Transactions . small stringers or bands of quartz which areoften mistaken for veins or lodes. In many places these schistsare cut by andesites and porphyry dikes, which might havesomething to do with concentrating the gold. The gold doesnot occur disseminated through the quartz stringers, as mighthave been expected, but is found on the contact between thequarts and the Bchists. These quartz pebbles, of which the gravelsmainly consist, contain little or no gold, so that what cannot berecovered by placer or gravel mining would not pay to lode mine. There are aeveral met hods of prospecting in vo
Transactions . small stringers or bands of quartz which areoften mistaken for veins or lodes. In many places these schistsare cut by andesites and porphyry dikes, which might havesomething to do with concentrating the gold. The gold doesnot occur disseminated through the quartz stringers, as mighthave been expected, but is found on the contact between thequarts and the Bchists. These quartz pebbles, of which the gravelsmainly consist, contain little or no gold, so that what cannot berecovered by placer or gravel mining would not pay to lode mine. There are aeveral met hods of prospecting in vogue in the Yukon,and the ri<dit one to be used in a particular case depends on theextent and position of the ground and the character and depthof the overlying -oil. 552 The Canadian Mining Institute The following is a list of the methods most generally used:—Adits, open cuts, drill holes, shaft sinking. An attempt will bemade to give a short sketch of the particular conditions to whicheach is most Cross-section of a Creek Bed. To do this let us consider the above cross-section of a creekbed. First we have a muck composed of frozen organic mattercontaining about 75 per cent, ice and varying from 2 to 30 feetin depth. In almost all cases this is quite solidly frozen. Belowthis we have a layer of frozen gravel or silt, varying from 2 to 15feet and carrying a few colours. Underlying all this we havefrom 2 to 4 feet of bed-rock pay, which is composed of the heav-iest wash in the creek beds and contains the best pay. Fromthe above section it is quite plain that before we can get any ideaat all as to. what we have we must get down through from 6 to50 feet of waste material. The methods of attack here woulddepend simply on the depth. For all prospects where bedrockis not over 15 feet open cutting and ground sluicing would beused; when more than 15 feet deep shaft sinking and driftingwould be resorted to—the Keystone drill could be used here also. The dangers met with i
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