What was the description of the rock that Moses struck?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It was a specific, well-known rock known to Moses. [Ibn ʿAbbās, Ibn Jubayr, Qatādah, ʿAṭiyyah, Ibn Zayd, Muqātil] They differed in its description with three opinions: (i) It was a square-shaped rock. [Ibn ʿAbbās] (ii) It was like the head of a bull. [ʿAṭiyyah] (iii) It was like the head of a sheep. [Ibn Zayd]

Saʿīd ibn Jubayr added: "This was the rock that ran off with Moses' clothes.* Gabriel came to him and said: 'Allah commands you to lift this rock; there is power in it for Me, and a miracle for you.' Whenever Moses needed water, he would strike it." (*see commentaries on Q 33:69)

1. He was commanded to strike any rock. Ibn al-Jawzī comments: The first opinion is stronger.