ALBERT

Description: Bosiite, NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is a new mineral species of the tourmaline supergroup from the Darasun gold deposit (Darasun mine), Vershino-Darasunskiy, Transbaikal Krai, Eastern-Siberian Region, Russia (52°20'24''N, 115°29'23''E). Bosiite formed as a hydrothermal phase in a gold-bearing quartz-vein spatially related to the Amudzhikan–Sretensky subvolcanic K-rich granodiorite-porphyry intrusion. Ores of this deposit are enriched in sulfides (up to 60%). Bosiite is intimately associated with other tourmalines. The first tourmaline generation is bosiite, which is followed by a second generation of oxy-dravite and a third generation of dravite. Bosiite also coexists with quartz and pyrite; further associated minerals in the vein are gangue minerals (quartz, calcite, and dolomite), sulfides (pyrite, arsenopyrite, chalcopyrite, pyrrhotite, tetrahedrite, sphalerite, and galena) and native gold. Crystals of bosiite are dark brown to black with a pale-brown streak. Bosiite is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and cleavage. It has a measured density of 3.23(3) g/cm 3 (by pycnometry) and a calculated density of 3.26(1) g/cm 3 . In plane-polarized light, it is pleochroic, O = yellow-brown, E = red-brown. Bosiite is uniaxial negative, = 1.760(5), = 1.687(5). The mineral is trigonal, space group R 3 m , a = 16.101(3), c = 7.327(2) Å, V = 1645.0(6) Å 3 . The eight strongest X-ray diffraction lines in the (calculated) powder pattern [ d in Å( I ) hkl ] are: 2.606(100)(50-1), 8.051(58)(100), 3.008(58)(3-1-2), 4.025(57)(4-20), 3.543(50)(10-2), 4.279(46) (3-11), 2.068(45)(6-1-2), 4.648(28)(300). Analysis by a combination of electron microprobe (EMPA), inductively coupled plasma mass spectrometry (ICP-MS), Mössbauer spectroscopic data and crystal-structure refinement results in the empirical structural formula: \[ \begin{array}{c}{}^{X}{\left({\mathrm{Na}}_{0.73}{\mathrm{Ca}}_{0.23}{\square }_{0.04}\right)}_{\mathrm{\Sigma }1.00}{}^{Y}{\left({\mathrm{Fe}}^{3+}{}_{1.47}{\mathrm{Mg}}_{0.80}{\mathrm{Fe}}^{2+}{}_{0.59}{\mathrm{Al}}_{0.13}{\mathrm{Ti}}^{4+}{}_{0.01}\right)}_{\mathrm{\Sigma }3.00}{}^{Z}{\left({\mathrm{Al}}_{3.23}{\mathrm{Fe}}^{3+}{}_{1.88}{\mathrm{Mg}}_{0.89}\right)}_{\mathrm{\Sigma }6.00}\\\relax {}^{T}{\left({\mathrm{Si}}_{5.92}{\mathrm{Al}}_{0.08}{\mathrm{O}}_{18}\right)}_{\mathrm{\Sigma }6.00}{\left({\mathrm{BO}}_{3}\right)}_{3}{}^{V}{\left(\mathrm{OH}\right)}_{3}{}^{W}{\left[{\mathrm{O}}_{0.85}{\left(\mathrm{OH}\right)}_{0.15}\right]}_{\mathrm{\Sigma }1.00}\end{array} \] According to the IMA-CNMNC guidelines, the dominant valence at the Y site is 3+ and the dominant cation is Fe 3+ . To accommodate the disorder and allocating cations to the Z and Y sites, the recommended procedure leads to the optimized empirical formula (based on 31 O): X (Na 0.73 Ca 0.23 0.04 ) Y (Fe 3+ 2.40 Fe 2+ 0.59 Ti 4+ 0.01 ) Z (Al 3.36 Mg 1.69 Fe 3+ 0.95 ) T (Si 5.92 Al 0.08 O 18 ) (BO 3 ) 3 V (OH) 3 W [O 0.85 (OH) 0.15 ]. Bosiite, ideally NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is related to end-member povondraite, ideally NaFe 3+ 3 (Fe 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitution Z Al 4 -〉 Z Fe 3+ 4 . Further, bosiite is related to oxy-dravite, ideally Na(Al 2 Mg)(Al 5 Mg)(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitutions [6] Fe 3+ 3 -〉 [6] Al 3 . Bosiite is named after Dr. Ferdinando Bosi, researcher at the University of Rome La Sapienza, Italy, and an expert on the crystallography and mineralogy of the tourmaline-supergroup minerals and the spinels.

