJo
r.612
1 .563
1..530I .510
| 496
1.475
7.448
| 437
1.404
1. 3 9 8
I

JJO

1.328
1. 2 9 5
1.286
1 256
1 248
1.237
| 222

25
30
35
100
35
35
25
25
35
35
25

o

9
o

q.,- +1"^r:^Flowie andBroadhurst, 1958

Swanson and Fuyat,
1953

(3)
Measured"(4)
Measuredd

4 025
3.690
2.886
2.670
2.540
2.405
2.192
2.066
2. 0 1 5

J

100
10
8
10
30
15
I5

1. 5 6 7
1 496
1.465
| 445
| 431
1.413
1. 3 8 9

3.86
3.035
2.845

12
100
3

2.495
2.285

t4
18

2.095

18

r.927
1.913
1.875

20
30

.t.)

6
18
6
25
o

Calcite, CaCO3

r.ozo

2
5
4

10
4
-tJ

z

1. 5 8 7
1.525
1. 5 1 8
1. 5 1 0
|.473

r.M0

6
6
9
9
o

8

I

A

I .356
1. 3 3 9
| 297

All

9
o
4

|.247

.)
9
J

(Continued, on nert page)

5
ll
1i

1.235

2
q

n
J

2

M. E. MROSD, ET AL.

426

Tarr,r 1 (Continued.)rite,CaM
Ross Ton'nship,
Haley, Ontario
Horvie andBroadhurst, 1958

Norsethite, BaN{g(COg)z
Westvaco trona mine,
Sweetwater Co., Wyoming
Present Study(1)
Calculated'

hk.t

(2)

(3)

Measuredb

Measured"

1.193
31.2
21.10 1.173
1.159
13.4
1.154
0 1. 41.145)
22.6
1.1441
03.9
1.1M)
30.9
1. 1 3 531.5
0 0 . l s ] r1' r1r"/
12.11)
02.13 1.108
1.084
40.1
1.078\
04.2
1 . 0 7 I7
t3.7
1 .052
40.4
20.14 1.048
1.042\
31.8| .041I
2 2. 9
1.034
04.5
1 020
11.15
10.16 1.018\|.Or4J
2r.13
03.12\ r nn(
30.121(4)
Vleasuredd
dnn t

dt* t

dn* t

r.193
r.173
1.160
I . _tJ+

1.144

4
A

1.144
1 123

1 1795
1 15389
3
A

Calcite, CaCO3
Synthetic
Swanson and Fuyat,
1953

1 .096o,t

1.108
1. 0 8 6
1.077
1 051
1 .046

1 068

3
3
o

r.0473
1. 0 6 1 3
1.0447

o

J

1

J

3
A

3
1.006
0.9893o 97990 9717
0 96830.95590 94990 94690 93430.92230 91170.9017
0 89890.8961

6
3
3
6
6
3
3
3
4
3
3
4
6
3

0.973s

J

0.962
0.949
0 930
o.926
0.923
0 913
0.909
0 903
0 894
0.835
0 821

5
I
1
3
3
1
2
1
2

1.0352
r.0234
1 . 0 11 8
0 989s
0.9846o 9782v.9lol

0.s655

<1
2
<1
1
I
3
2

n

2

* This line was obscured by a Iine of the Si standard'

Structural relation to calci'teand.dolomite
A search oI crystal Data (Donnay and Nowacki, 1954) showed that
dolomite ICaMg(CO3)2]and calcite ICaCOa]have cf a ratios remarkably
close to that of norsethite [BaMg(cos)2]. This, coupled with the factthat these three minerals have remarkably similar crystallographic data
(Table 2) as well as physical and optical properties' strongly suggested

427

NORSETHITE,BaMg(COa)zthat norsethite must be a member of the same structure group as dolomite and calcite. Comparisonof the r-ray powder films (Fig. 5) and thepowder diffraction data (Table 1) for the three minerals indicated astrong structural resemblancebetween norsethite and calcite (spacegroup R3c), and betweennorsethiteand dolomite (spacegroup R3).
The Buergerprecessionphotographsof norsethiteindicated only threepossiblespacegroups for the mineral: R3rn, R3m, or R32. Neither R3aa
nor R3rn is a possiblesub-group of R3c or of R3. Since evidenceindicatesthat norsethite has a structure similar to that of calcite, and since R32
is the only one of the three possible spacegroups for norsethite which islisted as a sub-groupof R3c (the spacegroup of calcite), it follows thatthe spacegroup of norsethitemust be R32.
In order to elucidate the relation of the norsethite structure to thecalcite and dolomite structures, a determination of the structure of
norsethite has been undertaken and will be published in detail at a later
date.
T,qnr,n 2. CoulanrsoNor Cnysrer,rocn.a.pnrc Dar.q. lon Nonsrrnrro,
Dor,ourrr, luo Cer,crre

