Fig. 3. Transmission electron microscopy (TEM) of SHA samples: (a) TEM of Mn11-SHA, Arrow 1 indicates elongated crystallite with rounded head, Arrows 2 indicate oval features, and Number 3 indicates energy dispersive spectrum site (Fig. 4). Particle with apatite (100) d-spacing 0.81 nm indicates Mn11-SHA crystallites have apatite structure; (b) TEM of Fe-enriched particle found in Fe25-SHA, Arrow 1 indicates energy dispersive spectrum site (Fig. 4).