Thermal Upgrading Effect: Saprolite versus Limonite

Fathan Bahfie*, Azwar Manaf*, Widi Astuti, Fajar Nurjaman, Erik Prasetyo, Diah Susanti

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The mineralogical properties of saprolite and limonite from Indonesia were investigated by X-ray diffraction, X-ray fluorescence, atomic absorption spectro-photometer, field-emission scanning electron microscopy, and differential thermal analysis. The percentages of Ni, Fe, Mg, Al, and Si in saprolite are given in 1.82, 30.47, 10–20, 4.86, and 8.1 wt%, and in limonite are 1.4, 50.5, 1.81, 4.86, and 16.5 wt%. Saprolite has 53.1% goethite, 38.3 % lizardite, 8.7 % silicate, and limonite has 94.4 % goethite and 5.6 % silicate. According to DTA, saprolite and limonite have the same phase transition from goethite to hematite at low temperatures (250 °C); at 900 °C the magnesioferrite crystallization for limonite and the crystallization of forsterite for saprolite, and the growth of ferronickel in 1150 °C; however, transformation of lizardite at 600–700 °C for saprolite is observed. It is a suitable phase to optimize nickel diffusion in iron. Furthermore, the thermal upgrading approach was utilized for limonite and saprolite at low temperatures.

Original languageEnglish
JournalTransactions of the Indian Institute of Metals
Publication statusAccepted/In press - 2024


  • Characterization
  • Limonite
  • Microstructure
  • Phase
  • Saprolite
  • Thermal upgrading


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