Mining technology - statistics 1972 and 1973 developments / Amil Dubnie, Mining Research Centre. : M34-20/188E-PDF

“The tonnage of metallic ore mined underground in Canada decreased in 1972 while a corresponding increase took place in the tonnage mined from surface bringing the latter to 72% of the total. In the non-metallic less coal mine category, tonnages showed only a minor increase. In coal mines, the tonnage derived from surface increased, reaching 79% of the total for the group. During 1972, about 37% of underground metallic ore was mined by the cut-and-fill method or variations, followed by open stoping at 31%. The general trend of underground mining costs is up, while productivity has not shown a comparable rise. Costs and productivity in surface mines are holding approximately at previous levels. Promising advances in underground mining during 1973 were the use of a "roadheader" for mining without drilling and blasting under certain conditions, and the application of large-diameter holes to open stoping"--Summary, p. i.

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