Luminescence spectroscopy of Cr³⁺ and Mn²⁺ in spodumene (LiAlSi₂O₆)

Luminescence emission and excitation spectra of a number of natural spodumene crystals have been measured at temperatures down to 12 K. Both Cr³⁺ and Mn²⁺ centres were identified; Mn²⁺ is shown to be mainly in Li-sites rather than Al-sites and gives rise to a broad emission centred at 600 nm. In most spodumenes Cr³⁺ R-line emission with phonon sideband is observed at temperatures below 100 K. In the more Mn-rich crystals multiple R₁ lines are seen at temperatures below about 40 K, but in Cr-rich crystals only one R₁ line is observed and Cr³⁺ emission is evident at room temperature.