Mineralogical Characterization of Iron Ore Overburden: Sustainable Soil Remineralization through Circular Mining

Abstract

Aims: This research investigates the mineralogical composition of mining waste aiming clarifying its applicability as soil remineralizers through accelerated rock weathering. The validation parameters are those described in the normative instructions of the Ministry of Agriculture and Livestock and Embrapa in Brazil. Study Design: This proposal, based on circular economic principles, seeks to transform waste into agricultural inputs, fostering sustainable farming. The study characterizes compact shale, phyllite, and dolomitic itabirite overburden to evaluate their feasibility as soil remineralizers according to legal criteria. Place and Duration of Study: The study was conducted in Minas Gerais state, Brazil, with sample collection from the Itabira Complex and Pico Mine. The research was carried out over a defined period, including field sampling, laboratory processing, and data analysis. Methodology: Samples were collected from Itabira Complex and Pico Mine, processed, and subjected to particle size distribution, chemical, and crystallographic analyses. Results: Particle size distribution results showed a high proportion of fine particles, supporting gradual nutrient release, improved soil structure, porosity, and water retention. Crystallographic analysis identified minerals like chlorite, calcite, albite, and quartz in compact shale, while dolomitic itabirite had high hematite and quartz concentrations. Compact phyllite featured quartz and mica (muscovite) with significant potassium content. Chemical analysis revealed that compact shale meets the Ministry of Agriculture, Livestock, and Supply (MAPA) criteria for K2O+CaO+MgO concentration, indicating potential agricultural use. However, high quartz content in all samples limits their effectiveness as soil correctives, as quartz does not neutralize soil acidity. Despite this, iron ore overburden can improve soil structure, retain water, and support essential biogeochemical processes, particularly in conservation agriculture. Heavy metal levels in samples are within MAPA’s safety limits for agricultural use. Conclusion: The study concludes that iron ore overburden, especially compact shale, holds potential as soil remineralizers, though complementary practices are needed for optimal effectiveness.