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matrix, differing from the fine conglomerates only in the size of the larger
grains, to fine, metamorphosed siltstones and sandy argillites; and from
extremely pure orthoquartzites to rocks in which quartz makes up less
than 50 per cent of the total volume. With the exception of the ortho-
quartzites, almost all of the quartzites of the Ingenika group appear to
have originated as “subgreywacke” (Pettijohn, 1949, p. 255), that is, as
sandstones containing less than 15 per cent feldspar with a cement that is
equivalent in composition to a slate. A few beds contain enough feldspar
to be classed as true greywacke. Rocks of this type grade, with apparently
about the same mineral assemblage, from the conglomerates already
described to fine argillites and slates by a simple decrease in the amount
and coarseness of detrital quartz and feldspars. In the Espee Range some
beds are so little metamorphosed that they may be called greywacke and
subgreywacke (See section page 81).

The purest quartzites, such as the conspicuous group of white beds
exposed on Ingenika Cone, Barrier Peak, and in the Russel Range, are
composed of rounded single quartz grains, or fragments of vein quartz or
quartzite, in a more or less crystalloblastic, very fine-grained, siliceous
matrix (See Plate VII B). The size of the larger grains varies from 0-1 to
1-0 mm., but in any one bed the sorting and degree of rounding of the
grains are excellent. The degree of recrystallization varies considerably; in
the purest white quartzites the entire rock has been recrystallized, with a
uniform crystalloblastic texture.

Schists, Phyllites, Slates, and Argillites

The fine-grained clastic sediments of the Ingenika group rocks differ
from the impure quartzites only in a finer grain size and lesser relative pro-
portion of detrital quartz and feldspar, and a corresponding increase of
argillaceous material. All gradations are represented between quartzites
and metamorphosed subgreywackes and slates whose texture is too fine
grained to enable the mineral constituents to be determined microscopically.
Most of the slaty rocks are of about silt grade; the extremely fine-grained
rocks are found chiefly in thin beds intercalated with limestones. Most
commonly, these rocks have been metamorphosed to slaty phyllites; in a
few upper beds the recrystallization has been minor and the rocks are
normal, highly indurated argillites; other beds have a well-developed slaty
cleavage, and many of the lower beds are fine- to medium-grained quartz-
chlorite-sericite schists.

On the crest of Espee Range, near the north border of the map-area,
impure slaty limestones and phyllites have been deformed around lenses and
pod-like bodies up to 50 feet by 30 feet of an unusual, green, finely granular
material. The ‘pods’ are not confined to one stratigraphic horizon, but
make up about one-tenth of the rock volume in a stratigraphic interval of
about 100 feet, over an exposed length of 4 mile. In thin section, this rock
appears to have had an originally coarse inequigranular texture, but it is
now composed of a confused aggregate of colourless and green grains con-
taining abundant minute rod-like bodies. The colourless grains have a
tabular to radiating habit, an average refractive index of about 1-565 to
1-570, a relatively low birefringence, parallel or nearly parallel extinction,
and are optically length-slow. They are tentatively identified as antigorite,
and occur more or less evenly distributed through the rock with fairly well

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