It is a surprise to some that NJ was an old mining state. in fact, mining in New Jersey has been linked by some to the American success in the Revolutionary War. I stumbled into a great website that photographically catalogs old abandoned mines throughout New Jersey.
Just as an example is their page about one of Thomas Edison's copper mines up in Sparta. There is even a book about Edison's mining efforts (PDF). And several years ago we took a field trip (pictured above) through the Highlands where we stopped at several mines including the Hibernia mine, famous for its bats.