A drywasher is a common desert mining tool for gold mining. It is much like a highbanker, since it uses a motor and a form of sluice, but it has no need for water.
The drywasher operates by the use of air. By forcing air to flow up through the material as it moves down the sluice, the heavier materials, like gold, will stay at the bottom and get trapped by the riffles while the lighter materials will flow up and over the riffles or be blown away. The lighter material that is not blown away will slowly flow down the sluice and fall out the end of the sluice.
Ironstone's Heritage Museum is home to a very old and rustic drywasher. This unit made of wood and canvas hales from the early 1900's. Our guess here is the air was passed through via bellows and a strong arm.
Modern drywashers, hooked up to pumps are made of stainless steel and require minimal effort on the prospectors part.