This is the mosque commissioned by Timur to be built near the Nabi Jirjis shrine/complex. The shrine itself (marked in the middle of the cemetary) is a Timurid-style complex, dating to 1393, that remains very damaged.
This mosque, also built in 1393, should be recognizable from the outside for its high circular dome and minaret with a pointed top (in the Turkish style). It supposedly houses the minbar and the main mihrab that were transplanted from the Nabi Jirjis tomb chamber at the time of construction. In 1910, after a major earthquake, the Timurid dome collapsed and was re-built with stone following Mosul building techniques.
Source: http://archnet.org/library/sites/one-site.tcl?site_id=7828