98 
VICTORIA MEMORIAL MUSEUM. BULLETIN NO. I 
These figures afford the following molecular ratios: — 
SiOi 
AI2O3 FesOs 
CaO 
HaO 
0-739 
0-188 0-041 
0-454 
0-222 
0-739 
0-229 
0-454 
0-222 
3 
1 
2 
1 
(+ 0-073). 
The excess of 0 * 073 in the molecular ratio probably represents 
admixed quartz which would thus amount to 4*38 per cent. 
By subtracting this from the total silica and recalculating the 
remaining constituents the centesimal composition of the min- 
eral is obtained. This is given in column I; the figures in 
column II are those obtained by Genth (American Philosophical 
Society, XX, 401, 1882) for another prehnite high in iron from 
Cornwall, Pennsylvania; these are added for purposes of com- 
parison. 
I. 
II. 
Silica (SiOa) 
42-40 
Alumina (AI 2 O 3 )... 
20-36 
20-88 
Ferric oxide (FesOs) 
5-54 
Calcium monoxide (CaO) 
26-70 
27-02 
Water (HsO) 
4*19 
4-01 
100-00 
99-85 
Owing to its high iron content it has been suggested by 
Professor Pirsson that this variety of the mineral be called 
ferroprehnite. 
