CRYSTAL CHEMISTRY AND SPECTROSCOPY OF JADEITE

Jadeite, nominally NaAlSi₂O₆, has long been observed to emit green, blue, or red luminescence. The chemical origin of these phenomena is currently unknown. The goal of this study is to determine the chemical activators of luminescence in Na-rich pyroxene through the implementation of four analytical techniques. Thirty-two samples of jadeite from Guatemala, Burma, California, Russia, and Japan were selected from the collections of the Smithsonian NMNH. These samples were analyzed using the electron microprobe for major elements, Mössbauer spectroscopy for Fe³⁺/Fe²⁺, ICP-MS for trace and minor elements, and cathodoluminescence (CL) for emission energies. The complete chemical data acquired from these techniques are used to examine the variations in jadeite chemistry, including their Fe³⁺ contents to paragenesis. CL analysis was conducted on 21 jadeite samples that emit predominately green luminescence, and work is in progress on samples that emit both red and/or blue luminescence. Prominent energy peaks were identified at 442 nm, 561-579 nm, and 682 nm. The source of jadeite's blue band at 442 nm is hypothesized to be due to the presence of one or more unknown defect centers. However, the CL analyses of tectosilicates have concluded that peaks in the 400 nm-range are caused by the presence of Al³⁺ or Eu²⁺, and we are investigating this possibility. The green peaks observed between 561-579 nm are most likely due to Mn²⁺ ions, thus causing the samples to glow a canary-yellow green. This Mn²⁺ peak is also observed in many other silicate minerals, including feldspars. The red peak at 682 nm may result from the presence of Mn²⁺, Cr³⁺, and/or Fe³⁺. Mössbauer data acquired as part of the current study will help to further constrain the activators of red luminescence phenomena.