The Stonehenge is one of the most impressive and mysterious constructions left behind by our ancestors. Now, scientists have found the exact source of Stonehenge’s smaller bluestones: over 200 km away from Stonehenge.

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The stones’ composition revealed that they came from a relatively nearby outcrop about 1.8 miles (3 kilometers) away from the site originally. This site was the proposed origin more than a century ago, but only now did researchers finally determine, with certainty, that this is the source.

The work “locates the exact sources of the stones, which highlight areas where archaeologists can search for evidence of the human working of the stones,” said geologist and study co-author Richard Bevins of the National Museum of Wales.

The discovery of the rock’s origin might play a key part in allowing archaeologists finally understand where all the rocks came from, and how they were carried and set into this position.

The Wiltshire site in England still harbors evidence of ancient occupation, with traces of pine posts raised about 10,500 years ago. The first megaliths at Stonehenge were erected 5,000 years ago, with following cultures adding more and more to the monument.

Most of the creation consists of massive, 30-ton sarsen stones, as well as smaller bluestones, so named for their hue when wet or cut – whose origin was now identified. The so-called blue rocks are actually dolerites. Despite their whiteish appearance, they are subvolcanic rock equivalent to volcanic basalt or plutonic gabbro.

In this new study, the team looked at the minerals, such as chromium, nickel, magnesium oxide and iron oxide, which are part of the crystallizing structures forming in the original magma. They found that at least 55 percent of the dolerite bluestones came from a location, known as Carn Goedog, which is 225 km away from Stonehenge, raising even more questions about how they were transported such a long distance.

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But pinpointing this exact location could provide the needed clues, helping archaeologists to look for more artifacts at the origin of the rock, and perhaps even along the way to Stonehenge.

“For example, if we could determine with confidence that the stones had been worked by humans in Neolithic times, then the ice-transport theory would be refuted,” Bevins said.