When little Annabel Utting returned from her fossick around Rottnest Island's Geordie Bay, her parents did not expect to find asbestos among her collected treasures.
"She had no idea," the six-year-old's mother Jacquie said.
"She had these prized possessions she was really pleased to find and we were horrified to see one was what looked like asbestos."
Mrs Utting said her daughter's find on Thursday dampened an enjoyable holiday with her family of five, including Annabel's sisters Emily, 9, and Louisa, 4.
"It's made me really anxious about letting my children frolic around and do what kids do, which is explore and pick up shells and things," she said. "If there's a danger of them picking up asbestos, it ruins the family holiday."
Annabel said she did not know what the light coloured object was but thought she should show her father David, who alerted the Rottnest Island Authority.
"I thought it was a rock and I wasn't sure what it was so I brought it up to my dad," she said.
Regular visitors to Rottnest, the Uttings said the experience had not turned them off their "idyllic" island but they expected the authority to clean the area thoroughly.
Contractors collected the piece, described as 10cm by 5cm wide and took it for testing.
They also made a sweep of surrounding units and found what appeared to be other small pieces.
An RIA spokeswoman said rain or ground disturbance could uncover old material and it had strict guidelines.
Asbestos roofs on the island were replaced in 2005.
"All asbestos roof material has been removed and a risk register documents any known remaining materials," the spokeswoman said.
"Where appropriate, units containing asbestos have a warning notice. Asbestos in a stable condition is not dangerous to health."
An avid explorer and collector, Annabel said she was not deterred from her pastime.
"Hopefully it's not there any more," she said.