The area I live in is very low in minerals. I bought the 10.5DD HF to hunt the beach but with my bad shoulder, I just haven't used it very much and am thinking about selling it. I have compared it to the stock 9" concentric and the difference is just about "0", they are real close to the same except for the weight factor, the 9" is so much lighter. I have also compared my 6"DD HF to the stock coil and the stock coil is maybe 1" deeper but the 6" is a dream in trashy areas and I can swing it all day with my bad shoulder. I have honestly found silver dimes with my 6" at a measured 8", not bad for such a small coil, it is definately a keeper....The 10.5"DD would excel in highly mineralized soils, I will be putting mine up for sale soon. HH John