Description: Arsenohopeite, ideally Zn3(AsO4)2·4H2O, is the arsenate analogue of hopeite, Zn3(PO4)2·4H2O (it is isostructural with α-hopeite). It was found as a single colourless to blue crystalline grain from the Tsumeb mine, Namibia. The holotype specimen is ~1×1×1 mm in size. Arsenohopeite is associated with tiny white fibres of an unidentified Zn- and As-bearing phase. It is orthorhombic, space group Pnma, with a = 10.804(2), b = 19.003(4), c = 5.112(1) Å, V = 1049.5(4) Å3 and Z = 4. Electron microprobe analysis yielded: ZnO 44.92, Fe2O3 0.92, MnO 0.51, MgO 0.20, CuO 0.02, As2O5 45.84 (wt.%). The empirical formula is (Zn2.80Fe0.06Mn0.04Mg0.03)Σ2.93(As1.01O4)2·4H2O, based on 12 oxygen atoms. Optically, the mineral is biaxial negative, with α = 1.598(2), β = 1.606(2), γ = 1.613(2) (white light) and 2Vcalc = 86°. It is not pleochroic or fluorescent. Arsenohopeite is translucent with a vitreous lustre. It is brittle, has an uneven fracture and (by analogy with hopeite) a cleavage that is perfect on {010}, good on {100} and poor on {001}. The calculated density is 3.420 g cm−3. The five strongest calculated powder diffraction lines are [d in Å (I)(hkl)]: 9.502 (100)(020), 2.926 (95)(241), 4.937 (50)(011), 4.110 (48)(230) and 3.567 (31)(240). The crystal structure of arsenohopeite has been solved by direct methods and refined in space group Pnma to R1 = 0.0353. Raman spectroscopy confirms the crystal-structure data and indicates the presence of weak hydrogen bonds.

Description: The crystal structure of synthetic BaMg(CO 3 ) 2 whose mineral name is norsethite was re-investigated by single-crystal X-ray diffraction. Complementary in situ high- and low-temperature studies by means of vibrational spectroscopy (Raman, IR), powder X-ray diffraction techniques and thermal analyses were performed. Diffraction images (298 K) revealed weak superstructure reflections caused by the displacement of the O atoms in the earlier considered R 3I m structure model ( a = 5.0212(9), c new = 2 c old = 33.581(6) Å, R 3I c , Z = 6, R 1 = 0.011, sin/ 〈 0.99 Å –1 ). Thermal analyses reveal decarbonatization in two decomposition steps above 750 K, and the heat-flow curves (difference scanning calorimetry) give clear evidence of a weak and reversible endothermal change at 343±1 K. This agrees with a discontinuity in the IR and single-crystal Raman spectra. The changing trend of the c/a ratio supports this discontinuity indicating a temperature-induced structural transition in the range between 343 and 373 K. As the change of the unit-cell volume is almost linear, the character of the transition is apparently second order and matches the mechanism of a subtle displacement of the oxygen atom position. The apparent instability of the R 3I c structure is also evidenced by the remarkably larger anisotropic displacement of the oxygen atom.

