Ridge Runner,
I have personally found some porous type nuggets that the ZED will see at 6 inches in air testing, but the best I could get with a GPX was 2 inches ! That is 3 times the depth, much more than Minelab have ever claimed.
Another porous nugget the ZED could air test at 2 inches, and the GPX even with a Sadie coil had to be rubbed on the nugget to get even a murmur, no matter what settings I used !
I have at least 500 hours under my belt with the ZED in real goldfield conditions, and can tell you that the machine rocks on numerous types of gold. The only gold that I have found it to have
little advantage on is solid blob type nuggets.
Anything with a bit of ironstone / quartz through it, or porous or crystalline, or nuggets standing on edge, the ZED will smash the GPX.
Rick