164

B. Limonite Deposits

West arm, Quatsino sound

C. Segregation or Shear-zone Deposits in Gabbro

Sooke peninsula

D. Beach Placers
Wreck Bay black sand deposits

SUMMARY OF THE DEPOSITS WITH TONNAGE
ESTIMATES

In submitting the following estimate of available iron ore in the west
coast deposits, it is hoped that the reader will bear in mind the following
facts on which all the conclusions are based.

(1) “Proved ore’’ is used in the sense adopted by mining organizations,
who"’may be contemplating the investment of capital in mining and treat-
ment plants. By it is meant a body of ore that is exposed either by nature
or by artificial development, or both, on three sides, to such an extent that
there is no question of its actual existence.

(2) “Probable ore’ is used partly in a commercial and partly in a
geological sense, to mean ore whose existence is strongly indicated but not
proved, in that it is not exposed on three sides. It applies particularly to
the probable extension of exposed masses or ledges and is usually based on
a generally accepted geological principle that in the average case a body
of ore will continue in depth to a distance equal to at least half of its surface
length.

(3) “Possible ore” is used to indicate a possible extension of exposed
bodies beyond the limits of what is included in probable ore, and in some
sense to include deposits that may not outcrop at the present surface.
It is quite evident that calculations of tonnage founded on such a delicate
basis of fact could not, and would not, be included by any reliable mining
company in any valuation of a deposit, except in so far as they would affect
its speculative value. It was found to be so difficult, indeed almost impos-
sible, to establish the geological limits of what might be included under
the term ‘possible ore,’ that in most cases, the writer has preferred to
present figures for such a tonnage in terms of various assumed figures for
depth or sidewise extension. For instance, the statement concerning
possible ore may be made in this manner, namely, that for every 100
feet of additional depth with the same area of surface exposure, there
would be included, say, 60,000 tons of ore. Such a statement gives a
concept of magnitude to the deposit that is useful, but it does not signify
an actual extension to 100 feet, nor does it indicate the geological possibili-
ties of such an extension.

(4) The reason for the conservative basis of estimation outlined
above is that the main deposits are of contact metamorphic origin; and it
is a well-established geological fact that deposits of this type are extremely
prone to be irregular, freakish, to change grade rapidly, to pinch or swell
to a marked degree in short distances, and to be subject generally to a
well-known set of idiosyncrasies.