The difficulty of beta tricalcium phosphate (b-TCP) crystallization in aqueous media opens the question whether b-TCP can be produced using an alternative pathway. Amorphous calcium phosphate (ACP) is metastable in an aqueous environment and prefers a more stable apatite phase. Others have transformed a crystallized calcium deficient hydroxyapatite (Ca-def HAp) into b-TCP, but automatic transformation from ACP to Ca-def HAp followed by transformation to b- TCP has not been addressed. This work shows the formation of Ca-def HAp after different aging times of ACP and the subsequent transition to b-TCP. An amorphous phase with a Ca/P ratio of 1.5 was synthesized, rinsed, filtered and excess fluid removed for maturation. The resulting apatite was monitored with X-ray diffraction at different temperatures. Heating at 700 oC then investigated the transition to b-TCP. It was found that Ca-def HAp formed at short aging times produced a combination of alpha and beta phases, but a longer aging time led to pure b-TCP.