The Yemeni Corner of the Ka’bah


My question is regarding The Holy Kabaa, i went for Umrah two years ago and luckily i peform the tawaf very close to the walls of Kabaa. To my astonishemnt I saw that the Yemeni side of Kabba had a strange stone like object with marks on it. I wish to know what this object is, what is the name of it, and are we allowed to kiss it, the same way we kiss the Black stone.