The pit was created bit by bit over almost 60 years through three mining phases: the Sacramento Pit, mined from 1917 to 1929; the Lavender Pit, mined from the 1950s to the 1970s; and the Holbrook Extension, mined from the late 1960s to the 1970s. Open-pit mining here used a series of fifty-foot-high benches, or steps, cut into the edge of the ore deposit. Closely spaced holes were drilled into the benches and filled with explosives, the explosives were detonated to break up a layer of rock, and the broken rock was shoveled up and hauled away. The older Sacramento Pit used steam shovels and ore cars on railway tracks, while the newer Lavender Pit used electric shovels and haul trucks. Ore went to the crusher for further processing, while waste rock containing little or no copper was hauled away. Over the years, open-pit mining required larger and larger shovels and haul trucks so operators could move greater quantities of rock, cut costs, and use fewer workers. In 1954, haul trucks at the Lavender Pit held 35 tons of rock; by 1974, they held 65 tons; and today, typical haul trucks in Arizona copper mining carry 260 tons or more. Whether rock became ore or waste rock depended on economics: if extracting the metal cost too much it was called waste rock, but if metal prices rose or cheaper extraction methods were invented, that same material could become ore. Spiral roads connecting the mining benches carried trucks hauling copper ore or waste material; waste went to the No. 7 Stockpile, and ore went to the crusher and then by conveyor belt to the concentrating mill across the highway. After the mine closed, these processing facilities were removed and remediated.