Description: Cairncrossite is a new phyllosilicate species found in manganese ore on dumps of the Wessels Mine, Kalahari Manganese Field, South Africa. Associated minerals are richterite, sugilite, lizardite and fibrous pectolite. It occurs as radiating platy micaceous aggregates of up to 1 cm in size. Cairncrossite is colourless, appearing white, and the crystals are translucent to transparent with a white streak and vitreous to pearly lustre. The crystals are sectile before brittle fracture, with a Mohs hardness of 3. A perfect cleavage parallel (001) is observed. The calculated density is 2.486 g cm –3 . The mineral is biaxial positive with n α = 1.518(2), n β = 1.522(2), n = 1.546(2), 2 V obs = 33.9(6)° (2 V calc = 44.97°) at 589.3 nm and 24°C. The orientation of the indicatrix is Z ^ c * = 10°. The dispersion is weak ( r 〈 v ) and no pleochroism is observed. An intense light-blue fluorescence is emitted under shortwave UV radiation. Cairncrossite is triclinic, space group P $$\overline{1}$$ , a = 9.6265(5), b = 9.6391(5), c = 15.6534(10) Å, α = 100.89(1), β = 91.27(1), = 119.73(1)°, V = 1227.08(13) Å 3 , Z = 1. The strongest lines in the Gandolfi X-ray powder-diffraction pattern [ d in Å( I )( hkl )] are 15.230 (100)(001), 8.290 (15)(1–10), 5.080(25)(003), 3.807(30)(004), and 3.045(20)(005). The chemical composition obtained by electron-microprobe analysis is Na 2 O 3.06, K 2 O 0.11, CaO 18.61, SiO 2 54.91, SrO 11.75, total 88.44 wt%. The relevant empirical formula, based on 16 Si atoms per formula unit ( apfu ) and TGA data is: Sr 1.99 K 0.02 Ca 5.81 Na 1.73 Si 16 O 55.84 H 30.33 . Taking variable sodium contents into account, the idealized structural formula is Sr 2 Ca 7–x Na 2x (Si 4 O 10 ) 4 (OH) 2 (H 2 O) 15–x with 0 ≤ x ≤ 1, and the simplified formula for sodium-rich crystals is SrCa 3 Na(Si 4 O 10 ) 2 (OH)(H 2 O) 7 with Z = 2. The structure of cairncrossite was refined on single-crystal X-ray data (Mo K α radiation) to R 1 = 0.047. Cairncrossite belongs to the gyrolite and reyerite mineral groups, it is characterized by sheets consisting of edge-sharing CaO 6 octahedra, which are corner-linked on both sides to silicate layers. These units are intercalated by layers formed by SrO 8 polyhedra, which are arranged in pairs via a common edge, and further bound to disordered NaO 6 polyhedra. A complex system of hydrogen bonds strengthens the linkage to adjacent silicate layers. Cairncrossite exhibits a two-phase endothermic weight loss of the H 2 O molecules in the range 25–400°C; however, the mineral shows a nearly complete rehydration capability up to 400°C. The new mineral is named in honour of Bruce Cairncross, Professor and Head of the Department of Geology, University of Johannesburg.

Description: Fluor-schorl, NaFe 2+ 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 F, is a new mineral species of the tourmaline supergroup from alluvial tin deposits near Steinberg, Zschorlau, Erzgebirge (Saxonian Ore Mountains), Saxony, Germany, and from pegmatites near Grasstein (area from Mittewald to Sachsenklemme), Trentino, South Tyrol, Italy. Fluor-schorl was formed as a pneumatolytic phase and in high-temperature hydrothermal veins in granitic pegmatites. Crystals are black (pale brownish to pale greyish-bluish, if 〈0.3 mm in diameter) with a bluish-white streak. Fluor-schorl is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and a poor/indistinct cleavage parallel to {0001}. It has a calculated density of ~3.23 g/cm 3 . In plane-polarized light, it is pleochroic, O = brown to grey-brown (Zschorlau), blue (Grasstein), E = pale grey-brown (Zschorlau), cream (Grasstein). Fluor-schorl is uniaxial negative, = 1.660(2)–1.661(2), = 1.636(2)–1.637(2). The mineral is rhombohedral, space group R 3 m, a = 16.005(2), c = 7.176(1) Å, V = 1591.9(4) Å 3 (Zschorlau), a = 15.995(1), c = 7.166(1) Å, V = 1587.7(9) Å 3 (Grasstein), Z = 3. The eight strongest observed X-ray diffraction lines in the powder pattern [ d in Å ( I ) hkl ] are: 2.584(100)(051), 3.469(99)(012), 2.959(83)(122), 2.044(80)(152), 4.234(40)(211), 4.005(39)(220), 6.382(37)(101), 1.454(36)(514) (Grasstein). Analyses by a combination of electron microprobe, secondary-ion mass spectrometry (SIMS), Mössbauer spectroscopic data and crystal-structure refinement result in the structural formulae X (Na 0.82 K 0.01 Ca 0.01 0.16 ) Y (Fe 2+ 2.30 Al 0.38 Mg 0.23 Li 0.03 Mn 2+ 0.02 Zn 0.01 0.03 ) 3.00 Z (Al 5.80 Fe 3+ 0.10 Ti 4+ 0.10 ) T (Si 