Sometimes, it is too late to say you’re sorry.

Petrified Forest National Park, which was designated as a national park on this day in 1962, is astounding. Its beauty has prompted thousands of visitors to the park to, well, pick up some of the rainbow-hued fossils that are all that remains of a prehistoric forest. And, well, take them.

In recent years, the staggering figure that a ton of glittering petrified wood was stolen the park every month from has been shown to be a myth, writes Brian Switek for Smithsonian Magazine. Park superintendent Brad Traver and park paleontologist William Parker debunked that one. But people have still stolen from the park, and the wood once removed can’t be put back.

Hence what park employees call the “conscience pile,” writes Nicola Twilley for The New Yorker:

About the size of a pickup truck, it is a jumble of chunks of petrified wood, the fossils of trees that fell more than two hundred million years ago, the cells of their bark and wood slowly replaced with minerals of every colour--purple amethyst, yellow citrine, smoky quartz. These are all the rocks that have been stolen and subsequently returned by light-fingered visitors who came to regret their crime.

Many of those delinquent visitors accompany their returned rocks with a letter. Some are poignant, and many are from kids, writes Conor Knighton for CBS News. “To park ranger, I am so, so sorry for taeking [sic] the petrified wood. I didn’t know it was so speshall [sic],” he quotes one as reading.

Some others are from people afraid of an alleged curse carried by the wood. The park used to make a big deal of the curse, Knighton writes, displaying letters about the wood’s return in the visitor centre. Perversely, the display prompted more letters, and presumably more theft. In fact, a 2006 study found that messages in the park stating how much wood was taken led people to take more wood by normalizing the behaviour.

Today, the park’s messaging focuses on how beautiful and accessible the park is. “By trusting visitors and showing them how to best enjoy the prehistoric beauty, Petrified Forest has given people a new reason to care about this slice of prehistory in the Arizona desert,” Switek writes.

Sadly, though, the conscience pile can’t be undone, and even the letters that contain detailed maps of where a particular rock was taken from don’t enable park stewards to return it, Twilley writes. Doing so would spoil that piece of the park for research purposes, artist Ryan Thompson writes in the introduction to Bad Luck, Hot Rocks, his book about the phenomena.

The good news is, most visitors don't take things and the park is mostly intact. "People get the same experience as if they came here in 1880," Parker told Switek.