Tetrahedral substitutions in tourmaline: A review
© 2018 E. Schweizerbart’sche Verlagsbuchhandlung. The Si4+ cation, typically the overwhelming occupant of the tetrahedral site of the tourmaline structure, can be partially replaced by Al3+,B3+, and Be2+Tetrahedrally coordinated Al (up to ∼0.9Al atom per formula unit, apfu) has been found in different Mg-and/or Fe2+-rich tourmalines from high-temperature aluminous lithologies as well as in Li-rich pegmatites. It is relatively common for Li-andAl-bearing tourmalines to also contain someB. While the highest boron content (∼0.8B apfu) in a natural tourmaline was found in an Al-rich tourmaline (olenite) from the Eastern Alps, Austria, much higher contents of up to ∼2.8 apfu have been reported for synthetic Al-rich tourmalines. Natural tourmalines with a higher total Al content (> 7.2 Al apfu) can also contain significantB. The highest verified beryllium content in a tourmaline is still below 100 ppm, but current data show that in pegmatitic tourmaline crystals the Be content is positively correlated with the overall Al content. Therefore Li-rich tourmalines can contain higher Be contents in pegmatites that originated from differentiated granitic magma, than in pegmatites that have evolved as granitic pegmatitic melts from the surrounding country-rocks during decompression.
Publication Source (Journal or Book title)
European Journal of Mineralogy
Ertl, A., Henry, D., & Tillmanns, E. (2018). Tetrahedral substitutions in tourmaline: A review. European Journal of Mineralogy, 30 (3), 465-470. https://doi.org/10.1127/ejm/2018/0030-2732