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Carbon dioxide (CO₂) is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at Clinton Creek, Yukon Territory, and Cassiar, British Columbia, Canada. Accelerated weathering is attributed to a dramatic increase in surface area, which occurs during the milling of ore. We provide a detailed account of the natural process of carbon trapping and storage as it occurs at Clinton Creek and Cassiar, including mineralogy, modes of occurrence, methods of formation for carbonate alteration, light stable isotope geochemistry, and radiocarbon analysis. Powder X-ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite [MgCO₃·3H₂O], dypingite [Mg₅(CO₃)₄ (OH)₂·5H₂O], hydromagnesite [Mg₅(CO₃)₄(OH)₂·4H₂O], and less commonly lansfordite [MgCO₃·5H₂O]. Textural relationships suggest that carbonate …