John McDonald pioneered the use of bulk, low-cost, block caving systems in the underground mines in the United States. From 1903 to 1916, he was the pre-eminent underground mining expert for Daniel Jackling’s Utah Copper Company, and of John McDonald, Jackling said, “No better caving-systems man exists.”
Block caving systems make use of gravity to extract large tonnages of ore from underground mines at very low cost. To initiate a block cave, a thin, horizontal layer of rock is first mined beneath an ore column by conventional drill-and-blast mining. The unsupported ore column then breaks and caves under its own weight into this undercut, where it is extracted from drawpoints.
As the mass of ore caves downward, pressure and attrition reduce it to small chunks. Extraction proceeds without the interruption of drilling and blasting that characterizes other mining methods. Block caving thus permits very large ore tonnages to be extracted on a daily basis and allows extraction of low grade ores that would be uneconomic to mine using other methods.
John McDonald began his long mining career at the age of 12 in the iron mines of Cumberland and Lancashire, England. By 1886, when he emigrated to the United States, he had a quarter-century of mining experience under his belt, and he had become expert in the use of block caving mining methods as applied in the English mines.
When John McDonald first arrived in the United States, he worked in coal mines in Pennsylvania. However, he soon transferred to the underground iron mining district at Ironwood on Michigan’s Upper Peninsula, where he introduced and expanded upon the English block caving systems. He next introduced the system to mines at Iron Belt, Wisconsin.
In 1897, John McDonald moved west as Superintendent of the Delamar and then the Golden Gate gold mines at Mercur, Utah. He introduced block caving into both mines. During McDonald’s time at Mercur, he became acquainted with Daniel Jackling of the Utah Copper Company, and in 1903 Jackling invited him to introduce block caving at the company’s Commercial Mine in Bingham Canyon, Utah. He later became Superintendent.
In 1912, when the Bingham Canyon mines were converted to open pit operations, John McDonald moved onto Ray, Arizona, still working for Utah Copper, and adapted block caving to the Ray Consolidated underground ore body. The following year, he was in the Ely-Ruth district of Nevada, where, as Superintendent, he applied caving methods to the company’s Veteran Mine.
John McDonald was in a class to himself when it came to handling large tonnages of rock below the surface. When he retired in 1916, he had devoted more than half a century to mining underground ores, and he had won the respect of all who were privileged to work with him.