After more than 60 years, a piece of Stonehenge was replaced by archeologists in 1958 from one of the gigantic stone columns.
No one knew where the one-meter-long piece was drilled from within one stone, while one of the participants in the excavation, 90-year-old Robert Phillips, did not decide to return it, wrote the BBC news portal.
The English Heritage office, responsible for the vast prehistoric stone structure, hopes that the sample will help determine where the stones came from.
In 1958, archaeologists worked to prevent the collapse of a three-stone structure: two columns held a third, lying horizontally on them.
One of the vertical stone blocks found cracks. They decided to reinforce, so they were drilled in several places and fitted with metal bars in the hollows. Traces of repairs were disguised with sandstone pieces found during excavation.
Robert Phillips took one of the drilling pieces of stone with him. At first he held his workplace in a plastic tube, and after he retired and moved to Florida, he placed it on the wall of his American home.
To strengthen the gigantic stone blocks, a diamond-cutting company was asked for help, the man at that time working with them, so he got to the archaeological excavation. The staff at Van Moppes raised three pieces of one-meter stone from inside the array, and Phillips took one of them.
But on the eve of his 90th birthday, he decided to return the stone.
Archaeologists hope that analyzing the pattern can help determine where the stones of the building came from.
Though the stone was returned by the man last May, the Heritage Office only reported it because they wanted to make sure the sample was genuine.
It remains a mystery where the other two patterns can be.