Prospecting and Mining of Copper Ore at Santa Rita, New Mexico

Prospecting and Mining of Copper Ore at Santa Rita, New Mexico

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: break down to an even surface. Data regarding several bank and toe holes projected are shown in figure 12. The conditions seemed to be about average for the mine. The results from the blast with these holes were as follows: About 3.2 cubic yards of soil and weathered surface rock was broken per pound SECONDARY OR "DOBE" BLASTING. When the bank holes are exploded, 5 to 15 per cent of the material broken is so coarse (PI. VII, B) that it has to be blasted again in order to be handled easily by the buckets of the steam shovels, which have a capacity of 3 to 3 cubic yards. This secondary blasting is done by placing a number of sticks-of dynamite and a primer, with 42 inches of fuse attached, on the rock to be broken, the size of the charge being regulated by the judgment of the powder man. Formerly it was the general practice everywhere to cover charges of this kind with a stemming of clay or adobe, giving rise to the term "adobe" or "dobe" blasting. This manner of breaking rocks is also referred to as "bulldozing." When the "dobe" charges are all set, the nearest steam whistle toots a warning for the workmen to get out of the way. The chargeman and one or two assistants, each using a piece of fuse equal to the length of the primer fuses (42 inches) as an igniting medium, light the primer fuses and then run to safety. A series of cuts half through the igniter fuse indicate to the men doing the igniting just how fast their fuses are burning and how much time they will have to finish the lighting and get to safety. The number of "' dobe" shots placed is counted, and the number of explosions heard is carefully observed so that any missed or delayed shots will be detected. Prior to the...
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Product details

  • Paperback | 40 pages
  • 189 x 246 x 2mm | 91g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236649737
  • 9781236649737