70

outcrop was seen to extend downwards for at least a few feet on the inac-
cessible wall of the gully at whose edge the outcrop occurs.

Eastward from the Iron Duke claim, the upper slopes of the
high ridge rising on the north side of Fanny bay are partly occupied by
grey or white crystalline limestone and in connexion with this limestone
one or more outcrops of magnetite are said to occur. These were not
seen, but credible information was received that at least one of these occur-
rences was even less promising than the exposure on the lron Duke claim.
On the east shore of Phillips arm, opposite the mouth of Fanny bay, white
limestone is developed and it is stated that in places on the lower slopes
of the mountain outcrops of magnetite occur. On the ridge-like top of
the mountain, at an elevation of about 3,800 feet, crystalline limestone
forms the west end of the ridge; beyond, to the east, only diorite outcrops.
Near the contact of the two rocks a natural sink-hole in the limestone
shows on one side a mass of magnetite not over 44 feet wide admixed with
rock. Elsewhere in this pit and in a neighbouring pit are stringers and
masses, a few inches wide, of magnetite.

MODE OF ORIGIN

The various deposits of magnetite seen occur at or close to the contact
of granite or diorite with limestone or some bedded rock, and doubtless
all are connected in origin with the granitic rocks and are replacement
deposits formed after the period of plutonic invasion. In some cases they
replace limestone or other types of bedded rock, in other cases they partly
or wholly replace the diorite.

ECONOMIC CONSIDERATIONS

The magnetite occurrences seen on the Iron Duke claim, and those on
the summit of the mountain on the east side of Phillips arm, are so limited
in size as to appear to be of no economic importance except in so far as
they indicate that at least some of the conditions favouring the formation
of important bodies of magnetite were in existence.

On the Shoo Fly claim, the main tunnel penetrates a thickness of less
than 40 feet of mineralized rock. At the surface, 60 feet vertically above
the mineralized zone in the tunnel, mineralized rock outcrops, and pre-
sumably extends continuously for some considerable distance both to the
southeast and northwest, but the limited exposures do not disclose any
body of iron ore. In the second, higher tunnel, the amount of magnetite
is very small. The zone of altered and partly mineralized rock presumably
extends for a distance along or close to the limestone-diorite contact.
Several outcrops of garnetite were seen a considerable distance southeast.
Though the mineralized zone may have a considerable length, it is com-
paratively narrow. At the northwest end of the exposures, it is not more
than 30 feet broad, at the southeast end it may be 60 feet broad at the
surface, but a few feet vertically below the surface, in the higher tunnel, it
is less than half this width. The amount of magnetite is variable, so that
only limited portions are of the nature of iron ore. In the circumstances
it does not seem probable that any single large body of iron ore is present.
Even if the whole mineralized zone were magnetite ore, the tonnage present
for each 100 feet in depth would amount only to about 75,000 tons.