At an age when most schoolkids are still learning to tie their shoelaces, Nathaniel Prebalick — AKA Gold Plate Nate — was teaching budding treasure hunters how to pan for gold. As a third-generation prospector, he was raised amid the sparkling streams of California’s Gold Country, in the foothills of the Sierra Nevada, getting to know its watery veins as well as the life lines of his own hands.  While this may sound like a sepia-tinged snapshot from another century, it’s anything but — as I discover when I meet Nate on a grassy riverbank one spring morning. He’s a thoroughly modern gold digger — a smiling twentysomething who uploads his gilded finds to Instagram — and he has a ready explanation for why Tuolumne County in eastern California is, once again, in the grip of a gold rush.