Graph 17.4. EPR isotopic plot and EPR Intensity of the 11 black marble column shafts. Graph: D. Attanasio.

From Oplontis: Villa A ("of Poppaea") at Torre Annunziata, Italy. Volume 2. The Decorations: Painting, Stucco, Pavements, Sculptures by John R. Clarke and Nayla K. Muntasser