Mineral

Norsethite

Dolomite

CalciteLocality

Westvaco mine, Sweetwater Co., Wyoming

Ross Township, Haley, Ontario

Synthetic

Present Study

Howie and Broadhurst, 1958

Swanson and Fuvat,
1953

Hexagonal-R; trapezohedral-32

Hexagonal-R; rhombohedral-3

Hexagonal-R; scalenohedral-32/m

5 .020+ 0 .005A
1 6 . 7 5+ 0 . 0 2

4 . 8 1 0 + 0 . 0A
02
1 60 2 + 0 . 0 0 1
3. 3 3 0
6 . 0 2 0A
47"07',

Symmetry

Cell Constants
a
c
c/a

J.JJ/

&rlt

6 . 2 9+ 0 . 0 1A
47"02',+05',

q

4.9SA
9
r7.062
3.420
6 . 3 7As
46"M'Space Group
Volume (hex.)
Cell Contents (hex.)
Density (calc.)(obs.)*

365.6 A3
3[BaMe(CO3)r]
3 .8403.837+0.005

Quotedfrom Zen (1956).

3 2 1. 0 A 3
3[CaMg(CO)i]
2.872*
2.86*

3 6 7 . 8A 3
6[CaCOe]

2.7rr

428

M. E. MROSE,ET AL.
CuBlrrsrnv

Except for the determination of COz, the classical procedures of
Hillebrand et,al. (1953)were followed in the chemicalanalysisof norsethite which was made on a 0.1 gm. sample obtained from a single specimen. Carbon dioxide was determined volumetrically by measuring thegas evolved when the sample was treated with (1*3)HCI and, after
reducing to standard conditions, appiying the factor to convert volume ofCOz to mass (Fahey, 1946).
The quantitative spectrographic analysis for minor elements innorsethite, cited below, was made by Harry Bastron of the U. S. Geological Survey:
Ca
Na
Fe
Mn
Sr
Al

040
0.2
015
0.049
0.022
0.016

Sn
Ti
Cu
Cr
Be

0.002
0.001
0.00050.00040.0002

Looked for, not found: Ag, Au, Hg, Ru, Rh, Pd, Ir, Pt, Mo, W, Re, Ge, Pb, As, Sb,
Bi, Te, Zn, Cd, Tl, In, Co, Ni, V, Ga, Sc, Y, Yb, La, Zr, Th, Nb, Ta, U, Li, P, and B.

The chemical analysis of norsethite is given in Table 3. The formuladerived from this analysis is BaMg(COs)2. The recalculated chemical
analysisis in good agreementwith the theoretical composition.
T,r.sLE
3. Cnnurc,rrANer-vsrs
or Nonsrrnrre, BaMg(CO)z
Analyst:J. J. Fahey
Determined
Per Cent
BaO
CaO

Mso
FeO'
MnO
COz
Nuron
SiOr"
Insol d52.9
0.5
1 3. 9
0.4
0.1

3r.2

Recalculated

53.5
0.5
74.O
0.4
0.1
3 1. 5

0.2
0.3
0.4

u Total iron as FeO.
b Determined spectrographically by Harry Bastron.
" Soluble in (1*3)HCl.
d Insoluble in (1t3)HCl.

NORSETII ITE, BoM g(COs)z

429

Using the measuredspecificgravity determinationof 3.837,the chemical analysisin Table 3, and the cell constantsfor norsethite,the experimental molecular weight of the unit cell is 844.6. The calculated cell
contents approach very closely the formula 3[BaMg(CO3)r].
AcxNowr,BocMENTs
We are grateful to thesecolleaguesin the U. S. GeologicalSurvey for
their assistance:Howard T. Evans, Jr., who contributed helpful advice
and discussion;Daniel E. Appleman, rvho calculated the d-spacingson
a digital computer; Harry Bastron, who made the spectrographic
analysis; and Isidore Adler, who checked the crystals of norsethite forpiezoelectricity.
Rnrenrxcrs
DoNNev, J. D.H. .Luo Nowacrr, WnnNl;n (1954), Crystal Data GeoLSoc. Arnerica Memoir 6O.
Fauov, J. I. 0946), A volumetric method for the determination of carbon dioxide zz Wells,
R.C andothers,Contributionstogeochemistry,194245;Lr.S.Geol.Surtey&utrtr.95O,
t39-141.
Hrr,r,ennem, W F., Luuorr,l, G. E. F., Bnronr, H. A., eNo Hor.lue.N, J. I. (1953), Applied inorganic analysis, 2nd ed. John Wiley and Sons, Inc., New York.
Howm, R. A. nNt Bnoannunsr, F. M. (1958), X-ray data for dolomite and ankerite: ,4a2.
M,inerol., 43 1210-1213.
"
INrnnNarrowar,n T,llrr,r,rN zun BnsrruuuNc voN Knrsl.q.r,r,srnuxrunnN (1935), 1, p.
264. Gebriider Borntraeger, Berlin.
Swa.NsoN,H. E. e,r'nFuvar, Rurn K. (1953), Standard X-ray diffraction powder patterns:
U. S. Natl,. Bur. Stand.ard.s
Circ. 539,2,51-54.
Zru, E-AN (1956), Correlation of chemical composition and physical properties of dolomite: Am. Jour. Sci.254,51-60.
Manuscript receited lune 18, 1960.