Crystal-chemical characterization of tourmalines from the English Lake District: Electron-microprobe analyses and Mössbauer spectroscopy

Mushroom elbaite from the Kat Chay mine, Momeik, near Mogok, Myanmar: I. Crystal chemistry by SREF, EMPA, MAS NMR and Mössbauer spectroscopy

“…In contrast to other minerals, where Fe 2+ ÀFe 3+ intervalence charge-transfer leads to a new absorption band in the visible spectrum, in tourmalines the Fe 2+ optical absorption band may be drastically intensified by the Fe 2+ ÀFe 3+ transition without the presence of any additional bands (Smith, 1978a,b;Mattson and Rossman, 1987). It has been shown that Mössbauer spectroscopy is sensitive to Fe 2+ and Fe 3+ in different short-range arrangements in tourmaline (Dyar et al, 1998) and can identify the presence of Fe 2+ ÀFe 3+ clusters where there is electron delocalization (Hawthorne, 1988;Ferrow, 1994;Dyar et al, 1998;De Oliveira et al, 2002;Eeckhout et al, 2004). [4] B in SHM and SHP mushroom tourmaline crystals; the circles represent the amounts of [4] B derived from the formula-unit calculation; the line is drawn through the point <SiÀO> = 1.620 Å and projects to a <BÀO> distance of 1.475 Å , the grand < [4] BÀO> distance for borate minerals given by Hawthorne et al (1996).…”