|The type sample of alumino-oxy-rossmanite|
Alumino-oxy-rossmanite (IMA 2020-008) was found northeast of Eibenstein an der Thaya in a pegmatite where only a marble quarry now remains. This locality is about a km away from an olenite pegmatite that was described in Ertl et al. (2003). Only one crystal of alumino-oxy-rossmanite from this locality is known to exist. It was collected after the pegmatite was mostly mined out. The crystal is in a private collection in Europe and is about 5 mm diameter. The crystal grades from green into red and pink and has a thin dark outer zone visible in the image above. A few fragments less than 1 mm in diameter were removed for detailed scientific study. The chemical analyses obtained as part of this study led to the identification of a hydroxy-deficient, aluminum-rich mineral related to rossmanite. This has been approved as a new mineral species named alumino-oxy-rossmanite in the tourmaline family of minerals.
(0.53Na0.46Ca0.01) (Al2.37Mn0.25Li0.33Fe0.04Ti0.01) Al6 (BO3)3 [Si5.47Al0.28B0.25O18] [(OH)2.85 O0.15] (O0.86OH0.10F0.04)
The aluminum content in the Y-site exceeds the amount of the ideal rossmanite composition (LiAl2) and moves the composition towards and beyond the direction of ideal "oxy-rossmanite", Li0.5Al2.5. The mineral was first given the temporary name "oxy-rossmanite" in 2005, but the name alumino-oxy-rossmanite was finally adopted as the official species name approved by the IMA in 2020 (Ertl et al., 2020).
Ertl A, Rossman GR, Hughes JM, Prowatke S, Ludwig T (2005) Mn-bearing "oxy-rossmanite" with tetrahedrally-coordinated Al and B from Austria: structure, chemistry, and infrared and optical spectroscopic study. American Mineralogist 90, 481-487.
Ertl A, Hughes JM, Prowatke S, Rossman GR, London D, Fritz EA (2003) Mn-rich tourmaline from Austria: structure, chemistry, optical spectra, and relations to synthetic solid solutions. American Mineralogist 88, 1369-1376.
Ertl A, Hughes JM, Prowatke S, Ludwig T, Lengauer CL, Meyer HP (2020) Alumino- oxy-rossmanite, IMA 2020-008b, in: CNMNC Newsletter 58, Eur. J. Mineral., 32, https://doi.org/10.5194/ejm-32-645-2020.