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A microbial mineral carbonation trial was conducted at the Woodsreef Asbestos Mine (NSW, Australia) to test cyanobacteria-accelerated Mg-carbonate mineral precipitation in mine tailings. The experiment aimed to produce a carbonate crust on the tailings pile surface using atmospheric carbon dioxide and magnesium from serpentine minerals (asbestiform chrysotile; Mg₃Si₂O₅(OH)₄) and brucite [Mg(OH)₂]. The crust would serve two purposes: Sequestering carbon and stabilizing the hazardous tailings. Two plots (0.5 m³) on the tailings pile were treated with sulfuric acid prior to one plot being inoculated with a cyanobacteria-dominated consortium enriched from the mine pit lakes. After 11 weeks, mineral abundances in control and treated tailings were quantified by Rietveld refinement of powder X-ray diffraction data. Both treated plots possessed pyroaurite [Mg₆Fe₂(CO₃)(OH)₁₆·4H₂O] at 2 cm depth, made visible by its orange-red color. The inoculated plot exhibited an increase in the hydromagnesite [Mg₅(CO₃)₄(OH)₂·4H₂O] content from 2–4 cm depth. The degree of mineral carbonation was limited compared to previous experiments, revealing the difficulty of transitioning from laboratory conditions to mine-site mineral carbonation. Water and carbon availability were limiting factors for mineral carbonation. Overcoming these limitations and enhancing microbial activity could make microbial carbonation a viable strategy for carbon sequestration in mine tailings.