Which building specifically? If talking about black stones; only what you can tell with detect magic and that roll is that the dark stone used for walls are from local foundry and sort local specialty. You can tell the black stones are not suitable for carving or making objects of art but it's very dense and hard when positioned right (simply said double hardness of said stone when impact comes from one specific direction). Reason why it's not suitable for art is because of how it fragments easily when going smaller sizes (having half of normal HP when going anything less than football size in measure).