[alex_posat]

For the Rock Salt ceramic Structure, with a coordination number of 6, I'm told that the number of cations and anions is 4 of each. But this does not make sense to me! From observation, it looks like there is about 12 or 13 of each, and not 4.

Could you explain this?

(for a picture: http://www.tkk.fi/Units/AES/projects/prlaser/thesis/img38.png )

[Yggdrasil]

Since ions on the vertices are shared between eight unit cells, they count for 1/8th each.  Similarly, ions on the edges are shared by four different unit cells and count for 1/4th each, and ions on the faces are shared by two unit cells and count for 1/2 each.  With this in mind, try re-counting.