What is meant by "stones of oil" and who are "the people of the stones of oil" mentioned in Hadith no. (3958) from Sunan Ibn Majah?

The hadith explains that the Prophet (peace be upon him) described to Abu Dharr severe future conditions such as widespread death to the extent that graves would be sold for garments, intense hunger that would prevent movement, and great slaughter that would drown the stones of the oil press in blood. In each case, he advised him to be patient and chaste. In times of tribulation and killing, he advised him to seclude himself, remain in his home, and not take up the sword. If someone entered upon him, he should surrender so that the killer would be the one to bear the sin. The stones of the oil press (Hijarat az-Zayt) are an area in Medina named for the blackness of its rocks. The Battle of al-Harra took place there during the time of Yazid ibn Mu'awiyah, after the people of Medina renounced their allegiance to Yazid due to his evil deeds and فسق (wickedness). Yazid then sent an army led by Muslim ibn Uqbah, who desecrated Medina and killed many of its people, including seven hundred memorizers of the Qur'an and three Companions.