Resonant anomalous x-ray reflectivity near the Pt L(III) edge simultaneously revealed the geometric and spectroscopic structures of Pt(NH(3))(4)(2+) ions adsorbed at the quartz(100)-water interface. The derived Pt geometric subprofile shows two discrete "outer-sphere" adsorbed layers, and the interface-specific x-ray absorption edge profile exhibits a significant white-line enhancement compared to the bulk-solution species.