Really? how do you do that? You leave it there for some time then you was it?
That's my same opinion on the subject 
I have the stub end of a 30mm shell fired from an A10's autocannon. I feel the same way.
(Note: I sealed it in plastic)
I also have (the very likely asbestos-impregnated ) fragments of concrete from the Apollo 1 and Mercury launch pads at NASA.
