You gotta remember, the MXT is good but not very bright.
Think of a chart with three columns. C/J, Relic and Prospecting. Prospecting is different so I'll skip it.
The machine detects a target. It analyzes the target and comes back with a VDI number. Then it checks the mode you are in so it knows which column to look in and picks a word that corresponds to that value.
Check it out. A 20 in C/J will always say, Nickle/Ring. In Relic it will say something else, I cannot remember what. It is as simple as that. It is a word association with a very limited vocabulary based on what White's engineers have programed into it.
Many factors affect the VDI value of a target. It's mass, shape, physical size and, of course, what kind of metal it is.
Think of the common pull tabs. Have you noticed how a particular type of pull tab can register at very different values? Now notice that each one of them is bent or mangled in some specific way making it register different. The angle it is in the ground is also significant.
Now take any and all of the gold rings you have access to. Yours, your wife's, any friends that may be with you. They will probably all register different. Now to compound that even further, throw in some bracelets, earrings, necklaces and any other jewelry you can come up with. Now, just for giggles and grins, take the same stuff and simply change the orientation of each item. I expect you will get different values from the ones you previously got.
Now you can see why it is so hard to find gold. It goes by many names (VDI numbers). It is not any particular detector, MXT included. It is the nature of the beast. If you want to find the good stuff you will have to dig up a lot of trash that will hit at the same values.
Figure it out. There is lots more trash than treasure. That is why you find more trash than treasure. That if why we call it treasure. It is scarce.