Omnisphere contains a best of "Heart of Africa" and "Vocal Planet" including Tuvan throat singers. Omni is so vast that the more I use it the more I find I can't say enough good things about it. The original Spectrasonics vocal discs though seem to be so extensive and deep that they are worth the price if that is your musical focus.
Voices of Passion by EastWest Quantum Leap is also stellar -- though no African vocalist.
Ethno by MOTU I believe also has some "ethnic" chanting.
Tonehammer has 3 libraries with ethnic female vocals.
We actually just released a new female vocal library the other day that is built primarily around African vocal styles and chanting, with added gospel, R&B and jazz elements. It's called Forgotten Voices: Terrie