Quenched iron-enriched basalt (IEB) specimens with various additions were examined by X-ray diffraction and scanning electron microscopy to determine the phase equilibria and microstructural development in the waste form system. The Synroc titanate mineral-phase zirconolite (CaZrTi//2O//7) formed in the microstructure of many of the specimens. An optimum composition and cooling cycle for the development of the zirconolite phase in IEB were determined. Leach Specimens were prepared under these optimum conditions and tested via standard MCC-1 procedures. A Joule-heated glass melter was used to produce a 10-kg casting. The zirconolite that formed effectively scavenged all of the actinides examined except neptunium. The casting investigation indicated that the IEB-TiO//2/-ZrO//2 waste form can be processed in a Joule-heated glass melter.