This is claimed by some to be the first mosque in the Sahara Desert. Kufic. This congregational mosque was subsequently partially excavated by Ziegert and Abdussalam (1969, 1973) and more substantially by Abdussaid (1979; see also the summary by el-Mahmoudi 1997). It is one of the largest mosques known in the Central Sahara, especially significant given its presumed date. The nearby tombs have some inscriptions using the Kufic script (font).
A sample from the mud brick of the mosque reveals that the mosque, was built around. AD 670-857 (OxA-26744 calibrated at 95.4%). This would fit with the dates of the other mosques in Africa that used a similar Qibla direction. (see the Graveyard of Sidi ‘Ukba)
For more information, see the paper: The origins and development of Zuwīla, Libyan Sahara: an archaeological and historical overview of an ancient oasis town and caravan centre, by David J. Mattingly, Martin J. Sterry & David N. Edwards (Azania: Archaeological Research in Africa, 2015)