The crystalline properties are typically characterized by special kind of clay materials, allophane, imogolite, halloysite and ferrihydrite. Allophane is a round sphere (see figure below), extremely reactive (up to 800 square m per gram) but lacks the cohesion of typical clays found in other common soil types, such as smectite.

Water content
The soil is light and very porous. It can store large quantities of water, much more than any other soils except for organic soils (Histosols), often more than 100% on weight basis when saturated with water.

Organic matter
Andosols have a tendency to bind organic matter and therefore often contain much more organic materials than other soils under similar conditions.

Phosphorus fixation
The soils have a tendency to bind phosphorus so tightly that phosphorus fertilizers are often needed when growing crops on these soils.

Lack of cohesion
These soils often lack of cohesion and exhibit a property called phixotrophy, which mean they can all of a sudden start to behave like a liquid when they contain high amount of water. This can cause problems such as landslides and various engineering problems.

Allophane Profile 3: Iceland Summer1999

Last modified 11 March 2003 by IAK