Coral is a natural biomaterial used nowadays frequently in medical applications. Our recent studies show that a coral implanted in bone tissue is gradually transformed to become a neoformed bone. In some special cases, high temperature has to be used as sterilization mean instead of gamma or electron irradiations. Here, we perform this method and we analyse cristalline behaviourvs. temperature with X-rays diffractions. We show that coral aragonite and mineral pure aragonite have two different temperatures for aragonite-calcite phase transition: 300° and 470°C.