Golden, CO (KUSA) - We're learning more about the mine shaft, where a 15-year-old Golden High School student fell on Thursday.

He skipped class and tried to climb down an abandoned clay mine in Jefferson County with a couple of friends. The clothing line he was using snapped and he fell about 60 feet. That prompted a 3-hour rescue, which played out in front of the lens of the news chopper.

The teen broke his leg pretty badly, and he might face charges for entering that closed area in the first place.

Jeff Graves, the Program Director with the Inactive Mine Reclamation Program at the Colorado Division of Reclamation, says that while the whole incident was uncommon, these mines are all around us.

"Most of the sections of hogback along the Front Range, where you have that uplift, have these vertical clay stopes, and clay mines in them," he says.

In fact, someone had to be rescued from an old clay stope south of this hogback near Ken Caryl in July.

"You can actually see the sections of clay that were mined. It's those banded sections along the wall there," he says. "They would have removed that clay and that's why you have these large vertical openings."

In this week's case, Graves says it collapsed relatively recently, and the state didn't even know about it until that teenager's fall. For now, they've put up signs warning people. Down the road they'll likely put a metal grate over the hole, like they have over another shaft that collapsed further down the hogback.

Even though this area is technically closed to the public, people still hike there. You can see evidence of a trail. Graves just wants people to know how dangerous mines are, as tempting as they may look.

"They think they're going to find old relics," he says. "The miners didn't leave gold sitting out. They didn't leave their tools out for people to take home. They cleaned it out. So they're just dangerous openings with lots of potential issues."

The state estimates there are more than 20,000 abandoned mines. They've been able to shore up about 10,000, but they need your eyes. If you see something like that, report it.