10.1021/jp503700g.s011 Ross T. DeVol Ross T. DeVol Rebecca A. Metzler Rebecca A. Metzler Lee Kabalah-Amitai Lee Kabalah-Amitai Boaz Pokroy Boaz Pokroy Yael Politi Yael Politi Assaf Gal Assaf Gal Lia Addadi Lia Addadi Steve Weiner Steve Weiner Alejandro Fernandez-Martinez Alejandro Fernandez-Martinez Raffaella Demichelis Raffaella Demichelis Julian D. Gale Julian D. Gale Johannes Ihli Johannes Ihli Fiona C. Meldrum Fiona C. Meldrum Adam Z. Blonsky Adam Z. Blonsky Christopher E. Killian Christopher E. Killian C. B. Salling C. B. Salling Anthony T. Young Anthony T. Young Matthew A. Marcus Matthew A. Marcus Andreas Scholl Andreas Scholl Andrew Doran Andrew Doran Catherine Jenkins Catherine Jenkins Hans A. Bechtel Hans A. Bechtel Pupa U. P. A. Gilbert Pupa U. P. A. Gilbert Oxygen Spectroscopy and Polarization-Dependent Imaging Contrast (PIC)-Mapping of Calcium Carbonate Minerals and Biominerals American Chemical Society 2014 PIC calcium carbonate minerals nacre calcite contrast recording XANES spectra Mytilus californianus shells calcium carbonate Calcium Carbonate Minerals crystal spectroscopy spectromicroscopy CaCO 3 biominerals information vaterite aragonite 2014-07-17 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Oxygen_Spectroscopy_and_Polarization_Dependent_Imaging_Contrast_PIC_Mapping_of_Calcium_Carbonate_Minerals_and_Biominerals/2273632 X-ray absorption near-edge structure (XANES) spectroscopy and spectromicroscopy have been extensively used to characterize biominerals. Using either Ca or C spectra, unique information has been obtained regarding amorphous biominerals and nanocrystal orientations. Building on these results, we demonstrate that recording XANES spectra of calcium carbonate at the oxygen K-edge enables polarization-dependent imaging contrast (PIC) mapping with unprecedented contrast, signal-to-noise ratio, and magnification. O and Ca spectra are presented for six calcium carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite, and both hydrated and anhydrous amorphous calcium carbonate. The crystalline minerals reveal excellent agreement of the extent and direction of polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong for aragonite, calcite, and vaterite. In natural biominerals, oxygen PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite crystals at the nacre–prismatic boundary and the narrowest calcite needle-prisms. In the tunic spicules of Herdmania momus, O PIC-mapping revealed the size and arrangement of some of the largest vaterite single crystals known. O spectroscopy therefore enables the simultaneous measurement of chemical and orientational information in CaCO<sub>3</sub> biominerals and is thus a powerful means for analyzing these and other complex materials. As described here, PIC-mapping and spectroscopy at the O K-edge are methods for gathering valuable data that can be carried out using spectromicroscopy beamlines at most synchrotrons without the expense of additional equipment.