%0 Journal Article
%T Myriad Mapping of nanoscale minerals reveals calcium carbonate hemihydrate in forming nacre and coral biominerals.
%A Schmidt CA
%A Tambutté E
%A Venn AA
%A Zou Z
%A Castillo Alvarez C
%A Devriendt LS
%A Bechtel HA
%A Stifler CA
%A Anglemyer S
%A Breit CP
%A Foust CL
%A Hopanchuk A
%A Klaus CN
%A Kohler IJ
%A LeCloux IM
%A Mezera J
%A Patton MR
%A Purisch A
%A Quach V
%A Sengkhammee JS
%A Sristy T
%A Vattem S
%A Walch EJ
%A Albéric M
%A Politi Y
%A Fratzl P
%A Tambutté S
%A Gilbert PUPA
%J Nat Commun
%V 15
%N 1
%D 2024 Feb 28
%M 38418834
%F 17.694
%R 10.1038/s41467-024-46117-x
%X Calcium carbonate (CaCO3) is abundant on Earth, is a major component of marine biominerals and thus of sedimentary and metamorphic rocks and it plays a major role in the global carbon cycle by storing atmospheric CO2 into solid biominerals. Six crystalline polymorphs of CaCO3 are known-3 anhydrous: calcite, aragonite, vaterite, and 3 hydrated: ikaite (CaCO3·6H2O), monohydrocalcite (CaCO3·1H2O, MHC), and calcium carbonate hemihydrate (CaCO3·½H2O, CCHH). CCHH was recently discovered and characterized, but exclusively as a synthetic material, not as a naturally occurring mineral. Here, analyzing 200 million spectra with Myriad Mapping (MM) of nanoscale mineral phases, we find CCHH and MHC, along with amorphous precursors, on freshly deposited coral skeleton and nacre surfaces, but not on sea urchin spines. Thus, biomineralization pathways are more complex and diverse than previously understood, opening new questions on isotopes and climate. Crystalline precursors are more accessible than amorphous ones to other spectroscopies and diffraction, in natural and bio-inspired materials.