Two alluvial deposits can look similar in a photograph and require very different washing circuits. The important question is not whether clay exists, but how the material behaves when wetted and agitated.
Free-washing feed
Free-washing gravel breaks down rapidly with water and moderate agitation. The process can focus on stable feeding, oversize removal, classification and gravity recovery.
Even here, excessive water is not automatically helpful. High dilution increases pumping and settling duties and can reduce control in downstream separators.
Plastic or sticky clay
Sticky clay may roll into balls, trap dense particles and pass through a screen without releasing its internal sand. This material needs residence time and attrition. A short trommel fitted only with spray bars may wet the surface without completing disaggregation.
The washing stage should be evaluated by the condition of its discharge, not by how forcefully water is sprayed into the feed.
Slime generation changes the downstream problem
Aggressive attrition can release valuable fine particles, but it also creates a larger ultrafine stream. That stream may increase slurry viscosity, overwhelm settling capacity and carry fine gold into tailings.
The flowsheet therefore has to balance liberation and slime control. The correct answer can include separate treatment or rejection of a fine fraction, depending on its gold content.
Test with representative material
A useful test records disaggregation time, water demand, screen behavior and gold distribution by size. A jar or bucket observation is a start, but bulk variability should be considered before sizing the plant.