You have asked a very good question and the situation you describe is not uncommon in certain areas in the U.S. Also, it is not unique only to the X5. Through the years, I have experienced what you described with many detectors, both manual and auto tracking ground balance detectors. In fact, the soil in my yard creates the same situation. It has almost zero mineralization but this type soil (black gumbo as we call it) does have what is called a high loss angle to metal detectors. Which means it has properties with high electrical conductivity. Anyway, from a practical standpoint I have often found almost the same results you describe.

Now, when a person starts adjusting the ground balance under these conditions, he can get into trouble as it is almost the same as trying to ground balance in the air. Since, detectors will not ground balance to air or in the conditions you described, just where should the ground balance control be set? Well, if your detector will not ground balance at these locations and there is no reference point to set the ground balance control, then the GB will most likely be set "in the blind". This is a bad situation and can actually impair the performance of your detector without you even knowing it. If it is blindly set too positive then what happens? Loss of depth, especially on high conductive targets. You can actually tune out silver dollars with the ground balance control with some detectors. What if it is set too negative? Overall loss of depth and excessive ground noise.
Since I experience these situations often in my immediate area, I have studied this for many years and have come to the following conclusions. 1) Under these situations there is very little or no iron mineralization. 2) Under these conditions the detector does not radically lose depth because the detector sees very little iron mineralization. 3) Can you hurt yourself by blindly adjusting the Manual Ground Balance control? You bet you can and you will!!!

Now, you probably already know where I am going with this. hahaha! My solution to this problem appears on the X5. It's called Fixed Ground Balance! You see, fixed or preset ground balance is set for the maximum performance from your detector. I look it like this, when manual ground balance is used in iron mineralized soil, to some degree, you are actually trying to over compensate what the detector normally sees as a target. This can actually be viewed as mis-tuning the detector from its optimum state to try to improve bad conditions. The analogy you have heard many times is true. Ground Balancing in heavy iron mineralized soil is very similar to driving an auto at night in heavy fog. To improve a bad situation it is best to use your low beam headlights instead of the high beams. High beams are preset for maximum performance just as fixed or preset ground balance is set for maximum or optimum performance for your detector.

There are two very good reasons to have both Fixed and Manual Ground Balance on the X5. First, some people just prefer to use Fixed GB as their hunting conditions do not require the benefits MGB can provide, but the main reason is for my own use! I don't like to guess where I should set the MGB control when I can not adjust it correctly. The Ground Balance adjustment is simply too critical. So my advise is, to always use Fixed Ground Balance when you find yourself in a situation that does not allow Manual Ground Balance to be adjusted correctly.

Now here is a tip that is unique to ground balancing the X5. It operates at 19khz and is much more sensitive to small and low conductive items as opposed to most other detectors when hunting in the Discrimination Mode. With the power of the X5 (depth and footprint) it is seeing much more ground area than normal. When this type of power is combined with 19khz type of sensitivity, it is best to adjust your Ground Balance control slightly more positive than normal to tune-out or reduce low conductive ground noise. This is very important and you find with a little experimenting, your X5 will operate much smoother and still maintain superior depth.

Troy