Still the standard brick shape of criss-crossing rectangular prisms. Eurasians and Amerindians often didn't bother with mortar if it wasn't needed. Considering the amount of violence and lack of archaeology in Africa it seems like it would be hard to say if they lacked mortar technology of their own or not.
Re. Great Zimbabwe, my point was that brick was non-existent south of the Sahara before Arab and European influence. The use of mortarless stone, of course, goes back an indeterminate amount of time into the paleolithic.
Mortarless stone-laying can be very strong. Not only are there countless examples going back to before the dawn of civilization (and in pre-Columbian times---Cuzco is a stunning example), I've personally laid drystone walls that are for the ages...
The First Peoples of the American SW, Meso-America, and Peru used adobe brick which was mortared with the same material as the brick, except wet. Also, drystone (think Anasazi)