11

able development of actinolite in places; a general silicification bound
the whole mass together again, and filled the interstices with quartz. The
result then was veins, with fairly definite walls which were parallel in
general but not in detail, which bulged and contracted both horizontally
and vertically to include the brecciated and partly ground-up country rock
(granodiorite), or followed relatively narrow and definite lines where the
rock was not shattered. The filling in the wider parts would then be of
fragments and debris of the original rock, partly or in places wholly
replaced by actinolite and quartz in varying amount, whereas the narrower
parts contained similar material but no fragments, so were much tighter.

The second fissuring followed the same lines as the primary, but in
this case the fissured rock was not homogeneous as at first, so that the
fissure had a different expression in passing through the different gangue
materials or combinations of them. In the strongly cemented, narrow
portions the fracturing seems to have made a relatively clean break either
in the vein or along one of its walls, showing that the vein in those portions
acted as though it were part of the general country rock. In the hetero-
geneous portions of the vein the fissuring spread, giving the effect of
crushing. j

The ore-bearing solutions followed the second fissuring, and naturally
found easy passage through those parts of the veins which had been
crushed most by this fissuring; these places were also the loci of the greatest
deposition of actinolite and of crushed and altered country rock, both of
which were apparently easily replaced by the ores.

The primary cause of the larger portions of the vein is not evident.
They may have been partly due to differential movement of the irregular
walls of the fissure, otherwise it is not clear why certain portions of the
eranodiorite should have suffered brecciation and why others, apparently
similar, broke with a clean fracture. This point seems to be the ultimate
determining factor in the location of the ore-shoots.

Paragenesis of the Ores. General. There were two distinct mineraliza-
tions in the veins on this property. Their sequence can be established,
but the lapse of time between the depositions is not readily determinable.
The first mineral group bears a close relationship to that of the Delta
property, but is distinctive in having a considerable development. of
arsenopyrite and of pyrrhotite instead of the abundant magnetite and
hematite of the Delta occurrence. The other minerals are the same in
each.

In position the Rocher De Boule veins are nearer the contact of the
granodiorite with the sediments than are the Delta veins and apparently
represent a progressively cooler phase of the deposition, the hottest portion
of which would be expected in the interior of the granitic mass where the
Delta property is located.

The ore from the veins of the Rocher De Boule mine is chiefly valuable
for its copper content, though paying quantities of silver and gold are also
present. Besides these metals, large amounts of iron, lead, zine, and
arsentc, and smaller quantities of antimony and molybdenum also cccur,
but none of them is worth extracting

These metals are combined in the following minerals: chalcopyrite,
which forms the bulk of the ore; pyrite, pyrrhotite, arsenopyrite, tetra-
hedrite, zinc blende, galena, which may be seen in almost all hand specimens,
and magnetite and molybdenite which are only rarely seen.

57091—3