The number and the structure of cross-links in type I collagen are different from each organ, therefore, orientation and diameter of type I collagen fibers are also different from each organ. When type I collagen is used as biomaterials for hard tissue regeneration, it can be considered that the characteristics and the quantity of newly created minerals in type I collagen are different depending on organs-derived. In this study, calcium phosphate were synthesized in type I collagen gels derived from pig skin or tendon and bovine bone, and the characteristics of obtained minerals were investigated. It was suggested that all the newly created products were octacalcium phosphate (OCP) in X-ray diffraction analysis. Furthermore, X-ray diffraction analysis showed that minerals obtained in bone collagen gel were significantly high in crystallinity compared with minerals obtained in skin and tendon collagen gel. However, the quantity of the newly created minerals in bone collagen decreased significantly compared with minerals obtained in skin and tendon collagen. Collectively these results suggest that the characteristics and quantity of minerals synthesized in type I collagen are depending on organ of origin.