That's what I was wanting to know. Your red dirt in VA does have the weird bedrocks in it...I remember with the F75 that it would give a negative GB noise over every big rock in the fields in Culpeper. Most of the red dirt here don't have that...instead it is a lot of blackish iron ore rocks in it and white quartz. There are a few hot spots around that have the same bedrock outcroppings as the VA rocks in Culpeper....in which I can't even balance a VLF machine in. The only thing that balances in it are the pulse machines.
The rest of our red dirt is the milder form but that's not saying much because I have a silver US quarter buried at 8 inches exactly in my clean yard and of the VLFs I currently have....none of them pick it up at all...not even in all metal or open quickmask (Coinstrike, Omega, and eTrac). But 4-5 inches in the same dirt and I can get a silver dime and minie ball...they just read as iron.