222

OCCURRENCE OF THE MAGNETITE

Magnetite occurs in a number of isolated pockets and lenses, strung
out in a northeast-southwest direction through a total distance of 770
feet. The main part of the prospecting has been carried out over 400
feet of this distance, and at a distance of 370 feet to the southwest the
last isolated deposit is found. The largest exposure of the better grade
of magnetite measures about 350 square feet in area, and the size of the
remaining ones is very much smaller. Elongated patches of rocky magne-
tite (magnetite mixed with a large quantity of contact metamorphosed
rock) up to 35 feet in length and 9 feet in diameter occur, but these also
are disconnected. Most of these outcrops are bounded by drift, so that
the relations of the individual occurrences are not clear, and their actual
sizes may be greater than their outcrops.

The western of the two tunnels crosses a contact between diorite and
limestone, but exposes only a small mass of magnetite in a drift to the
east. This tunnel demonstrates the lack of continuation between the
magnetite exposure 30 feet west of its portal, and the exposures around
the eastern tunnel.

CHARACTER OF THE MAGNETITE

Very little high-grade magnetite was seen either in place or on the
dumps. Most of it is intimately mixed with garnet, siderite, and calcite;
some of it is richly impregnated with chalcopyrite in grains and
stringers. é

ORIGIN OF THE DEPOSIT

The magnetite is clearly of contact metamorphic origin, and is the
result of the replacement of small elongated roof pendants of limestone
in the diorite, by the action of iron-bearing solutions derived from the
intrusive. The actual underground extent of these replacements has not
been determined, but there is nothing to indicate that they are of large
size.

ECONOMIC CONSIDERATIONS

The deposit is developed by considerable stripping, and open-cutting,
and by two tunnels, 100 feet and 35 feet in total length.

There are two selected analyses published by Lindeman and Brewer,
which are here quoted, simply to complete the descriptions.

— A B Cc
LrOn eye rete gangoapnooosnsodasonononeoaseoos 66-89 52-6 66-0
Phosphorus 9, esac eee eA eae nee 0-024 nil nil
Sulphursehsso suite ee eeeecee ee aeay ie eeeee ae ceeeere 0-060 4-2 trace
ANSOLUB Las tsciace tiene MR ote CRT TE ee ee 4-37 12-1 3-3
Coppercnayeccee ecco ee ee ee ee en era oe hd | eon ae 3-3

A. Lindeman, E.: Bibliography, No. 16, ‘‘average sample.”
B. Brewer, W. M.: Bibliography, No. 21, sample of ore from tunnel No. 2.
C. Ditto, ‘‘average sample from a large dump at the portal,”’ tunnel No. 1.

The deposit is of no value as an immediate source of iron ore.