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porphyry is also the typical rock in the vicinity of Dak river where, par-
ticularly near Red Bluff and Washout creeks, it contains pyrrhotite as
well as pyrite. Much of the breccia of the area contains rock fragments
of the porphyry type and grades from extrusive, fragmental rocks to
crystalline intrusive rocks. An intrusive in the Copper Belt noted between
West Fork of Kitsault river and Evindsen creek may be very closely allied
to the feldspar porphyry. This rock is a syenite of granular texture and
contains orthoclase, some plagioclase of acid type, and also hornblende
and biotite. In the vicinity of Kinskuch lake are some finer grained
crystalline rocks that are probably lava flows. One such is purplish and
appears to be an amygdaloidal flow. Other rocks there are also very fine
grained but lack amygdules. These rocks may be very close to the feld-
spar porphyries in chemical composition.

The other main rock type is the augite porphyrite. Typically this
rock is studded with square augite phenocrysts about an eighth of an
inch across. The groundmass is typically light green and fine erained
but varies to darker shades. The rock occurs mainly on McGrath moun-
tain, but smaller bodies occur farther north. Most of the augite porphy-
rite contains much disseminated pyrite and some also contains much
pyrrhotite. The augite phenocrysts are in general quite unaltered. Most
of the augite porphyrite contains also phenocrysts of orthoclase and of
acid plagioclase. In all cases noted the feldspar phenocrysts are nearly
completely decomposed and in this respect contrast strongly with the
fresh augite. Hornblende also occurs as phenocrysts but is rather uncom-
mon except locally. Some of the porphyrite contains a fair amount of
apatite. The groundmass where identifiable consists in part at least of
very small crystals of acid feldspars and augite, but the eroundmass in
many of the specimens examined consists mainly of chlorite, sericite, and
calcite. One or more specimens hold chlorite amygdules and may repre-
sent flows. The corresponding breccias consist mainly of augite porphyrite
fragments in no way differing from the massive augite porphyrite. Pyrite
and pyrrhotite have been introduced into the breccias and in several
instances were noted to be associated with calcite in veinlets cutting the
rock and, therefore, appearing to have been introduced at a very late stage
in the alteration of the rock.

At the south end of the ridge west of LeRoy mountain a stock con-
sists of a rock rather closely allied to the typical augite porphyrite but
containing augite and orthoclase phenocrysts and also much biotite. The
rock resembles a granite in grain except for the augite and orthoclase
phenocrysts. The rock is an augite syenite having probably about the same
chemical composition as the augite porphyrite with which it is probably
closely related in origin, perhaps having come from the same general
magma reservoir.

Most of the tuffs and breccias are either of the feldspar porphyry
or of the augite porphyrite type. Many, though their mineral composi-
tion is the same as that of the feldspar porphyry, are purplish, whereas
most of the porphyry is grey to green. The purplish colour appears to be
chiefly due to red iron oxide in the cement between rock fragments. Some
of the felsitic tuffs consist mainly of rock fragments, others consist mainly
of crystal fragments, and all variations between the two extremes occur.