Crushing Gold Ore

Crushing Gold Ore. . An arrastra is a type of primitive mill used to crush ore and extract gold and silver. Water diverted from Willow Creek turned the large water wheel to provide power. A drive shaft connected to the wheel rotated a series of cogwheels that in turn dragged stones around the basin, crushing the ore.

Miners hauled ore to this arrastra, where it was placed into the basin to be crushed. Once the order was broken up into smaller pieces, the operator would pour mercury into the basin, continue grinding, rinse out the rock fines, add more ore, and repeat the process. After the ore had been pulverized, the amalgam-gold captured within the mercury was carefully recovered from the low places and crevices on the a arrastra floor. The amalgam was then heated and distilled to recover the gold, and the mercury was saved for reuse.

Spanish Origin , Arrastras were widely used throughout the Mediterranean region since Phoenician times. The Spanish introduced this technique to the New World in the 1500s. The term “arrastra” comes from the Spanish word arrastre, meaning to drag along the ground. Because arrastras could be built from local materials and required little investment capital, they were suitable for use in remote areas, such as South Pass City.

Picture caption: This arrastra, located near Baker City, Oregon, is similar to the Flood and Hindle Arrastra that operated here along Willow Creek. Circa 1890.