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Biomineralized structures are often used as indicators of environmental conditions in which they have grown. This study investigates the distribution of two trace elements, Mg and Na, commonly used in these environmental proxies, in the eggshells of seven different avian species to investigate the behavior of these elements in a mineralized system produced in a constant temperature environment where salinity is also strictly controlled. We used electron backscatter diffraction (EBSD) in conjunction with electron probe microanalysis (EPMA) to examine the eggshell structure to establish possible relationships between the crystallographic structures and the trace element distribution within each specimen as well as between species. A universal trend between species can be established for crystallographic structure and trace element distribution with some exceptions. Mg and Na vary across the eggshell profile in a carbonate system produced in a constant temperature environment, with links to crystallography remaining ambiguous. The reasons for variability in trace element distribution in such systems may therefore be more closely related to variation in organic distribution than merely environmental and physical crystallographic factors. The crystallographic data show the nucleation of small crystals on the mammillary caps with "fanning" of orientation until fusion of the mammillary caps to create large single crystals in the palisade layer with the elongation along the c-axis in the 〈0001〉 direction. The Mg and Na concentrations both decrease after nucleation but vary in their distribution and concentration between species after the nucleation stage of the shell.

Fine-scale structures of intact modern and fossil coralline skeletons were analysed to determine alteration to secondary cements and phases using electron backscatter diffraction (EBSD). EBSD analysis revealed secondary aragonite cements in endolithic borings in the modern skeleton and whole dissepiments of the fossil skeleton replaced by calcite, despite X-ray diffraction (XRD) bulk analysis of the general area suggesting only aragonite was present. Non-destructive, in situ screening of coral samples by EBSD analysis provides a valuable tool for assessing the extent of alteration and can determine which areas may produce more reliable climate proxy data

Aragonite nacre is commonly found in the shells of molluscs, while semi nacre has been observed in the shells of organisms from two phyla: the Brachiopoda and the Bryozoa. Calcite semi nacre and aragonite nacre display similar morphologies with laminae composed of tablets that grow by screw dislocation. This study uses electron backscatter diffraction to compare the crystallography of calcite semi nacre from the shell of the Craniid brachiopod NoVocrania huttoni with aragonite nacre from the shell of the bivalve mollusc Mytilus edulis. Semi nacre and nacre are similar in morphology but ultimately have different crystallography. In N. huttoni calcite semi nacre, the c-axis lies parallel to the laminae of the secondary layer of the shell. In comparison, the c-axis of aragonite nacre in M. edulis is orientated perpendicular to the laminae. The crystallography of calcite semi nacre in the secondary layer of N. huttoni is similar to the crystallography of skeletal ultrastructures produced by bryozoans, while it differs from the crystallography described in other brachiopod genera.

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