A mineralization meter tells you how much magnetite or other similar ferrous oxide compounds are in the soil.  The ground balance indication on most detectors is really just a number generated to help a user properly balance out ground phase (conductivity).  It does not necessarily correlate to the degree of ferrous mineralization present in the soil.  Even if you have a properly ground balanced detector, highly mineralized soil (often referred to as "hot ground") reflects and attenuates the mag