Tourmaline of the elbaite-schorl series from the Himalaya Mine, Mesa Grande, California: A detailed investigation

Chemical, structural, infrared, optical, and Mossbauer spectroscopic data were obtained on tourmalines from gem pockets in the Himalaya mine, San Diego County, California, including a strongly color-zoned crystal. Calcium and Li abundances increase from core to rim, whereas Mn^(2+) and F increase, reach a maximum, and then decrease. Upon initiation of crystallization of lepidolite, F contents in tourmaline decrease. The black core is a Mn-bearing "oxy-schorl." The grayish-yellow, intermediate zone is Mn-rich "fluor-elbaite" that contains a relatively high Mn content with ~6 wt% MnO. The nearly colorless "fluor-elbaite" rim has the highest Li content of all zones. There is an inverse correlation between the lattice parameter a (for values ≥ 15.84 A) and the Li content (r^2 = 0.96). Mossbauer studies from the different zones within this crystal show that the Fe^(3+)/Fe(total) ratio increases continuously from the Fe-rich core to the Fe-poor near-rim zone, consistent with increasing oxygen fugacity during pegmatite pocket evolution. There is a high positive correlation between lattice parameter a (for values ≥ 15.84 A) and (Fe^(2+) + Mn^(2+)) content in tourmalines from the elbaite-schorl series (r^2 = 0.99). Values lower than 15.84 A for a are likely a consequence of greater ^([4])B contents in samples that usually have a (Fe^(2+) + Mn^(2+)) content of