Important bentonitic deposits are present in Porto Santo Island, part of the Madeira Archipelago. Several locations were selected and samples were collected and characterised. The bentonite obtained at Serra de Dentro (SD) was selected for further laboratorial work. The fine fraction of SD bentonite was purified using several methods and the sodium homoionic form was prepared. This was the starting material used in the three generic types of modifications: metal exchange, acid activation and pillaring. These modifications produce materials with markedly different acidic (e.g. Brönsted and/or Lewis acidity), textural (e.g. increase of the surface area and active site accessibility) or structural (e.g. creation of permanent porous structures) properties. The wide range of materials obtained (including reference clays counterparts) was characterised in terms of chemical, structural, textural and catalytic properties. Limonene is an important raw material produced in Portugal, and its aromatisation reaction was chosen for the catalytic characterisation of the clay catalysts prepared.