**3.1 Chemical content**

The samples' quantitative chemical analyses are shown in **Table 2**. As observed there is a satisfactory agreement between the elements amount determined from the analyses and those introduced in the starting. As a consequence, the experimental formula was close to the theoretical ones. The SrþLaþNd <sup>P</sup>þSi molar ratios are very close to the theoretical value of 1.667 for stoichiometric apatite.
