Impasto is a type of coarse Etruscan pottery. The defining characteristic is that the clay contains chips of mica or stone.[1]
In G.A. Mansuelli's, The Art of Etruria and Early Rome (1964), the term "impasto pottery" is described in the following way: "Ceramic technique characteristic of hand-worked vases. By 'impasto pottery' is generally meant that of pre-historic times, of the Iron Age or later, made of impure clay with silica content." (p. 236)