The team studied the age and chemistry of mineral grains extracted from the rock fragments. The analysis is consistent with rocks from northeastern Scotland, while at the same time there are clear differences from the Welsh bedrock. The analysis found that the specific mineral grains in the altar stone are mainly between 1,000 and 2,000 million years old, while the other minerals are around 450 million years old. This gives different chemical signatures, indicating that the stone came from rocks in the Orcadian Basin in Scotland, at least 750 kilometres from Stonehenge.
Previous analysis of the site identified two main types of stone used in construction: sandstone from nearby Marlborough (about 25 kilometres away) and basalt from Wales.
The Altar Stone is a 50cm thick block of sandstone at the centre of the Stonehenge circle. The stone, along with the rest of the structure, is thought to have been moved to its present site in Salisbury around 500 years ago.
Transporting the stone from Scotland must have been much more difficult than transporting it from Wales, suggesting that advanced means of transportation and social organisation were in place by the time the stone arrived in England.
At the time of transportation, transportation in Britain was much more difficult than it is today due to the geographical characteristics and forested nature of Britannia.
Image: JimPix/BBC Science Focus
Transporting such a large load from Scotland to southern England by land would have been extremely difficult, so it was probably a sea voyage along the coast of Britain. This suggests a far-reaching trade network and a higher level of social organisation than is widely known in Neolithic Britain.
It is not yet known exactly where the altar stone in north-eastern Scotland comes from.
It is not known for certain why Stonehenge was built, as those who built it left no notes or writings. Stonehenge is a sacred site that has been continually added to and rearranged over 5,000 years. The first structure in 2900 BC was a circular ditch with a large wooden inner ring of pillars.
(Source: BBC Science Focus: https://www.sciencefocus.com/)
