A type of ionic crystal structure in which the anions have a hexagonal close packed arrangement with cations in half the octahedral holes. The coordination number of the anions is 6 and the coordination number of the cations is 3. Compounds with this structure include TiO2, MnO2, SnO2, MgF2, and NiF2.
http://www.chemtube3d.com/solidstate/_rutile(final).htm An interactive version of the structure