arrastre

Arrastre is a primitive ore-crushing device used in mining, notably for gold and silver, from the 18th through the 19th centuries in the Americas. The name derives from the Spanish to drag, reflecting how the mechanism operates by dragging heavy elements over ore. It is often described as an early alternative to more complex milling methods and was common in regions with limited capital for steam-powered equipment.

Construction and operation typically involve a shallow circular pit or trough lined with abrasive material or stone. A heavy drag stone or rolling weight is connected to animals, such as mules or oxen, that walk around the circumference of the pit. As the animals move, the drag stone or wheel is pulled over the ore mixed with water, crushing the material beneath and between the bed and the weight. The resulting crushed ore forms a slurry that is then transferred to settling beds, sluices, or other recovery processes. In many cases, the ground ore was subsequently treated with mercury to form an amalgam for gold extraction.

Geographic and historical context: arrastres were widely used in mining districts across the Americas, including parts of Mexico, Peru, Chile, California, and the western United States, before the widespread adoption of stamp mills and more modern processing plants. Their simplicity and low capital requirements made them attractive in frontier and colonial settings, though they were labor-intensive and less efficient.

Legacy: Arrastres illustrate early, low-cost approaches to mineral processing and reflect the transition from manual to mechanized mining technologies. They declined as larger, power-driven mills became available, but remain a significant part of mining history.