pietra dura

/P IY1 T R AH0 D UH0 R AH0/
noun
  1. 1

    Hard and fine stones in general, as used for inlay etc. and distinguished from the softer stones used in building.

    โ€œA Florentine mosaic is a familiar instance of work in pietra dura, though the ground may be soft marble.โ€

Source: https://en.wiktionary.org/wiki/pietra%20dura