Direct detection of spodumene, the most economically important lithium ore mineral, remains challenging using conventional hyperspectral remote sensing approaches that rely solely on VNIR-SWIR data. These typically capture spectral responses from phyllosilicate alteration or weathering products rather than spodumene itself. This presentation demonstrates that while spodumene exhibits diagnostic Reststrahlen bands at approximately 9.05 μm and 10.4 μm and an interband peak at 10.1 μm in the LWIR enabling direct detection, the addition of SWIR data is critical for identifying pegmatite-associated minerals including white micas (muscovite, lepidolite), clays, and Al-OH phyllosilicates that provide essential context for interpretation and mapping of alteration assemblages.

We present case studies from Arizona lithium pegmatite projects (Whistlejacket and Midnight Owl) utilizing SpecTIR’s fully integrated VNIR/SWIR/LWIR airborne hyperspectral system, demonstrating analytical approaches for extracting spodumene signatures from mixed pixel spectra where common pegmatite minerals exhibit overlapping LWIR features near 9.1 μm.

Decision-tree analytics targeting Reststrahlen band positions successfully differentiated spodumene-bearing pegmatites from barren pegmatites and phyllic alteration assemblages, while combined VNIR/SWIR/LWIR wavelength analysis revealed internal pegmatite zonation patterns including albite-rich zones, mica distributions, and ENE-trending mineralized zones at Midnight Owl.

Critically, even in the absence of direct spodumene detection, systematic mapping of pegmatite zonation using quartz, feldspar (albite), and white mica signatures from integrated LWIR-SWIR data provides a robust indirect exploration approach for identifying prospective LCT pegmatites, as demonstrated at Whistlejacket where mineral assemblage mapping successfully prioritized targets for field verification.

Additional examples from Australia (successful direct detection in tailings, stockpiles, and in situ) and Canada (attenuated LWIR response due to vegetation and lichen requiring greater reliance on SWIR-based zonation mapping) illustrate both capabilities and environmental limitations.

Key findings demonstrate that while LWIR data enables direct spodumene detection where conditions permit, effective LCT pegmatite exploration in all environments demands a fully integrated multi-wavelength approach where SWIR data for mica and clay mapping combines with LWIR data for silicate framework minerals to characterize pegmatite zonation, differentiate fertile from barren systems, and guide targeted field verification even when spodumene’s low modal abundance (<20%) and spectral mixing preclude direct detection.