You searched for: “illuviations
illuviation (s) (noun), illuviations (pl)
The accumulation in a lower soil layer of materials consisting of soluble or suspended minerals, clays, salts, and colloids (very tiny particles of minerals) that have filtrated down from an upper level: Some gold prospectors were checking out the illuviations in the area to see if there were any deposits of gold in the geologically leached minerals.