A small nugget with the GPX 6000, I thought the signal given was very weak for the size of the gold. 

Yes it is very odd, I cannot figure it out? A Minelab dealer in Oregon, USA explained this to me:: The Coiltek 10x5 Goldhawk was our most sensitive 6000 coil available and is also runs quiet with sensitivity at 3 or less. The 10x5 Goldhawk was about 1” inch deeper than the 12x7 Xceed on a 3 grain nugget.

This is the Algoforce on the same nugget, I think it does a much better job on this particular nugget than the GPX 6000 even though the Algoforce is running a bigger 10" coil. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-KcHr68OEJFA.html