The present research work developed synthetic hydroxyapatite from chicken eggshell (Gallus gallus) evaluating the influence of calcination time from 1 hour to 4 hours under a constant temperature of 1000°C on behavior of grain size and index of crystallinity. For this, the following procedure was followed: Cleaning of the egg shell and separation of the membrane, drying, pulverizing, sieving, calcining at 800°C for 6 hours, phosphating and calcining at 1000°C. The samples were characterized through X-ray diffraction using the Rigaku brand diffractometer, Miniflex 600 model. The results showed that the highest crystallinity index is obtained under a calcination time of 2 hours with a value of 58.85% and a size of 61,510 nm grain; however, the smallest grain size corresponds to a calcination time of 3 hours with a value of 57.740 nm and a crystallinity index of 57.33%. This shows that t...