5.81 Al 0.19 O 18 ) (BO 3 ) 3 V (OH) 3 W [F 0.66 (OH) 0.34 ] (Zschorlau) and X (Na 0.78 K 0.01 0.21 ) Y (Fe 2+ 1.89 Al 0.58 Fe 3+ 0.13 Mn 3+ 0.13 Ti 4+ 0.02 Mg 0.02 Zn 0.02 0.21 ) 3.00 Z (Al 5.74 Fe 3+ 0.26 ) T (Si 5.90 Al 0.10 O 18 ) (BO 3 ) 3 V (OH) 3 W [F 0.76 (OH) 0.24 ] (Grasstein). Several additional, newly confirmed occurrences of fluor-schorl are reported. Fluor-schorl, ideally NaFe 2+ 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 F, is related to end-member schorl by the substution F -〉 (OH). The chemical compositions and refined crystal structures of several schorl samples from cotype localities for schorl (alluvial tin deposits and tin mines in the Erzgebirge, including Zschorlau) are also reported. The unit-cell parameters of schorl from these localities are slightly variable, a = 15.98–15.99, c = 7.15–7.16 Å, corresponding to structural formulae ranging from ~ X (Na 0.5 0.5 ) Y (Fe 2+ 1.8 Al 0.9 Mg 0.2 0.1 ) Z (Al 5.8 Fe 3+ 0.1 Ti 4+ 0.1 ) T (Si 5.7 Al 0.3 O 18 ) (BO 3 ) 3 V (OH) 3 W [(OH) 0.9 F 0.1 ] to ~ X (Na 0.7 0.3 ) Y (Fe 2+ 2.1 Al 0.7 Mg 0.1 0.1 ) Z (Al 5.9 Fe 3+ 0.1 ) T (Si 5.8 Al 0.2 O 18 ) (BO 3 ) 3 V (OH) 3 W [(OH) 0.6 F 0.4 ]. The investigated tourmalines from the Erzgebirge show that there exists a complete fluor-schorl–schorl solid-solution series. For all studied tourmaline samples, a distinct inverse correlation was observed between the X –O2 distance (which reflects the mean ionic radius of the X -site occupants) and the F content ( r 2 = 0.92). A strong positive correlation was found to exist between the F content and the 〈 Y –O〉 distance ( r 2 = 0.93). This correlation indicates that Fe 2+ -rich tourmalines from the investigated localities clearly tend to have a F-rich or F-dominant composition. A further strong positive correlation ( r 2 = 0.82) exists between the refined F content and the Y–W (F,OH) distance, and the latter may be used to quickly estimate the F content.

Description: The crystal structures of the secondary ferric iron minerals kamarizaite, Fe 3 3+ (AsO 4 ) 2 (OH) 3 · 3H 2 O, and tinticite, Fe 3 3+ (PO 4 ) 2 (OH) 3 · 3H 2 O, for which highly contradictory data on crystal symmetry were reported, were studied by a combination of single-crystal X-ray diffraction and Rietveld refinement (supplemented by chemical analyses and thermogravimetry), using type material of both species and additional samples from several other localities, including the type localities. The previously unknown crystal structure of kamarizaite was determined from single-crystal intensity data (Mo K α, 293 K, R ( F ) = 2.91 %; all H atoms detected) using a sample from the Le Mazet vein, Échassières, Auvergne, France. The mineral is triclinic, space group $$P\overline{1}$$ (no. 2), with a = 7.671(2), b = 8.040(2), c = 10.180(2) Å, α = 68.31(3), β = 75.35(3), = 63.52(3)°, V = 519.3(2) Å 3 , Z = 2. Rietveld analyses of fine-grained kamarizaite collected underground at two different spots in Lavrion, Greece (Hilarion and Jean Baptiste areas) confirmed the structure model. Rietveld analyses of fine-grained tinticite from Tintic, Utah (USA), Bruguers (Spain) and Weckersdorf (Germany) demonstrate that kamarizaite and tinticite are triclinic and isotypic. A previously published structure model for tinticite, as well as the originally reported orthorhombic symmetry for kamarizaite, are shown to be incorrect. Refined unit-cell parameters of a cotype tinticite specimen from Tintic are: a = 7.647(1), b = 7.958(1), c = 9.987(1) Å, α = 67.90(1), β = 76.10(1), = 64.10(1)°, V = 504.4(2) Å 3 . Bruguers and Weckersdorf tinticite have very similar parameters. The common atomic arrangement is characterised by three unique, octahedrally coordinated Fe sites (on which Fe may be partially replaced by minor Al), two unique tetrahedrally coordinated T (As or P) sites, eight O, three O h , three O w and nine H sites. The topology features zig-zag chains along $$\left[\overline{1}10\right]$$ of dimers built of two edge-sharing FeO 6 octahedra corner-linked by a third FeO 6 octahedron. The chains are corner-linked by the T O 4 tetrahedra thus establishing a mixed octahedral-tetrahedral framework with a T :Fe ratio of 0.67, a pronounced layered arrangement parallel to (001) and narrow channels along [010]. Medium-strong to weak hydrogen-bonds provide additional strengthening of the structure. The topology is closely related to that of the recently described, triclinic aluminium phosphate afmite.

