Last week, we learned about extracting raw mineral ore. This week, we’ll learn about the process of milling, which is the first of two steps required to take raw mineral ore and turn it into a usable product (the second of which is smelting, which we’ll explore next week!)
This photo features an ore grinding mill from Hercules Mining Company which operated from 1901-1924 in the Coeur d’Alene Mountains in Burke, Idaho. Milling is the process of separating ”metal bearing minerals … from waste material to form a concentrate … This is often done by adding chemicals to the ore materials and running them through a series of processes. The waste from the mill, or ‘tailings,’ is then pumped to a tailings storage facility. Other techniques include gravity separation, where two or more minerals are separated by movement and the force of gravity and one or more other forces.”1 Techniques often differ based on the material.
Stay tuned for next week’s post on smelting as we continue our series on Mining!
Photo courtesy of George W. Tabor Photographs, University of Idaho Library, Special Collections and Archives