The 120 lead ingots, each weighing about 33 kilograms, come from a larger load recovered 20 years ago from a Roman shipwreck, the remains of a vessel that sank between 80 B.C. and 50 B.C. off the coast of Sardinia. As a testimony to the extent of ancient Rome's manufacturing and trading capacities, the ingots are of great value to archaeologists, who have been preserving and studying them at the National Archaeological Museum in Cagliari, southern Sardinia. What makes the ingots equally valuable to physicists is the fact that over the past 2,000 years their lead has almost completely lost its natural radioactivity. It is therefore the perfect material with which to shield the CUORE (Cryogenic Underground Observatory for Rare Events) detector, which Italy's National Institute of Nuclear Physics (INFN) is building at the Gran Sasso laboratory.
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(image credit: INFN/Cagliari Archeological Superintendence)