Considering some of the (bleep) that's being sold, a cross between lava and mud still having buyers wouldn't surprise me. And I guess it would be the plebs that continue to collect until none are left. But we're taking a comic strip a little too seriously ...
Not to be a scientific-accuracy Nazi, but wouldn't all the mud boil away if it went all the way down to the molten hot earth's core? There has to be something in between...