MICROPEGMATITE IN PURCELL BILLS. 
7 
of quartz was present in the slide examined. The secondary 
minerals consist chiefly of fibrous and non-fibrous hornblende. 
Sericite occurs as dust-like particles in the feldspars. The struct- 
ure of the rock is ophitic with the femic constituents filling the 
interstices of the lath-shaped labradorite crystals. 
A chemical analysis of a typical specimen of hypersthene 
gabbro is as follows : — 
Si0 2 
TiO* 
50-36 
.... 0-90 
13-63 
Fe,Oa 
2-22 
FeO 
8-38 
MnO 
... 0-20 
MgO 
8-67 
CaO 
11-50 
NaoO 
2-54 
KjO 
0-75 
H 2 0 + 
.... 0-05 
H 2 0 - 
0-71 
0-07 
99-98 
S.G 
2-970 
(M. F. Connor analyst). 
The norm calculated from this analysis is as follows: 
Orthoclase . . 
Albite 
Anorthite . . . 
Diopside 
Hypersthene 
Olivine 
Magnetite. . . 
Ilmenite 
4-44 
20-96 
23-63 
26-97 
9-86 
8-16 
3-24 
1-67 
Water 
98-93 
0-76 
99-69 
Hence in the quantitative classification the rock is auvergnose. 
