39

MODE OF ORIGIN

The supposed tabular form of the ore-body and its mineralogical
composition, in which garnet plays so important a part, suggest that the
mass is a replacement deposit. About 100 feet beyond the northernmost
exposure of magnetite there is a small, isolated outcrop of crystalline
limestone. It is possible that the magnetite body has replaced an extension
of this limestone, together with adjacent parts of the fine-grained extrusive
or intrusive voleanic rocks.

ECONOMIC CONSIDERATIONS

The shape and attitude of the ore-body are not definitely known. It
is apparent that the whole body is not iron ore, but the available exposures
are not sufficient to permit the forming of a reliable estimate of the pro-
portion of ore to waste material. In these circumstances the amount
of iron ore certainly known to be present is comparatively trifling.

A small amount of exploratory work would yield evidence which would
definitely indicate whether or not the ore-body is tabular, dipping to the
west. If, as is believed, this is the shape and attitude the possible iron
ore content may be considerable. The relations exhibited at the north
end of the outcrops suggest that the floor of the ore-body dips westward
at an angle not larger than 30 degrees and that the thickness of the deposit
is not greater than 25 or 30 feet. If, making allowances for a considerable
northward extension of the body beneath the drift, it be assumed that
the higher grade ore occupies a length of 250 feet and has an average
thickness of 25 feet, then the ore content for each foot in depth along the
plane of dip would be about 750 tons. The depth to which the body
may extend cannot be foretold, but may be no greater than the length
at the surface, say 250 feet, and the ore content would be, in round numbers,
175,000 tons. These figures are no more than an indication of the possible
order of magnitude of the ore-body, because the full length of the ore-body
at the surface has not been disclosed, its form and attitude may only be
surmised, and the-mode of distribution of ore within the mineralized body
is unknown.

(10 g) Jessie and Harriet Mining Claims, Harriet Harbour,
Moresby Island

(See Figure 5)

LOCATION

The outcrops of magnetite on the Jessie and Harriet mining claims
occur along the old trail from Jedway on Harriet harbour to Ikeda bay
and lie at elevations of 660 to 900 feet on the north-facing slope of a ridge
a few hundred yards east of where the trail crosses its summit. They
may be reached by following for three-quarters of a mile the new trail
from Jedway to Ikeda bay, to where the old trail branches and leads uphill;
the outcrops occur at a farther distance of about one-quarter mile along
the old trail.