Mining Methods and Costs at the Spring Hill Mine, Montana Mines Corporation, Helena, Mont |
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adit April 30 Bench Old Stope Blockholing bonus system bowlders Bureau of Mines cent strength gelatin chute door Cross section crosscuts day shift difficult to bar Diorite 100 diorite side Drift Drift 300 drill steel Drilling and blasting drills 1-inch hollow Ducktown Figure 1 Diorite foreman gage Grab samples grizzly chamber Grizzly Slabbing Bench hard and tough haulage level Helena holes are drilled intermediate level investment in broken irregular jackhammer Labor man-hours Leyner-type machine Limestone Grizzly Slabbing man-hours per foot marbleized miners MINING METHODS Montana Mines Corporation nearly vertical night shift Numbered old opencut old pull holes percentage of total Power and supplies pyrrhotite round seams section at A-A shaft Shoveling Shrinkage stoping Slabbing Bench Old Spring Hill stoper drills strength gelatin dynamite Stull sublevel stoping Tennessee Copper Co Timber board feet Timbered grizzly timbered raises Tons ore trammed total cost track underground ކ ކ ކ ކ ކކ ކކ ކ ކކކ