Mineral scavengers provide a clue There is another way of detecting the trace elements carried from a deposit by ground water.
Ground water is drawn upward by evaporation at the surface.
During this upward migration, trace elements in the water are affixed to minerals in the overburden. The affixation, or bonding, may range from weak to very strong. The strength of this bonding depends on the chemical nature of both the trace element and the host mineral. The differences in bond strength is comparable to the difference between the weak electrostatic attraction that holds an inflated balloon to a wall and a nail driven into a stud. Trace elements scavenged by these minerals are removed by treating samples of overburden with chemicals that react selectively with each mineral phase.