Nearly 81 years after the atomic bombing of Hiroshima, material recovered from the city's shoreline is still yielding discoveries that scientists did not expect. Researchers examining tiny fragments preserved in beach sands have identified what appears to be a previously unknown metallic alloy that formed during the immense heat and rapid cooling triggered by the 6 August 1945 explosion.The finding is less about rewriting the history of the bombing than expanding what scientists know about how matter behaves under conditions that are almost impossible to recreate.