Fig. 3. STXM micrographs for an exterior aggregate region taken below (a) 281 eV and (b) above 290 eV the carbon absorption edge. Contrast in the C and mineral density is shown in the ratio micrographs (c) calculated fromlog [I/Io] where I =
(281 eV 282 eV) and Io =
(290 6 eV 291.5 eV).