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How did petrological analysis show that Stonehenge stones came from Wales?

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Archaeology Archaeologists mapping their finds at Pachacamac, Peru, an Indigenous town occupied from approximately 200 bce to 1532 ce, when it was sacked by conquistadors under the command of Francisco Pizarro.

In the early 1920s, H.H. Thomas of the Geological Survey of Great Britain utilized petrology—the scientific analysis of rocks—to determine the geological origins of the stones used at Stonehenge.1

By conducting a detailed petrological examination of the monument's bluestones, Thomas was able to match their specific mineral composition and characteristics to the unique rock formations found in the Preseli Mountains of north Pembrokeshire, Wales. This analysis provided definitive evidence that these massive stones were not local to the Salisbury Plain but had been transported approximately 200 miles from their source in west Wales to the construction site over 4,000 years ago.21

This application of petrology remains a fundamental technique in archaeology, allowing researchers to identify the origins of lithic artifacts, map prehistoric trade routes, and understand the logistical capabilities of ancient societies.1