142 On the Chemical Composition of Wernerite, 
nal Wernerite, from which the pseudomorphous epidote was 
produced, had a composition represented by the formula of 
meionite; for with the exception of the mineral from Vesu- 
vius, no Wernerite is known whose composition approaches at 
all near to it. 
The only possible inference therefore, is, that the change 
has been effected by a substitution of the constituents of a 
scapolite. In order to clear up this point, an analysis was 
made of a scapolite resembling the prismatic scapolite (7), 
which had been partially converted into epidote :— 
I. Ti. Ti. 
Silica, : 43°41 46:82 37.92 
Peroxide of iron, 8°68 1:39 15°55 
Potash, i 0°72 0:97 80-23 
Soda, 3°24 6:88 0:39 
A mixture of equal parts of the scapolite (7) and epidote, 
would give an analysis :— 
Silica, ‘ " ‘ ; ’ P 49°37 
Peroxide of iron, ; ? D \ 8:47 
Paveh, ) d ; ; : : 0°60 
Soda, : : : : : : 3°63 
Numbers which correspond very closely with I. 
There can be little doubt, therefore, that the pseudo- 
morphous epidote was produced by chemical alteration of the 
scapolite substance. Now, it is customary to assume that 
when a calcareous mineral suffers alteration, the result is an 
abstraction of lime, and a relative increase of silica. But 
this pseudomorphous epidote presents an example of the 
contrary; the percentage of silica is less, that of lime 
greater. The larger proportion of lime cannot be ascribed 
to an abstraction of other constituents ; it must have been 
actually introduced, for the epidote mass is compact, free 
from cavities, and appears perfectly homogeneous. 
From the results of this and previous investigations of 
Wernerite, the following conclusions may be drawn as to its 
chemical history :— 
I. With regard to the normal constitution, there appears 
to be several heteromeric species :— 
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