Effects of Mn and Fe on the color and luminescence properties of spodumene

Abstract

Spodumene, a lithium-rich pyroxene mineral, exhibits a wide range of colors and distinctive luminescent properties, yet the mechanisms underlying its coloration and fluorescence remain incompletely understood. In this study, twelve natural spodumene samples of varying colors (purple, yellow, green, and nearly colorless) were systematically analyzed by modern testing technology. Color variation of the sample is primarily controlled by the Mn/Fe ratio, with purple tones corresponding to Mn/Fe > 1, yellow to green to Mn/Fe < 1, and colorless samples showing negligible Mn and Fe content. All samples exhibited two emission centers near 420 nm and 600 nm, attributed to lattice defects and the ₄T¹(4G) → ₆A¹(6S) transition of Mn²⁺, respectively. The 600 nm emission band is responsible for the observed orange-red fluorescence under long-wave UV light. Fluorescence intensity was negatively correlated with Fe content, and fluorescence lifetimes at 600 nm increased with Mn concentration, reaching approximately 4000 μs in Mn-rich samples. These findings not only clarify the synergistic role of lattice defects, Mn activators, and Fe quenchers in controlling the coloration and luminescence mechanisms of spodumene, but also offer a scientific foundation for engineering synthetic luminescent materials with targeted chromatic properties and for gemological enhancement strategies.