Fluid Bed Sluices

How Well Do They Work?

- Marc Davis

An old friend with a new twist” might be one way to describe a fluid bed sluice box. I’ve been mining with sluice boxes since the 1980s, so to me a sluice box is definitely an old friend. The new twist is that fluid bed sluices do not use a set of riffles and matting to capture gold like a typical sluice. Instead, they use a fluid bed of sand and small pebbles in a collection box that is cast into the sluice to trap gold.

Prospectors who are familiar with typical sluice boxes know the commonly available version is a long metal trough with a set of angled riffles coupled with some sort of carpet or matting to catch gold. The sluice is placed in a moving stream of water and pay dirt is put into the upstream end of the sluice. The moving water washes the dirt through and out of the sluice, while the gold, which is much heavier than the rest of the material, is caught behind the riffles or in the matting.

In years past, all sorts of devices besides metal riffles have been used in sluices as gold traps: stones, wooden blocks, steel rails, and just about anything else that miners thought would capture gold. Recently, plastic sluices with molded riffles and no matting have become common (see “Sluice Box Shootout”, July 2012). Now, with the development of the fluid bed sluice, a bed of churning sand and pebbles has joined the ranks of sluice box gold traps.