Mollusk shells protect the animals that form and inhabit them. They are composites of minerals and organics, with diverse mesostructures, including nacre, prismatic calcite, crossed-lamellar aragonite, and foliated calcite. Twins, that is, crystals mirror symmetric with respect to their coherent interface, occurring as formation or deformation twins, are observed in all mollusk shell mesostructures but never within calcite prisms. Here, nanotwins and microwins within single calcite prisms are observed in different shells. Using Polarization-dependent Imaging Contrast (PIC) mapping with 20–60 nm resolution, twins are observed to be 0.2–3 µm thick layers of differently oriented and colored crystals with respect to the main prism crystal. Multiple twins are interspersed with the prism crystal, parallel to one another, and similarly oriented. When comparing images of calcite prisms and twins obtained by PIC mapping and by Electron Back-Scattered Diffraction (EBSD), the images correspond precisely. All twins are e-twin types, with 127° angular distance between c-axes. E-twins are the most common deformation twins in geologic calcite, as also observed here in Carrara marble. Location of all twins near the outer surface of all shells and e-twin type both suggest that twins within calcite prisms in mollusk shells result from deformation twinning.
Alvarez, Cristina Castillo, Grimsich, John L., Schmidt, Connor A., Lisabeth, Harrison, Voigtländer, Anne, & Gilbert, Pupa U. P. A. (2023). Calcite Twinning in Mollusk Shells and Carrara Marble. Advanced Functional Materials, 34(35). https://doi.org/10.1002/adfm.202304288
@article{osti_2228610,
author = {Alvarez, Cristina Castillo and Grimsich, John L. and Schmidt, Connor A. and Lisabeth, Harrison and Voigtländer, Anne and Gilbert, Pupa U. P. A.},
title = {Calcite Twinning in Mollusk Shells and Carrara Marble},
annote = {Mollusk shells protect the animals that form and inhabit them. They are composites of minerals and organics, with diverse mesostructures, including nacre, prismatic calcite, crossed-lamellar aragonite, and foliated calcite. Twins, that is, crystals mirror symmetric with respect to their coherent interface, occurring as formation or deformation twins, are observed in all mollusk shell mesostructures but never within calcite prisms. Here, nanotwins and microwins within single calcite prisms are observed in different shells. Using Polarization-dependent Imaging Contrast (PIC) mapping with 20–60 nm resolution, twins are observed to be 0.2–3 µm thick layers of differently oriented and colored crystals with respect to the main prism crystal. Multiple twins are interspersed with the prism crystal, parallel to one another, and similarly oriented. When comparing images of calcite prisms and twins obtained by PIC mapping and by Electron Back-Scattered Diffraction (EBSD), the images correspond precisely. All twins are e-twin types, with 127° angular distance between c-axes. E-twins are the most common deformation twins in geologic calcite, as also observed here in Carrara marble. Location of all twins near the outer surface of all shells and e-twin type both suggest that twins within calcite prisms in mollusk shells result from deformation twinning.},
doi = {10.1002/adfm.202304288},
url = {https://www.osti.gov/biblio/2228610},
journal = {Advanced Functional Materials},
issn = {ISSN 1616-301X},
number = {35},
volume = {34},
place = {United States},
publisher = {Wiley},
year = {2023},
month = {08}}
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); National Science Foundation (NSF)
Alam, M. N.; Blackman, Moses; Pashley, Donald William
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, Vol. 221, Issue 1145, p. 224-242https://doi.org/10.1098/rspa.1954.0017
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 379, Issue 2203https://doi.org/10.1098/rsta.2020.0437