VLF metal detector discrimination works well on isolated targets in an air test. The problem is in the field what is reported by the detector is the sum of everything the coil "sees". This means the ground mineralization, the gold nugget (or any other item you are trying to find), other metal under the coil at the same time, and even electrical interference. Sweep speed matters also as does the angle of the item in the ground and the direction from which the coil approaches it. Add it all up, an