THE CHEMICAL FORMULA
OF THE 'ZIRCON PYROXENES' AND
THE 'ZIRCON PECTOLITE'
BY
W. H. ZACHARIAS E N
he zirconiumbearing minerals: Låvenite, Wohlerite, Hiortdahlite
T and Rosenbuschite were found for the first time in the nephelite­
syenitic pegmatite veins of the Langesund fjord in Southern Norway.
W. C. BRøGGER has studied these four minerals very accurately1.
As a result of his examination BRøGGER concluded that these zir­
coniumminerals were closely related both crystallographically and
chemically to the Pyroxenes and to Pectolite. He therefore proposed
the name Zircon-pyroxenes for Låvenite, Wohlerite, Hiortdahlite and
Zircon-pectolite for Rosenbuschite. The following tables show the
relations:
Mineral
a:b:c
Diopside .............
Aegirite . .............
Låvenite
Wohlerite ............
Hiortdahlite
l,092: l : 0,587
1, 098: l :0,601
1,096: l: 0,7 15
1,054: l :0,709
1,058: l : 0,705
Pectolite . .. .. ........
Rosenbuschite . . . .... .
l,072 : l : 0,937
1 , 1 69 : l: 0,978
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ex
90° 29'
�
y
74° 13'
°
73
9'
69° 43'
71 o 3'
71 o li'
o
l
8 4 37
78° 13'
Låvenite:
6 [(Mn, Fe) (Ca, Na,) Si20ø]· 2� [ZrSi20ø] 2 [( Na.)2Zr2F.O.] ·l� [(Na., H.). (Zr, Ti)206]
·
Wohlerite:
6 [(Ca, Na2) Si206] [(Na2, H2).Zr2F.O,] · [Ca(Mg, Fe, Mn) (Zr, Ti, Si)206]· § [CaNb206]
•
Hiortdahlite:
6 [Ca2Si208] 2 [ ( Na2, Ca, H2)2Zr.F.04] § [Ca(Mg, Fe, Mn) (Zr, Ti, Si).06]
Rosenbuschite:
6 [CaSi03] 2 [Na2Zr02F,] [Ti(Si03) (TiOs)]
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Zeitschr. f. Krist. 16, 1890.
217
THE CHEMICAL FORMULA OF THE 'ZIRCON PYROXENES' ETC.
Chemical Analyses of the Zircon Pyroxenes.
Låveni te
Ceritoxides .............
CaO ............ .......
Na.o .. ................
MnO
.
. . .
. . .
FeO .... ...............
MgO
Zro.
1Nb, Ta).05
Fe203
Ti02
SiO•. . . . , . . . ..
..
H.o ..................
F
. .
lnsoluble Zircon . .
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O eq. 2 F
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6,93
11,23
7,30
3,02
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28,90
4, 13
0,78
2,00
29,17
0,65
3,82
3,08
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Wohlerite
l
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101,01
1,60
99,41
Låvenite
l
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26,95
7,50
1,00
1,26
0,12
16,11
Nb205 12,85
0,48
0,42
30, 12
0,74
2,98
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101,19
1,24
l
Rosenbuschite
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l
0,33
24,87
9,93
1,39
32,53
6,53
0,96
0,94
0,10
21,48
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20,10
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l
99,95
Wohlerite
Hiortdahlite
0,34
1,50
31,60
0,58
5,83
1,00
6,85
31,36
102,39
2,43
101,66
2,45
99,96
99,21
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5,83
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Hiortdahlite
l
Rosenbuschite
4
Cer Metals ..
449
579
482
Ca ......... 124
324
211
242
Na ......... 363
2
14
Mn
14
103
13
Fe" ..... ...
18
42
1061:4,05
1019:3,85
935:3,87
998:4,01
3
Mg .........
3
159
176
Zr .......
132
237
Nb Ta .....
31
92
13
4
Fe'"
10
6
. . .
93
19
Ti
25
5
Si .......... 487 487: 2,01 503 503:2,02 533 533: 2,03 524 524:2,00
64\
82 1
OH ........
72
1
F .......... 200 2176: 9,00 156 2242:9,00 305 2360:9,00 3Cl7 2358 , 9,oo
2051
1991
2004
0 .......... 1904
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f
f
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}
General formula: R4Si2X9 where R
Ca, Na, Mn, Fe, Mg, Zr, Nb, Ta, Ti
X=O,OH,F
Analysts: Låvenite
Wohlerite
Hiortdahlite
Rosenbuschite
l
=
P. T. CLEVE by W. C. BRøGGER, Zs. f. Krist. 16. 1890.
218
W. H . ZACHARIASEN
To the mineralogists of those days the above formulae seemed
to explain excellently the crystallographic agreement with Pyroxene
and Pectolite. BRØGGERS interpretation does not, however, match our
present knowledge of isomorphous substitution. We know f. ex. that
Na cannot be replaced by H, neither Si by Ti, Zr or Nb, nor any
ion by two ions with half the valence.
In the following I will try to interprete the chemical analyses
according to modern views of the isomorphous substitution.
We observe in the first place that the analyses contain no ions
which are able to replace silicon. We know further that O H and F
substitutes each other very easily and that these monovalent ions
may replace oxygen to a certain extent. This knowledge is sufficient
to enable us to deduce the chemical formula in a form RmSinXp,
where R represents all cations save silicon, and X the anions. This
is done in the tables, and we get as result the same general formula
for all four minerals, namely:
R4Si�X9•
We can write the formula better as:
R4Si207 (0, OH, F)2
It is, of course, possible that not all cations R replace each other
in the lattice, i. e. that they fall into two different groups, between
which isomorphous substitution does not take place. Without a com­
plete determination of the crystal structure we cannot give a definite
answer to this question, but it is my opinion that we can consider
all cations R as forming principally one constituent of the molecule.
From the above formula we see at once that no chemical rela­
tions to Pyroxenes or Pectolite exist. The names Zircon-pyroxene
and Zircon-pectolite have therefore no justification at all. A close
similarity in the crystal lattice cannot be expected, but it is just
conceiveable that the crystallographic relations to Pyroxene and
Pectolite are due to the fact that certain features (f. ex. in the arrange­
ment of the oxygens) in the structure may be common.
It would be a very interesting task to study the relations between
these 4 zirconiumbearing minerals themselves, and I hope in a later
paper to be able to give some information about this problem.
Oslo, Universitetets Mineralogiske Institut.
February 1930.
Printed, April 4th, 1930.