Poorly crystalline Al and Fe oxides and allophane
, which are relatively common in tropical soils, especially soils formed in recent volcanic ash, are known to interact intimately with organic matter, increasing its stability against decomposition (Tom et al.
137]Cs far more tightly than did the other clay minerals (fresh biotite, illite, smectite, kaolinite, halloysite, allophane
, and imogolite).
In fact, it is a flat coating of a blue color caused by overflowing allophane
Laser diffraction grain-size characteristics of Andisols in perhumid Costa Rica: the aggregate size of allophane
Statistical correlation between allophane
content and index properties for volcanic cohesive soil".
The key ingredient: allophane
, a micro-porous natural clay.
, aluminum, and organic matter accumulation across a bioclimatic sequence of volcanic ash soils of Argentina.
2003), whereas allophane
soil derived from volcanic ash is dispersed under high pH conditions (Wada 1985; Horikawa et al.
However, orthopyroxene, olivine and mangnetite were also detected in contaminated soils including allophane
and quartz (Table 2).
In general, the soils are not well developed and have originated from volcanic ashes (Andisol soils) with a high content of allophane
The presence of allophane
suggests the volcanic ash spread over a great part of Santa Cruz and Reef Islands in the recent past but that it has since been eroded from the steeply ridged landscapes and remains only on stable, more or less level land as a vestigial cover' (Wall and Hansell 1976:37).
Medium-lustrous blue microcrystals of vauxite form drusy crusts and arcing, hemispherical crests on fragile matrix composed of thin white casts after vanished spheres of--probably--wavellite; in another specimen style from the same find, vibrantly bright blue vauxite druses cover clayey matrix pieces made mostly of allophane