Here is a photo with some gold nuggets from Alaska, Australia, and California that I tested recently to show how VDI (visual display indicator) numbers vary dramatically with size, shape, and purity. Metal detectors do not know what metal is being detected. The target id number is based first on the conductivity of the item and also by the size of the item. Low conductive targets have low numbers, but the larger they are the higher the numbers go. Silver is the best conductor with gold bein