Taking a chip off the old Rock has apparently become a dangerous pastime for tourists visiting Australia's Red Centre.

Every few weeks, parcels and envelopes containing rock mementoes illegally removed from the sacred Uluru-Katatjuta National Park are returned because they have reportedly brought bad luck.

Administrators at the park, visited by thousands each year, have dubbed the returned mementoes "conscience rocks".

Dr David Carter, of the Australian National Parks and Wildlife Service, says most mail is accompanied by tales of woe.

"Perhaps the saddest of all came from an Australian who wrote that since he'd collected the rocks on a tour, his son had broken his leg, his daughter had been picked up for under-age drinking and his marriage had broken up," he said.

"He had been picked up for drink-driving and, along with a series of other minor misfortunes, considered he'd had enough bad luck for one lifetime."

The man blamed the rocks and asked park officers to return them to Uluru (Ayers Rock) from where they had been taken.

While most packages contained a few small rocks or sand, Dr Carter said one contained a rock weighing between 10kg and 15kg. "It must have cost a fortune in postage," he said.

"Some of them come anonymously, others have notes with them apologising for taking them."

…But he did not think there was anything to the bad luck notion. "I think people are just looking for something to blame," he said.