HISTORY OF CRYSTALLINE ROCKS. 31 
layers, occasionally predominating, gives a stratified aspect to the iron ore. A similar 
ageregate is found in the Rideau district, in Ontario. 
§ 55. The stratiform character of these endogenous deposits, as seen alike in the 
individual portions, and in the arrangement of these as constituent parts of a vein, is well 
shown at the Union mine, in the Liévres district. Here the great mass or lode is seen to 
be bounded on the west by a dark-colored amphibolic gneiss, nearly vertical in attitude, 
and with a northwest strike. Within the vein, and near its western border, is enclosed 
a fragment of the gneiss, about twenty feet in width, which is traced some yards along 
the strike of the vein, to a cliff, where it is lost from sight, its breadth being previously 
much diminished. It is a sharply broken mass of gray banded gneiss, with a reéntering 
angle, and its close contact with the surrounding and adherent coarsely granular pyroxenic 
vein-stone is very distinct. Smaller masses of the same gneiss are also seen in the vein, 
which was observed for a breadth of about 150 feet across its strike,—nearly coincident 
with that of the adjacent gneiss,—and beyond was limited to the northeast by a consider- 
able breadth of the same country-rock. 
§ 56. In one opening on this lode there are seen, in a pect of forty feet of the 
banded veinstone, repeated layers of apatite, pyroxenite, and a granitoid quartzo-feldspathic 
rock, including portions of dark brown foliated pyroxene, all three of these being unlike 
anything inthe enclosing gneiss, but so distinctly banded as to be readily taken for 
country-rock by those not apprised of the venous character of the mass. A fracture, with 
a lateral displacement of two or three feet, is occupied by a granitic vein twelve inches 
wide, made up of quartz with two feldspars and black amphibole, which themselves pre- 
sent a distinctly banded arrangement. This same granitic vein is traced for fifty feet, 
cutting obliquely across both the pyroxenite and the older granitoid rock, and at length 
spreads out, and is confounded with a granitic mass interbedded in the greater vein. It 
is thus posterior alike to the older quartzo-feldspathic rock, the pyroxenite, and the 
apatite,—as are also many smaller quartzo-feldspathic veins, which, both here and in 
other localities in this region, intersect at various angles the apatite, the pyroxenite, and 
the granitoid rock into which the latter graduates. We have thus included in these great 
apatite-bearing lodes, quartzo-feldspathic rocks of at least two ages, both younger than 
the enclosing gneiss. A small vertical vein of fine-grained black diabase-like rock inter- 
sects the whole. No one looking for the first time at this section of forty feet, as exposed 
in the quarry, with its distinctly banded and alternating layers of pyroxenite and 
granitoid quartzo-feldspathic rock, including two larger and several smaller layers of 
crystalline apatite, would question the stratiform character of the mass, whose venous 
and endogenous nature is, nevertheless, distinctly apparent on farther study. 
In other portions of the same great vein, which has been quarried at many points, 
this regularity of arrangement is less evident. Occasionally masses are met with present- 
ing a concretionary structure, and consisting of rounded or oval aggregates of orthoclase 
and quartz, with small crystals of pyroxene around and between them ; the arrangement 
of the elements presenting a radiated and zone-like structure, and recalling the orbicular 
diorite of Corsica. The diameter of these granitic concretions varies from half an inch to 
one and two inches, and they have been seen in several localities in the veins of this 
region, over areas of many square feet. 
§ 57. In the Emerald mine the stratiform arrangement in the vein is remarkably 
