Imogolite and Allophane Formed in Saprolite of Basalt on Maui, Hawaii*

K. Wada, T. Henmi, N. Yoshinaga and S. H. Patterson
Faculty of Agriculture, Kyushu University, Fukuoka, Japan
Faculty of Agriculture, Ehime University, Matsuyama, Japan
U.S. Geological Survey, Beltsville, Maryland 20705, U.S.A.
* The name imogolite was approved by AIPEA Nomenclature Committee at its Tokyo meeting (Clays and Clay Minerals 19, 131 (1971).

Abstract: Inorganic gel and allophane collected from basaltic saprolite on Maui, Hawaii, and studied by Patterson in 1964 were reexamined. The main constituent of the gel is imogolite, and gibbsite and allophane are the minor constituents. Electron and X-ray diffraction patterns, DTA curve, and an infrared spectrum of the gel are characteristic of imogolite. The allophane is virtually noncrystalline to X-rays but contains a small amount of imogolite in relatively short threads. High-resolution electron micrographs indicate differences in structural organization between allophane and imogolite and suggest crystallization of imogolite from allophane.

The occurrence of imogolite as a weathering product has been reported in many localities from pyroclastic materials but not from massive rocks. Probably the exceptionally high rainfall, excellent subsurface permeability of the weathered material, and the low pH and high organic content of the leaching solution provide favorable conditions for formation of imogolite from basalt on Maui.

Clays and Clay Minerals; December 1972 v. 20; no. 6; p. 375-380; DOI: 10.1346/CCMN.1972.0200605
© 1972, The Clay Minerals Society
Clay Minerals Society (www.clays.org)