Fires a high voltage pulse of signal into the ground. In absence of metal the pulse decays at a uniform rate. In presence of metal a small current will flow into the metal and the time to drop to zero increases.
Silver and gold are both non ferrous metals. Other non ferrous metals are aluminum, copper, platinum, brass, lead, nickel, tin, titanium, zinc, and a list of rare metals
Many Metal Detectors will have difficulties with the following environments:
highly mineralized salt water
Coral rocks with a high iron content,
magnetic (black) sand
Magnetic black sands are heavy, just like Gold. Therefore they will tend to be concentrated with gold at the bottom of a slice.
Gold will usually be carried in hydrothermal fluids and then deposit where it encounters a reducing environment, such as pyrate. It will tend to associate with other dense materials.
Therefore for the choice of your detector we suggest you discuss with a member of our Mining Team.