The common structure of uCOM (A, B) and iCOM (C) crystals, showing the Miller indices used by Wesson and colleagues (A) [18–20], Qiu and associates (B) [21–23], and the group of Hunter et al. (C) [24,25]. D, shows the system used in the present study, where the top, side and apical faces correspond, respectively, to the (100) (010) and (021) faces assigned by Tazzoli and Domeneghetti [26].