Looks like 12
do a web search on "tausonite coordinate oxygen" and pick the "Crystal Structures" link for a good diagram.
Tausonite, a mineral composed of Sr, O, and Ti, has the cubic unit cell and the chemical formula is SrTiO3.....
Ti is coordinated by 6 O atoms, because the Ti is located at the center of the unit cell. To see the full coordination environment of the other ions, we have to consider neighboring unit cells. How many oxygens coordinate to Sr?
2 answers
Apparently Steve can't copy links. Here it is.
http://dissertations.ub.rug.nl/FILES/faculties/science/2004/o.f.goebel/appendix.pdf
http://dissertations.ub.rug.nl/FILES/faculties/science/2004/o.f.goebel/appendix.pdf