Tiny Hiroshima Grain Reveals a Novel Silicon-Rich Iron Alloy

A glassy bead from Hiroshima Bay contains a microscopic grain that preserves a previously unknown silicon-rich alloy of iron, chromium, nickel, manganese, molybdenum, silicon, and aluminum, formed when city materials vaporized in the fireball and cooled rapidly. Using single-crystal X-ray diffraction, researchers found an ordered AlAu4-type structure, an unusual arrangement for iron-rich alloys, suggesting the blend of materials from urban debris can crystallize into exotic, highly ordered phases in seconds. While this could aid nuclear forensics by linking grains to blast conditions and temperatures, the finding is based on a single tiny grain and is not yet a practical alloy recipe.