Among the many megaliths of Stonehenge, one large slab stands out in the eyes of scientists.
The Altar Stone, also known as the number 80 stone, is a ‘leaning’ stone slab in the inner circle of the famous Neolithic monument, which is said to have once been 4.9 meters high.
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The origin of Stonehenge continues to be a mystery
Right now, the purple-green sandstone lies embedded in the ground, smothered by two blue igneous rocks.
The appearance of Stonehenge in southern England is considered to be one of mankind’s greatest mysteries. For nearly a century, the origin of the 80 stone was linked to the others.
A new geochemistry and mineralogy study of the Old Red Sandstone Foundation in West Wales reveals something interesting, however.
“One of the key features of the Altar Stone is its unusually high barium content,” explains the international team of researchers responsible for this study.
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The presence of barium in the composition of the Altar Stone, an important detail
Of all 58 samples taken from the Old Red Sandstone, from West Wales, however, only four had barium levels close to the lower range of the Altarstone composition.
Despite their higher barium levels, the mineralogy of the four stones from this Welsh region did not match the fine grain of the Altarstone.
Much of the sediment in West Wales comes from Devonian rock which is about 400 million years old.
Admittedly, it matches the blue stones of Stonehenge quite well, but this substrate does not have enough barium to explain the composition of the Altar Stone.
As a result, scientists suggest that the origin would be related to the Permian or Triassic period, that is, dating from 200-300 million years ago.
For example, barium is known to be abundant in Northern Ireland, as well as north-east Wales and parts of north-west England.
Several of these regions also host sandstone Neolithic monuments, the authors of the study note.
Even the cliffs as far north as Scotland are worth investigating, as the sandstone formations in this region are barium-rich and non-marine in origin. Additionally, both match the Altar Stone.
“This Welsh source for the Shrine Stone has gone unchallenged for nearly a century,” the scientists also said.
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