. The sampling and estimation of ore in a mine . count of the history of the property and itsprevious underground development. He will, however,be likely to exercise unusual caution in estimating thethree classes of positive, probable and possibleore, when dealing with a class of deposits which aregenetically connected with the chemically induced re-placement of limestone by metallic sulphides. In the accompanying diagram (plan) the ore-body rep-resented is an occurrence in a limestone bed, say, 7 The bed, itself lying flat, is heavily carbonate of lime has been repla
. The sampling and estimation of ore in a mine . count of the history of the property and itsprevious underground development. He will, however,be likely to exercise unusual caution in estimating thethree classes of positive, probable and possibleore, when dealing with a class of deposits which aregenetically connected with the chemically induced re-placement of limestone by metallic sulphides. In the accompanying diagram (plan) the ore-body rep-resented is an occurrence in a limestone bed, say, 7 The bed, itself lying flat, is heavily carbonate of lime has been replaced by metallic sul- -98— AND ESTIMATION OF ORK IN A MINE phides carrying values. The enclosins^ beds, namely,those lyini^ above and below, are barren, and the min-eralized bed itself contains barren patches, sporadicallydistributed. Assume that the ore-body thus defined, aportion of which is here represented, had dimensions asfollows: Seven feet thick, that is the thickness of thelimestone stratum, 150 ft. long and 90 ft. wide. The. Plan of a Part of the Workings of a Silver-LeadMine in Horizontally Redded Limestone. four tunnels represented are all run in this ore-body,and by their intersections enclose a portion of it, A BC D. In other words, a block of ore is exposed on foursides, 7 ft. thick, 45 ft. wide, and 70 ft. long. If oneshould apply an arbitrary rule of sampling in the ex-amination of the mine in which this case occurs, the orein question must be classed under the head of not questioning the correctness of his classifica-tion, I have endeavored to show, by the diagram, theerror to which the examiner would be liable, should heestimate the block represented by A B C D as ore. Onthe other hand, if the examiner takes into consideration SAM»M,1N(. ANI> I SI IM A IK^N OF OKE IN A MINK the g^eological principles on which the class of limestonesilver-lead deposits depends, he will probably allow inhis calculations for the possibility of the p
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