IOI 
THE GRAPHITE DEPOSITS AT THE WALKER 
MINE. 
GENERAL GEOLOGY OF THE LOCALITY. 
Grenville limestone, the oldest Pre-Cambrian rock in 
this locality, occurs on the hill above the smaller mill- 
pond and to the south of the larger pond. Also, in the 
northwestern part of the area it is represented by a broader 
band which extends in a direction somewhat east of north. 
This limestone band is flanked on either side by Ottawa 
gneiss, the most important member of which is a quartz- 
rich variety, very similar in appearance to the hypersthene- 
granites of the Emerald mine. Small graphite bodies are 
occasionally seen in this gneiss, more especially on joint faces 
Pegmatitic phases are developed in the extreme north- 
western corner of the area. Small amounts of para- 
gneisses may be included in this igneous complex, but as 
yet none have been definitely recognised. 
The larger part of the map area is occupied by more 
basic varieties of Ottawa gneiss than those just described. 
They consist of gabbros and diorites with pyroxenite, 
amphibolite, anorthosite, and hypersthene-gabbro basic 
variations. Scapolite is of common occurrence in these 
basic gneisses, which appear to be younger than those 
described above. In the northern part of the map area 
a younger gabbro has been separated from the other basic 
gneisses, but otherwise the relative ages of the intrusions 
constituting the basic part of the complex remain unknown. 
At a distinctly later period in Pre-Cambrian time, the 
Grenville limestone and Ottawa gneiss were invaded by 
pegmatite, diorite and gabbro dykes, which probably 
represent more than one magmatic intrusion. The graph- 
ite ore bodies are always found in close association with 
these dykes. One of the pegmatite dykes has graphite 
distributed throughout its mass in great abundance. 
GEOLOGICAL RELATIONSHIPS OF THE GRAPHITE DEPOSITS. 
The main pit is situated at the foot of a cliff, which, 
from top to bottom, consists of biotite-diorite-gneiss, a 
horizontal dyke or sheet of biotite-diorite from 6 to 20 
feet (1-8 to 6-I m.) in thickness and a much altered lime- 
stone. Immediately to the south the limestone is also 
