Publication details
Fluor-rossmanite, □(Al2Li)Al6(Si6O18)(BO3)3(OH)3F, a new tourmaline supergroup mineral from Malkhan pegmatite field, Western Siberia, Russia
| Authors | |
|---|---|
| Year of publication | 2024 |
| Type | Article in Periodical |
| Magazine / Source | Mineralogical Magazine |
| MU Faculty or unit | |
| Citation | |
| web | https://doi.org/10.1180/mgm.2024.34 |
| Doi | https://doi.org/10.1180/mgm.2024.34 |
| Keywords | fluor-rossmanite; new mineral species; crystal structure refinement; electron microprobe; infrared spectroscopy; Raman spectroscopy; tourmaline supergroup; Krutaya pegmatite; Malkhan pegmatite field |
| Description | Fluor-rossmanite, ideally ?(Al2Li)Al6(Si6O18)(BO3)3(OH)3F, is a new mineral of the tourmaline supergroup, found at the Krutaya pegmatite, Malkhan pegmatite field, Zabaykalskiy Krai, Western Siberia, Russia. It forms an intermediate zone up to 3 mm thick in a chemically heterogeneous, concentrically zoned, polychrome tourmaline crystal 3 × 2 cm in size. The new mineral is light pink, transparent with a white streak and a vitreous lustre. It is brittle, with conchoidal fracture. The Mohs hardness is 7. The Dmeas = 3.07(2) g cm–3 and Dcalc = 3.071 g cm–3. Optically, fluor-rossmanite is non-pleochroic, uniaxial (–), ? = 1.647(2) and ? = 1.628(2) (589 nm). The empirical formula calculated on the basis of 31 anions (O+OH+F) is: X(?0.46Na0.32Ca0.20Pb0.02)?1.00 Y(Al1.84Li1.05Mn0.05Fe2+0.02Ti0.02Cr0.01)?2.99 ZAl6.00 T(Si5.79Al0.21)?6.00B2.99O27 V(OH)3 W[F0.44(OH)0.20O0.36]?1.00. Fluor-rossmanite is trigonal, R3m; the unit-cell parameters are: a = 15.7951(3), c = 7.08646(17) A, V = 1531.11(7) A3 and Z = 3. The crystal structure is refined from single-crystal X-ray diffraction data [R = 0.0211 for 1178 unique reflections with I > 2?(I)]. The new mineral is a ‘fluor-’ species belonging to the X-vacant group of the tourmaline supergroup. The closest end-member compositions of valid tourmaline species are those of rossmanite and fluor-elbaite, to which fluor-rossmanite is related by the substitutions WF– - WOH– and X2? + YAl3+ - X2Na+ + YLi+, respectively. |
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