89 
THE APATITE DEPOSITS AT THE EMERALD 
MINE. 
LocAaL GEOLOGY. 
The hill containing the Emerald and Squaw Hill 
groups of mines rises abruptly from the plain of Leda 
clay and abuts on the left bank of Lievre river. This 
proximity to the river facilitated shipmen of the phos- 
phate by water to Buckingham, when the mines were 
producing. 
Grenville limestone, the oldest of the rocks found 
in this locality, is represented by small remnants of much 
altered and very impure limestone. Garnetiferous and 
sillimanite gneisses situated west of the main occurrences 
of gabbro may represent an argillaceous phase of the 
Grenville series, though richness in aluminous silicates 
is about the only evidence of their sedimentary nature. 
The older gneisses to the east of the gabbro area are for the 
most part hypersthene-granites rich in quartz. They 
include garnetiferous bands, and often garnet entirely 
replaces the pyroxenes, resulting in rocks comparable to 
the leptynites of French authors. These rocks so closely 
resemble the charnockites of southern India in their general 
character and age, that the name charnockite is applied 
here, due weight being given to Holland’s warning regard- 
ing the application of this term outside of India. 
The older rocks of the above groups have been intruded 
by binary granite, and again by a younger series of gabbros 
and diorites, of which the last named often have the form 
of lenticular dykes. After microscopical study, there 
appears to be no reason for differentiating these gabbros 
from each other. Therefore they have received one colour 
on the map. A later series of pegmatites has cut these 
and all older rocks, and the pyroxenite dykes carrying 
the apatite deposits are later than the pegmatites. It 
has been usual in the past to associate the pyroxenite 
dykes with the gabbros above mentioned and no evidence 
contradictory to this opinion has appeared as yet; hence 
it is probable that these later pegmatites are closely 
connected in origin with the gabbros, perhaps as acid and 
basic differentiation products of one parent magma. 
The youngest Pre-Cambrian rock in the area is a 
50 foot (15-2 m.) dyke of olivine-diabase, which cuts all 
