Structural Relations.

Highly jointed, sheared and broken,
veined with calcite and quartz,
and brilliant jasper.

Columnar joints, and _ otherwise
jointed but not to such an extent
as the Yakoun formation.

(See also page 80.)

Lithological Character.

Basalt and andesite tuffs and agglom-

erates. Rarely diabase.

Basalts, agglomerates, and tufts.

Middle Colour.

Purplish, greenish, blackish, and
dark grey; altered looking, and
stained with epidote, chlorite, and
limonite. A dull, mottled pur-
plish and green tint is very com-
mon.

Dark grey or black; usually fresh
looking and unstained. Agglom-
erates often rusty.

Texture.

Typically fragmental rocks, tuffs,
and very dense agglomerates.
Fragments angular, and of all
sizes up to several feet. In some
cases well bedded, in layers of
varying thickness. Dense, por-
phyritic, and amygdaloidal flows,
and injected rocks are found. Fre-
quently highly porphyritic.

Typically massive, dense, devitrified
or sparingly porphyritic flow rocks,
occasionally amygdaloidal. Frag-
mental rocks are abundant, and a
few bright red interstratified clay
sediments are found. Columnar
structures common. Agglomer-
ates loose textured.

Microscopic.

Essential minerals: labradorite,
AbssAngs-AbsoAnso; more rarely-
andesine; augite. Subordinate
minerals: magnetite, titanite,
rarely biotite. Secondary chlorite,
calcite, etc.

Essential minerals: labradorite,
AbsoAnz-AbsoAns0; augite. Sub-
ordinate minerals: magnetite.
Secondary minerals: chlorite, cal-
cite, epidote, etc.

Microscopic Texture.

Wholly crystalline, finely even gran-
ular or porphyritic; feldspar
equidimensional; texture inter-
sertal or ophitic; flow structure
rare.

Wholly or partly crystalline; finely
even granular, frequently por-
phyritic; feldspar markedly lath-
shaped; texture intersertal, rarely
ophitic; highly developed flow
structure universal. Vitreous
rocks found.

Ra RAE aR