Ion-adsorption clay deposits (IACD) have recently gained global attention as an important source of heavy rare earth elements (HREE). Although the ore grade is relatively lower than in hard-rock deposits, REE in IACDs are loosely adsorbed onto clay minerals. This makes extraction simpler, cheaper, and less energy intensive.

IACD mining is commonly done through in-situ leaching with ammonium sulphate. In this process, the leaching solution is injected into the ground, and the REE-rich pregnant solution is collected in ponds. Later, the collected liquid then undergoes purification and precipitation processes to produce REE carbonates as the final product. However, the simplicity of this method also makes IACDs vulnerable to informal and unregulated mining. In addition, the mining process is highly chemical-intensive and poses risks to the environment, including soil degradation and water contamination. This highlights the need for regular monitoring of the IACD mining activities.

The rapid mining expansion of IACD can be observed in localised areas in Southeast Asia. This expansion has been documented through satellite imagery, while several reports have also raised concerns about environmental impacts. Because these mining areas are located in conflict zones, where field investigations are often not feasible, this makes remote sensing a key tool for monitoring.

So far, most monitoring studies of IACD mining have relied on high-resolution satellite imagery, which can map the location and extent of mine sites. However, these mining sites usually appear as clusters of circular treatment ponds containing materials and chemical reagents from different processing stages. While high-resolution imagery can detect the ponds, it cannot provide information about their chemical contents. This limitation highlights the potential of hyperspectral remote sensing, since hyperspectral data can capture chemical information of surface materials. However, current applications of hyperspectral remote sensing in mining have largely focused on minerals, leaving the spectral properties of chemical reagents and intermediate products poorly understood.