Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . posed on two sides.()re Developmgj Possible Ore 1 The whole or a part of the ore below theOre Expectant J lowest level or beyond the range of vision. No two of these parallel expressions mean quite the samething; each more or less overlies into another class, and in factnone of them is based upon a logical footing for such a classifi-cation. For example, values can be assumed to penetrate somedistance from every sampled face, even if it be only ten feet, sothat ore exposed on one side
Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . posed on two sides.()re Developmgj Possible Ore 1 The whole or a part of the ore below theOre Expectant J lowest level or beyond the range of vision. No two of these parallel expressions mean quite the samething; each more or less overlies into another class, and in factnone of them is based upon a logical footing for such a classifi-cation. For example, values can be assumed to penetrate somedistance from every sampled face, even if it be only ten feet, sothat ore exposed on one side will show some positive or de-veloped ore which, on the lines laid down above, might be 18 PRINCIPLES OF MINING. probable or even possible ore. Likewise, ore may befully developed or blocked out so far as it is necessary forstoping purposes with modern wide inteivals between levels,and still be in blocks too large to warrant an assumption of con-tinuity of values to their centers (Fig. 1). As to the thirdclass of possible ore, it conveys an impression of tangibility ^;j!Bw^jT>^;v«j^^>^-!J<*<. Fig. 1. — Longitudinal section of a mine, showing classification of the exposed , 400 feet = 1 inch. to a nebulous hazard, and should never be used in connectionwith positive tonnages. This part of the mines value comesunder extension of the deposit a long distance beyond openings,which is a speculation and cannot be defined in absolute tonswithout exhaustive explanation of the risks attached, in w^hichcase any phrase intended to shorten description is likely to bemisleading. Therefore empirical expressions in terms of developmentopenings cannot be made to cover a geologic factor such as the MINE VALUATION. 19 distribution of metals Through a rock mass. The only logicalbasis of ore classification for estimation purposes is one whichis founded on the chances of the values penetrating from thesurface of the exposures for each particular mine. Ore that maybe calculated
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