Rassoul (or Ghassoul) is a Moroccan lava clay used for washing and cleaning hair and skin. Its mechanism of action is simple it absorbs grease and cab maintain the hair lipid level without an excessive degreasing effect, avoiding the "rebound" phenomenon so frequently found with commercial shampoos.
Rassoul is a trioctahedral magnesium montmorillonite. Its properties are due to the crystal structure and presence of magnesium in octahedral layers and silicon in tetrahedral layers.
The swelling mechanism of Moroccan lava clay is as follows: when water is placed in contact with Rassoul, it is trapped between the clay platelets. As wetting progresses, the particles get considerably enlarged, and a characteristic cleavage appears along the layers, making the platelets dispersed, giving a colloidal suspension.
Besides van der Waals forces, commonly found in montmorillonite, Rassoul's absorption capacity can be explained also through the presence of electrostatic forces thanks to the polar character of the structure.
Moroccan lava clay also shows an important cation exchange capacity because of its high magnesium ion content. Thanks to its ability to neutralize calcium salts, Moroccan lava clay allows to avoid the formation of calcareous deposits on the hair.