Ferrous Mineral Index (FMI) is used to detect and map ferrous (iron-bearing) minerals on the Earth’s surface by analyzing reflectance from specific shortwave infrared wavelengths sensitive to iron content. It identifies minerals like hematite and goethite, which are common in iron-rich soils and rocks. FMI values range from 0 to +1, where higher values indicate a higher concentration of ferrous minerals, and lower values indicate minimal or no iron-bearing minerals. It is useful in geological mapping, mineral exploration, and soil characterization.