In the US the land owner may not own(or in possession of) the mineral rights. I hold a great deal of rights in AZ,NV and Utah and even a few in TX. This nugget was found in Australia - not sure about there but I suspect it is the same.
When I was looking for property in NV I wanted to get rights but the seller of the section I settled on elected to retain them and halve the price. I figured it was OK, I could always buy or lease them back if I found something and I’ve got 2560 acres of BLM immediately adjacent I can stake if I found stuff trending there or off it.
You can own all mineral rights (includes water and timber) if it is an old, legally purchased, patented mining claim, as my property is.
No idea what you are talking about. I own the mineral rights to MANY pieces of family property all over Texas, and my family has collected money from them for several generations.
No idea what the law is like in Australia, but it would seem strange if someone where allowed to come onto your land and pick up anything they wished and claim it whether you had the mineral rights or not.