In the present study, we investigated a number of Ca containing inorganic and biogenic (natural) materials as reagents for hydroxyapatite synthesis by modified wet chemical precipitation route. Phase, molecular, chemical analysis and morphology of hydroxyapatite powders as well as thermal stability and microstructure of hydroxyapatite bioceramics were investigated. Also reasons of color change of hydroxyapatite bioceramics after thermal treatment were examined. Synthesized hydroxyapatite powders from different Ca sources have different morphology and crystal size. This affects bioceramic microstructure and sintering behavior and the distinct color change after sintering. The chemical and physical properties of the CaO particles have a great influence on the quality of the synthesis product.