The results revealed that the Altar Stone has a distinct composition compared to the other bluestones, including a much higher concentration of the element barium. The team said the discovery suggests that “it is time to broaden our horizons, both geographically and stratigraphically into northern Britain and also to consider continental sandstones of a younger age,” according to the study. “Thomas grouped the Altar Stone with the other foreign stones, calling them the 'Blue Stones,’” Bevins told Motherboard. “But the Altar Stone is anomalous in its size, weight, and rock type, and there is no evidence for when the Altar Stone might have arrived at Stonehenge” whereas “the bluestones are thought to have arrived ca 2950 BC during the Stage 1 construction period.”