Description: Crystal structures, chemical (including light elements) and spectral data (optical and Mössbauer spectroscopies) were used to characterize coloured (brown, pink, green) tourmalines from three granitic pegmatites from the Moldanubian nappes (Königsalm, Maigen and Blocherleitengraben; Lower Austria). The tourmalines can be classified as fluor-schorl, schorl, foitite, magnesiofoitite, olenite and "fluor-elbaite" with varying Li contents, up to ~1.2 wt% Li 2 O. Coexisting minerals are quartz, plagioclase (up to An 7 ), microcline, garnet (spessartine-almandine), muscovite, biotite (annite), very rare lepidolite, apatite, monazite-(Ce), xenotime-(Y), allanite-(Ce) and zircon. The chemical composition of the Fe 2+ -rich tourmaline samples (up to ~1.0 wt% TiO 2 ) varies from fluor-schorl, with a = 15.987(2), c = 7.163(2) Å to X ( 0.63 Na 0.37 ) Y (Fe 2+ 1.12 Al 1.09 Mg 0.56 Mn 2+ 0.08 Fe 3+ 0.07 Li 0.02 Ti 4+ 0.01 Zn 0.01 0.04 ) Z (Al 5.74 Mg 0.26 ) (BO 3 ) 3 [Si 5.96 Al 0.04 O 18 ] V (OH) 3 W [(OH) 0.95 F 0.05 ], strongly dichroic (pink and blue) foitite, with a = 15.9537(2), c = 7.1448(4) Å, to X ( 0.51 Na 0.49 ) Y (Fe 2+ 0.97 Al 0.93 Mg 0.75 Fe 3+ 0.23 Mn 2+ 0.04 Li 0.01 Ti 4+ 0.01 0.06 ) Z (Al 5.72 Mg 0.28 ) (BO 3 ) 3 [Si 5.95 Al 0.05 O 18 ] V (OH) 3 W [(OH) 0.91 O 0.06 F 0.03 ], magnesiofoitite, with a = 15.9476(4), c = 7.1578(4) Å. The chemical composition of the Al- and Li-rich and Mn 2+ -bearing (up to ~5.7 wt% MnO) samples varies from X (Na 0.84 Ca 0.02 0.14 ) Y (Al 1.35 Li 0.78 Mn 2+ 0.65 Ti 4+ 0.01 0.21 ) Z Al 6 (BO 3 ) 3 [Si 5.92 Al 0.04 B 0.04 O 18 ] V (OH) 3 W [F 0.81 (OH) 0.19 ], "fluor-elbaite" with a = 15.8887(3), c = 7.1202(3) Å, to X (Na 0.76 Ca 0.12 0.12 ) Y (Al 1.52 Li 0.69 Mn 2+ 0.43 Fe 2+ 0.09 0.27 ) Z Al 6 (BO 3 ) 3 [Si 5.71 B 0.29 O 18 ] V (OH) 3 W [F 0.69 (OH) 0.31 ], B-rich "fluorelbaite", with a = 15.8430(3), c = 7.1051(3) Å. A positive correlation between the 〈 T -O〉 and 〈 Z -O〉 bond lengths in tourmalines where the Z site is only occupied by Al ( R 2 = 0.617) is useful to correct the 〈 Z -O〉 bond length for the inductive effect of the varying 〈 T -O〉 bond length. This is important for producing accurate assignments for the different 6-coordinated sites in tourmaline. On the basis of Sm-Nd (garnet, monazite), U-Th-Pb, and U-Pb ages (monazite), the pegmatites crystallised during the Variscan tectonometamorphic event in the Visean (339 ± 4 Ma Maigen, 332 ± 3 Ma Königsalm). These ages are in the range of the earliest intrusions of the South Bohemian pluton (Rastenberg type durbachites). However, on the basis of the spatial relationship of the pegmatites and the Rastenberg type intrusions, a linkage of the intrusive body and the pegmatites is unlikely. Alternatively, the pegmatites may have evolved as granitic pegmatitic melts during decompression from the surrounding country rocks in the frame of exhumation of the Moldanubian nappes after the peak of the Variscan metamorphism.

