Mineralized soil contains high amounts of magnetite and/or other iron oxides. Basically the black stuff you see that attaches itself to a magnet when you drag it through dirt.
High levels of mineralization affect ground phase readings and also attenuate (weaken) the magnetic field that is put into the ground by the coil and because of that, limits detection depth.
High ground phase readings can be indicative of mineralization but other things in the soil can affect the ground phase besides mineralization so ground phase cannot really tell you that the soil is mineralized.
The only way to tell the level of soil mineralization is to use a mineralization meter. Many First Texas detectors, the XP Deus, and even the Nokta Simplex+ have mineralization level meters. High or variable levels of mineralization can cause large swings in ground phase which can be mitigated by using a detector with tracking ground balance to detect changes in mineralization and rebalance automatically on the fly.
The Equinox senses mineralization changes and rebalances in tracking mode, but does not explicitly display mineralization level. The Equinox measured ground phase number can vary depenending on selected mode for a given spot and that is why you need to ground balance separately for each mode and is also the reason the Equinox displayed ground phase number tells you absolutely nothing about the level of mineralization at your site. In other words, a high ground phase reading on the Nox does not necessarily mean the ground is highly mineralized.
To mitigate the effects of mineralization on detection depth loss and excessive ground noise with vlf machines - use tracking GB or rebalance frequently, try to use smaller coils that don't see as much ground, minimize the output power of the transmit coil, if possible, and use lower frequencies that are attenuated less by the ground. If possible, use a PI detector which is generally unaffected by mineralization due to the different principle it uses to detect metallic targets.
HTH
