CLARKE.] 
NORMAL ZEOLITES. 
37 
Calculating for mixtures in the ratios of 1 : 1 and 2 : 1, we get from these 
formula} the following composition of gmelinite, in comparison with 
analyses by Kammelsberg and by Pirsson : * 
Rammels- 
berg. 
i 
Pirsson. j 1:1. 
2:1. 
SiOo 
46.48 
20.64 
50.67 
18.50 
.15 
1.05 
9.88 
.16 
20.15 
46.89 
19.92 
50.89 
18.21 
AL0 3 
Fe,0 3 
CaO 
3.78 
7.19 
1.74 
20.41 
1 
} 12. 11 
J 
21.08 
11.27 
19.63 
Na,0 
K-0 
H 2 
100. 24 
100. 56 
100. 00 
100. 00 
The water is probably all crystalline, thus distinguishing gmelinite 
from a sodium chabazite; but the evidence on this point is incomplete. 
Pirsson's analysis may also be represented by a mixed_salt of this char- 
acter : 
,Si0 4 =Na 3 
Al-Si 3 O s =Al +9H 2 
\si 3 8 =Al 
indicating a relationship to analcite. Such a relation is suggested by 
the experiments of Leinberg, t who not only derived analcite from the 
zeolites of this group, but also, starting from fused analcite, obtained 
a compound approximating to gmelinite in composition. 
For chabazite the fundamental ratios are essentially the same as with 
gmelinite, but the proportions between lime and soda vary greatly. 
Potassium is also present to a noteworthy extent in some cases, indicat- 
ing a partial derivation of the mineral from leucite, orthoclase, or inicro- 
cline. As regards hydration, a part of the water in chabazite appears 
to be constitutional, probably two molecules out of the nine shown in 
the gmelinite formula, but this point is not absolutely certain. The 
evidence in its favor is strong, but not conclusive. 
The analyses of chabazite are numerous. Some of them reduce easily 
to mixtures of anorthite+18 aq. and albite-J-9 aq., and some, show- 
ing little lime, represent isomers of gmelinite. But many chabazites 
are very low in alkalies, while the ratio between Si 3 O s and Si0 4 remains 
practically constant. In these cases it seems necessary to assume the 
existence of a trisilicate anorthite, or calcium albite, which, by itself, 
is not known in nature. According to Doelter,f chabazite yields upon 
fusion a mixture of anorthite and silica, a fact which is in harmony 
* Daiia, 6th cd., p. 594. 
t Zeitsch. Geol. Gesell., 1885, p. 972. 
J Allgern. Cheni. Mineralogie, p. 183. 
