HISTORY OF CRYSTALLINE ROCKS. 27 
phlogophite, orthoclase, quartz, and calcite, and that of the interstratification of the same 
apatite, in contemporaneous layers with a gneissoid pyroxenic rock, for the reason that 
both statements are strictly true, and that in their reconciliation light will be thrown on 
the great problem of the genesis of these crystalline aggregates. The mining operations 
on a large scale in these apatite deposits in the Liévres district, especially in the years 
1883-1885, have in fact shown that the stratiform pyroxenic masses are, like the associated 
orthoclase-rock, the apatite, and the calcite, subordinate parts of veins, which assume in 
many cases vast proportions, and at the same time have in parts of their mass a banded 
structure much resembling that of the enclosing gneiss. Illustrations of this condition 
of things abound at the great open cuttings for exploration and for mining which have 
been made at the High Rock, the Union, and the Emerald mines, in Portland and Buck- 
ingham townships, on the Liévres River.' At the first-named locality the nearly ver- 
tical gray hornblendic gneiss, running northeast and southwest, is traversed by venous 
masses, sometimes with the strike, but at other times oblique or even at a right angle. 
§ 47. A study of some of the smaller veins of the region (which are not mined) will 
help to an understanding of the nature and relations of those which are exploited for 
apatite. As seen at the High Rock mine, these lesser veins are from a few inches to 
several feet in width, and are chiefly of a binary granite or pegmatite, often including 
portions of the wall-rock, and sometimes, near their borders, presenting, for a breadth of 
two or three feet, a veritable breccia of angular fragments of gneiss from one to six inches 
in diameter. The granitic veinstone includes two feldspars, one weathering white and 
the other reddish, the latter forming considerable cleavable masses. A little white mica 
is also sometimes met with in these veins, which, in parts of their extension, hold portions 
of green cleavable pyroxene, sometimes in slender strings running with the strike, but in 
other cases filling the greater part of the vein, and including little seams of white felds- 
par, and small masses of greenish apatite,—fine and large crystals of which, and others 
of pyroxene, are, moreover, occasionally found directly imbedded in the granitic vein- 
stone. 
§ 48. Veins of vitreous quartz a foot or more in breadth are met with in the imme- 
diate vicinity, and also sometimes enclose crystals of apatite, or portions of feldspar, by an 
admixture of which they graduate into the binary granite or pegmatite. There is thus 
apparent a transition from pure quartz to a granitic rock, and to one essentially 
pyroxenic, each occasionally bearing apatite, which of itself also forms rock-masses. All 
of these are associated in the larger veins, in alternating bands or irregular lenticular 
masses sometimes a few inches in thickness, but at other times attaining breadths of many 
feet each. A frequent intermediate type of rock in these veinstones consists of a granular 
or coarsely cleavable green pyroxene with an admixture of quartz, and a feldspar, gene- 
rally white in color, but occasionally bluish, and with cleavage-planes an inch in breadth. 
The quartz and feldspar in this aggregate sometimes predominate, offering a transition 
into the granitic rock already noticed, which frequently includes crystals of pyroxene, 

" The workings at each of the three mines named have yielded five thousand tons or more of commercial 
apatite annually for three or four years, and consist for the most part of open cuttings, in some cases to depths of 
over one hundred feet, causing the uncoyering or displacement of great portions of the accompanying rock-masses. 
In other mines in this region, also very productive, shafts have been sunk on apatite bands in these veins to 
depths of one hundred and fifty and two hundred feet. 