Description: Fe 2+ - and Mn 2+ -rich tourmalines were used to test whether Fe 2+ and Mn 2+ substitute on the Z site of tourmaline to a detectable degree. Fe-rich tourmaline from a pegmatite from Lower Austria was characterized by crystal-structure refinement, chemical analyses, and Mössbauer and optical spectroscopy. The sample has large amounts of Fe 2+ (~2.3 apfu), and substantial amounts of Fe 3+ (~1.0 apfu). On basis of the collected data, the structural refinement and the spectroscopic data, an initial formula was determined by assigning the entire amount of Fe 3+ (no delocalized electrons) and Ti 4+ to the Z site and the amount of Fe 2+ and Fe 3+ from delocalized electrons to the Y-Z ED doublet (delocalized electrons between Y-Z and Y-Y ): X (Na 0.9 Ca 0.1 ) Y (Fe 2+ 2.0 Al 0.4 Mn 2+ 0.3 Fe 3+ 0.2 ) Z (Al 4.8 Fe 3+ 0.8 Fe 2+ 0.2 Ti 4+ 0.1 ) T (Si 5.9 Al 0.1 )O 18 (BO 3 ) 3 V (OH) 3 W [O 0.5 F 0.3 (OH) 0.2 ] with a = 16.039(1) and c = 7.254(1) Å. This formula is consistent with lack of Fe 2+ at the Z site, apart from that occupancy connected with delocalization of a hopping electron. The formula was further modified by considering two ED doublets to yield: X (Na 0.9 Ca 0.1 ) Y (Fe 2+ 1.8 Al 0.5 Mn 2+ 0.3 Fe 3+ 0.3 ) Z (Al 4.8 Fe 3+ 0.7 Fe 2+ 0.4 Ti 4+ 0.1 ) T (Si 5.9 Al 0.1 )O 18 (BO 3 ) 3 V (OH) 3 W [O 0.5 F 0.3 (OH) 0.2 ]. This formula requires some Fe 2+ (~0.3 apfu) at the Z site, apart from that connected with delocalization of a hopping electron. Optical spectra were recorded from this sample as well as from two other Fe 2+ -rich tourmalines to determine if there is any evidence for Fe 2+ at Y and Z sites. If Fe 2+ were to occupy two different 6-coordinated sites in significant amounts and if these polyhedra have different geometries or metal-oxygen distances, bands from each site should be observed. However, even in high-quality spectra we see no evidence for such a doubling of the bands. We conclude that there is no ultimate proof for Fe 2+ at the Z site, apart from that occupancy connected with delocalization of hopping electrons involving Fe cations at the Y and Z sites. A very Mn-rich tourmaline from a pegmatite on Elba Island, Italy, was characterized by crystal-structure determination, chemical analyses, and optical spectroscopy. The optimized structural formula is X (Na 0.6 0.4 ) Y (Mn 2+ 1.3 Al 1.2 Li 0.5 ) Z Al 6 T Si 6 O 18 (BO 3 ) 3 V (OH) 3 W [F 0.5 O 0.5 ], with a = 15.951(2) and c = 7.138(1) Å. Within a 3 error there is no evidence for Mn occupancy at the Z site by refinement of Al Mn, and, thus, no final proof for Mn 2+ at the Z site, either. Oxidation of these tourmalines at 700–750 °C and 1 bar for 10–72 h converted Fe 2+ to Fe 3+ and Mn 2+ to Mn 3+ with concomitant exchange with Al of the Z site. The refined Z Fe content in the Fe-rich tourmaline increased by ~40% relative to its initial occupancy. The refined Y Fe content was smaller and the 〈 Y -O〉 distance was significantly reduced relative to the unoxidized sample. A similar effect was observed for the oxidized Mn 2+ -rich tourmaline. Simultaneously, H and F were expelled from both samples as indicated by structural refinements, and H expulsion was indicated by infrared spectroscopy. The final species after oxidizing the Fe 2+ -rich tourmaline is buergerite. Its color had changed from blackish to brown-red. After oxidizing the Mn 2+ -rich tourmaline, the previously dark yellow sample was very dark brown-red, as expected for the oxidation of Mn 2+ to Mn 3+ . The unit-cell parameter a decreased during oxidation whereas the c parameter showed a slight increase.