181

avery short, thick lens. Since the deposit is clearly a replacement of an
inclusion of limestone, the latter alternative is decidedly the more plausible
of the two. Proceeding on the reasonable assumption that a body of such
a shape and origin will not be deeper than it is long, one arrives at the
figure of 125 feet as a plausible one for average depth. However, the
factor of depth, depending as it does on the shape of the original block of
limestone, may exceed this figure.

Analyses

As in the case of the Conqueror deposit, sampling was not done on
the Sirdar. The following analysis is taken from the available literature,
and is here introduced with its description, as giving some indication of
the grade of the deposit. It is hardly probable that the entire body of
magnetite outlined on the map would analyse as low in sulphur as the
figure given herewith.

A
TON. eyes 56-57
Insoluble.. 8-52
Sulphur... 2-75
NAITO RDHOLUSs see tem te eee rey pamieh Rates solution me acce weee aE 0-121

A. Lindeman, E.: Bibliography, No. 16. Average sample taken along the tunnel.
Tonnage Estimate

Insufficient development of the deposit prevents any reliable estimate
of tonnage, but the following data are offered as indicating an approxima-
tion to the size of the body of magnetite.

Proved Ore: Ore included within the volume, having as the outline of
its top surface the exposed margin of the deposit, as its southwest boundary,
a 70 degrees-dipping contact, and as its bottom surfaces an inverted gable,
the axis of which is the horizontal centre line of exposed ore in the tunnel.
This volume is considered as two pyramids, base to base, with heights of
60 feet to the northwest and southeast extremities of the magnetite exposure,
the area of the base being that of the magnetite shown in the cross-section
through the tunnel. 2,000 (area of section in square feet) X 60 (height in
feet) + 3 (for volume of pyramid) X 2 (number of pyramids) + 8 (cubic
feet per ton) = 10,000 tons.

Probable Ore: Ore contained within the volume of an irregular prism
with a dip of 60 degrees to 70 degrees, whose base is on the tunnel level
with an area equal to the area of exposure of magnetite on the surface, less
the figures for proved ore given above. 6,100 (square feet, area of base)
26 (average height) + 8 (cubic feet per ton) = 19,825 tons. 19,825 —
10,000 (proved ore) = 9,825 tons of probable ore.

Possible Ore: It is out of the question to give any worth-while estimate
of possible ore. It might be stated, however, that, for every 100 feet of
depth with the area of present exposure of magnetite (6,100 square feet)
there would be an additional 76,250 tons. This figure, or any extension
vertically, is considered as highly speculative.

Value of Sirdar Deposit

Considered as a single isolated occurrence this deposit is of no economic
value. It is more reasonable, however, to view the Sirdar deposit as one
of a group of magnetite bodies situated along Bugaboo creek and to esti-
mate its value from this standpoint (See page 177).