The woman stole a bag full of the unusually coloured grains during a holiday to Sardinia, from where you can take boat trips to Budelli's Pink Beach, in 1987, according to Il Resto del Carlino.

Now she has sent the sand back to its rightful place, along with a note explaining and apologizing for her actions.

Naming herself only as Antonella, she explained that shortly after her return home, she discovered how important the sand was.

“I read in some newspapers and heard on the TV what this sand is and how it is made, how it is a natural park,” the letter read. “I understood how unique Sardinia is. So I felt guilty and kept it hidden, always with the idea of returning it to the island.”

But the turning point which gave her the final push to send back the sand was the news last week of an initiative by a group of Piedmont schoolchildren, who have begun fundraising to buy the beach.

The children, from a middle school in in the Alpine province of Biella, say that if every Italian child pitches in €0.50 then they could club together to buy the island, which they would name ‘isola dei ragazzi’ (the children’s island).

They told La Stampa: “The message we want to convey is this: if all Italian school pupils donate €0.50 each we could raise the €3 million needed to win the next auction, which means this piece of heritage won’t fall into the hands of a stranger.”

The island has been at the centre of a legal battle for several years, after it was bought at auction by a New Zealand banker in 2013. He recently pulled out of the deal, despite winning an appeal after the government passed a law allowing the state to buy back the island.

Giuseppe Bonanno, president of the national park, is grateful for the sand's return.

“We thank Antonella for the choice she made in giving back this little bit of the Pink Beach to its natural habitat. It’s never too late to realize the importance of your own gestures for the maintenance of natural balance in an area. We also thank the children of Mosso because with their activism they raised awareness of looking after a natural beauty like the island of Budelli.”