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.