Morphological changes due to the weathering of the main mineral species present in fersialitic soils on volcanic materials (Canary Islands), are studied by polarising microscope. Two alteration sequences are given for volcanic glass depending on the weathering conditions, determined by percolating water regimes. Feldspars alteration (sanidine and plagioclase) leads in its last step to the apparent total leaching of the mineral. Olivines undergo a peripheric alteration into iddingsite, and augites and hornblendes into goethite and hematites.

Peer reviewed