MÖSSBAUER STUDY OF NATURAL GLASSES : LIPARI AND TEOTIHUACAN OBSIDIANS F. Chavez-Rivas, J.R. Régnard et J. Chappert J. Phys. Colloques, 41 C1 (1980) C1-275-C1-276 DOI: 10.1051/jphyscol:1980196