long Tom
A device formerly used in California for washing gold from the earth or mineral spoil with which it is excavated. It is a sloping wooden trough which widens at the lower end.
Long Tom: gravity sluice for alluvial gold recovery
A Long Tom is a wooden trough, typically 10 to 12 feet long and 18 to 24 inches wide, used to separate placer gold from gravelly soil and sediment. Water and material flow downslope through the trough; gold, being denser, settles in riffles or ridges on the floor while lighter material washes over the end. The trough widens toward its lower end, sometimes flaring into a section 3 to 4 feet across, which improves settling and reduces turbulence.
The device gained prominence during the California Gold Rush as a step up from simple panning. It processes far more material per day than hand methods, yet requires less infrastructure than a full stamping mill. A crew operating a Long Tom could work broken ground, stream deposits, and tailings from earlier operations. Water supply was critical; the trough needed steady flow, typically diverted from a nearby creek via wooden flumes or channels.
Construction and operation
Miners built Long Toms from local timber, usually pine or oak planks nailed or bolted to a wooden frame. Riffles were cross-pieces of wood, stone, or iron fastened to the trough floor in staggered rows, spaced a few inches apart. Finer material, clay, sand, and powder-fine gold, often needed additional recovery; operators would periodically stop flow and pan the settled material from the trough bottom, or use a cradle or rocker on the discharge to catch finer particles.
The name "Long Tom" appears in mining literature of the 1850s, though its origin is unclear; some sources attribute it to a generic large gun of the era, others to an early operator or supplier. Regional variants existed: the Hungarian trough and the shaking sluice used similar gravity-sorting principles but with different geometries or motion. As hydraulic mining expanded and powered equipment became available, Long Toms fell out of use, though small-scale and recreational miners still employ the principle today.
Wear was steady and predictable: wood rotted, especially in the riffles where moisture and fine sediment accumulated. Panning the trough bottom and cleaning riffles were weekly tasks on active claims. The device's greatest limitation was its inability to recover very fine gold efficiently; anything smaller than flour-fine tended to wash away.