IMOGOLITE AND PROTO- IMOGOLITE IN AN ITAL IAN SOIL DEVELOPED ON VOLCANIC ASH

ABSTRACT 9 Imogolite has been identified in small amounts in clays from a soil profile developed on pyroclastics of tephrite-bassanite composition. The major part of the fine clay was an allophanic material termed proto-imogolite, characterized by an infrared spectrum with some of the features given by imogolite, including a well-developed band at 346 cm- ~. Similar products have been obtained in the laboratory. IDENTIF ICAT ION OF IMOGOLITE In a study of the andosols of Vulture (province of Potenza, Southern Italy) Violante & Violante (1973) found evidence for a fibrous component in the clay fraction of the A 1 horizon of a profile developed on pyroclastic materials of tephrite-bassanite composition, located at about 1280 m above sea level under fir forest. Further examination of clays from this profile by high resolution electron microscopy (Fig. 1A) and electron diffraction (Fig. 1B) has confirmed that this fibrous clay is indeed imogolite, exhibiting its typical tubular morphology and characteristic diffraction pattern (McHardy, 1971). Identifica-tion of imogolite was achieved most readily by examining the clays (< 1 pm) dispersed in water acidified to pH 3.5 with HC1, from soil previously treated with HzO2 and water