* 
of some American Minerals. | Al 
mineral. Otherwise, substituting soda for magnesia, his analy- 
sis agrees pretty nearly with the one given above, which was 
done under my direction by Mr. J. S. Kendall. Hayes had 
also analyzed this mineral, and corrected Beck’s analysis as ` 
far as relates to the absence of magnesia, and the presence of 
soda. He however did not find that it contained water, which 
is essential to the composition of pectolite. 
IV. is also a fibrous mineral from Bergen Hill, which evi- 
dently agrees in composition with pectolite. It differs from 
the other specimen from the same locality, in its fibres being 
straight and not grouped together into star-like forms. This 
analysis was executed at my request by Mr. G. J. Dickinson. 
It is evident that these minerals all agree in chemical com- 
position with the pectolite of Von Kobell, and also in external 
characters. Slight differences in the results of the analyses 
may easily be accounted for by the difficulty of procuring a 
finely fibrous mineral in a state of known freedom from inter- 
mixture with foreign substances. 
The formula given by Von Kobell for Pectolite is 
3 Na Si + 4 Ca? Si? + 3 H 
Which formula requires 
Silica 59.55 
Lime 34.94 
Soda 9.70 
Water 2.79 
99.98 
Frankenheim considers the water in the pectolite as un- 
essential, and allies this*mineral with the Augite family, from 
which it differs widely in chemical characters. The constant 
Presence of nearly 3 per cent. of water in all the analyses of 
the substance dried at 100° C., makes it highly improbable 
that it should be merely accidental. In fact, the formula 
given above seems to be the only one which could be adopted 
for this mineral. 
JOURNAL B. S. N. H. 6 
