Surely all energy is interchangeable. Rub two sticks together conferring kinetic energy and you can start a fire giving off heat energy to put it crudely.
There's no 'surely' about it. Obviously everyone can do it their own way, I was just describing my 'in game' explanation of why you might not be able to use Lord Research as a Mentalism user. No, you don't HAVE to give a reason, but a GM that
routinely does not have logical explanations will likely find themselves out of a group. If you can't come up with a reason other than balance (which is a fine reason) then no biggie, but if you
can come up with a reason, so much the better.
Again,
I treat Mentalism essentially as Psionics. You cast using your
own mental energy to fuel your 'magic'. So, what you describe is not mental energy.
My explanations...
Essence you are using elemental force/energy to create an effect.
Channeling you are using other living beings force/energy to create an effect.
Mentalism you are using your
own mental force/energy to create an effect. Your own mental energy does not come from a rock (unless you're Biff from Back to the Future).