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Although not proved, it is believed from other studies in Barkley
sound that the granitic intrusive is of later date than the diorite, and
may even be found to cut the magnetite. As shown by the geological
map of the west coast of Vancouver island, mentioned above (page 206),
diorite is the principal country rock, including limestone as roof pendants,
and traversed by dyke-like- bodies of the more acidic granodiorite and
allied types.

OCCURRENCE OF THE MAGNETITE

Magnetite occurs, mixed with highly metamorphosed, fine-grained
rock, in a prominent bluff facing south. There is no body of magnetite
in the entire outcrop pure enough to map as such, so that the deposit is
outlined as ‘magnetite mixed with gangue”. Fine-grained dyke-like
stringers and irregular masses of aplite occur in places within the magnetite.
The lode is confined by bedrock walls along its easterly margin where it
is in contact with a garnetized phase of granite, and along a small part of
its northwest edge where it lies against a small exposure of hornblende
diorite.

The attitude or structure of this deposit is not clear. In the face of
the bluff there is a rude interbanding of magnetite and rock, that appears
to give the lode a dip to the south parallel to the slope of the hill. If this
dip were less than 24 degrees the lowest exposure of magnetite at the
bottom of the bluff would in its southerly extension pass over the portal
of the tunnel. This would appear to be the probable solution of the struc-
ture, since, as stated by Brewer (21, pages 26-27), ‘‘an adit is driven 72 fect
into the bluff under the outcropping, about 40 feet vertical measurement
below the top, and at the face a drift is driven 45 feet to the right. No
magnetite is exposed by this work, which confirms the blanket-structure
theory’. The portal of the tunnel was in a caved condition in 1924, making
access impossible, The dump was observed to contain fragments of the
rocks exposed around the lode, but no magnetite.

CHARACTER OF THE MAGNETITE

The outcrop of the deposit is very rusty, due to oxidation of sulphides
which are quite abundant; the mixture with rock is on such a scale
as to reduce the content of magnetite to about 50 per cent of the whole.
The magnetite itself is very much fractured, and crumbles into small
pieces readily.

ORIGIN OF THE DEPOSIT

The deposit is believed to be of contact metamorphic origin and to
have been developed in a flatly dipping series of tuffs under the influence
of intrusive hornblende diorite. The evidence for this hypothesis of
origin is partly taken from the deposit and is partly based on a compara-
tive study of similar occurrences. The low dip, the bedded structure, and
the general impurity and mixture with rock, suggest a similarity of this
type with the replacement of bedded tuffs at the Crown Prince and on
Copper island, although unaltered or at least recognizable tuff was not
found to occur in the proximity of the outcropping. Limestone is exposed
in two places, but in neither place does it contain any magnetite nor is
any limestone found, even in fragments, associated with the magnetite.