Authors: GOMES C S F MASSA M E

Citation: F. Gomes C S et E. Massa M, Allophane and spherulitic halloysite, weathering products of trachytic pumice fall-outs in the Caldeira Velha area (S. Miguel-Azores), Mineralogica et petrographica acta , 35-A, 1992, pp. 283-288