Were there black slave owners

Not in the USA because to be a slave you had to have black blood in your system which means that if you had black blood in your system you were not considered human but cattle and therefore a slave. However outside America there were plenty of black slave traders. And black tribesmen involved in selling other black people into slavery. The whites were the end users; the blacks and the Arabs were the suppliers.

This is not true at all. William Ellison was a Black slave owner in South Carolina and the majority of slave owners in New Orleans were Black. William Ellison, whose slave name was April, became a slave magnate and expanded his business throughout the south, from South Carolina to the Mississippi River. I would strongly suggest you google "Black Slave Owners" and I guarantee that you will have a plethora of information.