Launder: From Clothes to Ore Troughs

To most people, laundering means washing clothes, linen or other textiles to remove dirt and stains. The word came into English from Old French lavandier, the person who did such washing, and ultimately from Latin lavare, to wash. That everyday sense still dominates.

In mining, a launder is something altogether different: a long, shallow trough, typically made of wood or later cast iron, that channels material through the ore-processing circuit. Crushed ore from the stamp mill falls into the launder and flows along its length, often assisted by running water. The current carries fine particles toward the next stage of separation, whether a buddle, a pan, or a classifier. The launder might also supply water directly to the stamps or other comminuting equipment.

The connection between the two senses is literal flow. Cloth laundering relies on water flowing through fabric to carry away dirt. Ore laundering relies on water and gravity flowing through a trough to carry crushed rock toward recovery of valuable minerals. Both harness the transport power of moving water, which is why miners adopted the familiar laundry term for their own apparatus.

The trough itself had to meet exacting specifications. A launder had to maintain even gradient to prevent settling or overflow, withstand abrasive stone and continuous water action, and discharge material at the right velocity and volume to feed the next machine. Worn or damaged launders were replaced regularly, making them consumable items in any hard-rock mining operation.