Argon-argon dating

Argon-argon dating of Vesuvius sanidine lands eight years from Pliny's eruption date

Berkeley and Padua geochronologists dated eight crystals from Vesuvius to 1,938 years, plus or minus 13, against a recorded age of 1,946 years. The same eruption date let them measure potassium-40's decay twice as precisely. Carbon-14 and uranium-lead results can now be checked against that constant.