Which stone was used to construct the buildings at Persepolis?

The buildings at Persepolis were constructed using a dark gray stone sourced from the adjacent mountain, known as Kūh-e Raḥmat ("Mount of Mercy").1

This stone was cut with high precision into large blocks and laid without the use of mortar. The material was often polished to achieve a surface similar to marble. While these stone elements—such as columns, door jambs, and window frames—have survived, other parts of the structures, including enclosure walls, were originally built of mud brick.12