Metal detecting is illegal in the Pine Barrens, at least it was when I looked into it. Also, don't go there in late summer, where the bugs will eat you alive. I don't know what it is, a chigger, a no-see-um, whatever it is. you won't know it is biting you and laying eggs in you until the next day, and it is brutal.
For those interested in exploring the Pine Barrens, and it is a cool thing to do, pick up "Forgotten Towns of New Jersey" and "More Forgotten Towns of New Jersey" by Father Beck. Also, the local historical societies will have really cool old maps that you can't find online.