A single freeze cycle redirects iron mineral transformation

This dataset is for the paper entitled "A single freeze cycle redirects iron mineral transformation" by Luo T, Chen T, Thi, TMB, Behan J, Heterington C, Hanna K, Boily JF submitted to Science on December 21 2025, in revised form on April 1 2026 and in 2nd revised form on May 15 2026. Abstract: Polycrystalline ice concentrates mineral nanoparticles into liquid intergrain boundaries between growing crystals. Here we show that minutes of freezing seal iron mineral fate, accomplishing what normally requires months of aqueous aging. A single freeze–thaw cycle irreversibly transforms ferrihydrite, a ubiquitous iron oxyhydroxide, through converging mechanisms: freeze-concentration collapses electrostatic barriers, cryosuction strips hydration and generates MPa-scale pressures, and planar confinement compresses particles into mesocrystal-like assemblages. These forces drive olation and oxolation at particle contacts, forming permanent hydroxo and oxo bridges while retaining nanoscale primary particles. The resulting aggregates block dissolution–reprecipitation to goethite, instead transforming directly to hematite over months. Ice thus acts as a geochemical reactor, compressing condensation chemistry into minutes and redirecting iron mineral fate for years, with broad implications for cold-region biogeochemistry. The single MS Excel file contains raw or treated data for Figures 1-5 of the main text and Figs. S1-S20 of the Supplementary. Data include X-ray diffraction patterns, vibrational spectra, electron microscopy images, X-ray photoelectron spectra, thermogravimetric data, particle sizing measurements, and solution chemistry results,