Mineralogical transformations of spodumene concentrate from Greenbushes, Western Australia. Part 1: Conventional heating

• Evidence of mineralogical transformations is presented in unprecedented level of detail.
• β-Spodumene formation results in increased surface area and reduced particle size and SG.
• XRD spectra provide evidence of γ-spodumene formation between 950 °C and 1100 °C.
• Structural change first observed at 950 °C after 30 min are completed at 1100 °C in 10 min.

Spodumene is a lithium aluminium silicate which can exist in α, β and γ modifications. Phase transformations of spodumene concentrate from the beneficiation plant in Greenbushes, Western Australia, were studied under a conventional method of heating. Spodumene concentrate was heated in a muffle furnace at 800, 850, 900, 950, 1000, 1050 and 1100 °C for 10, 20, 30 and 60 min in order to evaluate the effect of temperature and heating time on the amount of α-spodumene converted to β-spodumene, and also to assess the possibility of γ-spodumene formation. Structural changes were first observed after heating at 950 °C for a minimum of 30 min. Lower temperatures or residence times did not result in evident phase change while higher temperatures or residence times increased the extent of the phase change. At 1100 °C and for times longer than 10 min, the transformation from α-spodumene to γ and β-spodumene was complete. It also resulted in volumetric expansion of the sample and change of colour from beige to ice white. X-ray diffraction spectra and scanning electron microscope images also provided evidence of γ-spodumene formation from 950 °C up to 1100 °C. Samples were analysed in order to investigate changes in their physical properties. The results revealed that specific surface is directly related to the amount of β-spodumene which forms at higher temperatures. On the other hand particle size and specific gravity reduced with formation of more β-spodumene.