Babak Kial said that a team of geologists has begun studies to shed light on part of the industry, art, and culture of the Achaemenid era.

“The mines of the white and azure stones used in the complex have already been identified by experts, and when the black stone mines are discovered, the project will be completed,” he said.

“After the identification of the original location of the black stone mines, experts will be able to learn about the methods of stone extraction used in ancient times, and (these sites) could be a good source (for materials) for additional renovations of the complex.

“Previous studies on the stone structures of the Achaemenid era indicate that the experts of those years used to make several holes in a part of a large rock and placed pieces of wood inside the holes. They later ran water into the holes, which helped them remove the piece from the rock,” he noted.