This is such an odd metaphor. The madness is now shining out of Hamlet like gold in a pile of junk metal? Extended, it would seem to imply that Hamlet is the junk metal and the madness is the gold? I think the junk is REALLY meant to be all the rumors flying around his madness – but it’s a little bit clunky. The oddness of this metaphor seems to me to reflect how confused Gertrude is at this point