Fig. 4.

The nanocrystalline structure of the prismatic layer in Pinctada fucata. The image and spectra data were acquired as described in Fig. 2. An animated version of this stack is shown in Movie S2. (A) Average image showing one prism near the prismatic-nacre boundary of the shell. The boundary itself is the darker, thick organic layer at the top, and two vertical interprismatic organic layers separate the central prism from the adjacent ones on the left- and the right-hand sides. The central prism extends for 100–300 μm and is only partially displayed in this 30-μm field-of-view image. (B) Spectra extracted from the 30-nm pixels indicated in A and correspondingly colored, selected within the central prism. The spectra clearly show three different crystal orientations. Table 2 shows the values for the angles obtained from these data.