In the defunct silver mines of California, Nevada, and Arizona, Michael Allen Harris spends his weekends unearthing denim left behind by miners dating back to the 1800s. A commercial painter during the rest of the week, Harris is responsible for finding one of the oldest jean jackets ever made. That jacket, along with several of his other best finds, now lives permanently in the official Levi's archives, where the pieces are admired by the company's designers and studied for their hard-earned wear patterns—whiskering, fraying, rips, and tears. As it turns out, crusty old denim, even scraps of it, can be incredibly valuable.

In an interview for theguardian.com, Harris describes how he began mining for century-old blue jeans, as well as the rare thrill of finding an entire intact pair of jeans in the dirt.

“A few years ago, my father-in-law dug up the holy grail: the oldest pair of Levi’s from 1873, the first year they were manufactured. I wish we could keep them for our personal archives, but recently I had an offer of about $100,000. My father-in-law doesn’t want to sell them and neither do I, but I have two daughters to put through college, so they might have to go.”

If you live near a place where over a hundred years ago cowboys, ranchers, or miners worked hard in jeans, you might want to start digging.