Abstract: The unit-cell characteristics and structures of sepiolite, ferri-sepiolites (xylotile, mountain wood, gunnbjarnite), loughlinite and palygorskite (attapulgite) and their structural relationships are discussed. The chemical, morphological and thermal properties are explained by their structures. The unit-cell characteristics and structures of sepiolite “anhydride”, loughlinite “anhydride” and palygorskite “anhydride” are given. Under low water vapor pressure the phase transformations sepiolite to sepiolite “anhydride” and palygorskite to palygorskite “anhydride” are reversible. It was not possible to synthesize sepiolite in the system MgO-SiO2-H2O under confined pressure within a range of 80° to 300°C
The possibility of the application of sepiolite and related compounds in industry, specially in the automobile industry, is referred to.