Andreas Ertl

• Dr.
• Project Manager at Naturhistorisches Museum Wien

Almandine-spessartine garnet from the Moldanubian Zone in the Bohemian Massif (Austria) records microstructural and compositional features of crystal growth imprinted during the transition from pegmatoid magmatic to subsolidus state. Directed garnet growth results in asymmetric compositional, morphological and microstructural zoning. In addition, t...

Tourmaline has two different [6]-coordinated sites, the Y site and the Z site. Vacancies were reported from both sites. Based on high-quality chemical and single-crystal structural data it usually needs increasing proportions of short-range order configurations Na(Al2□)Al6(BO3)3[Si6O18]V(OH)3W(OH) or Na(Al2□)Al6(BO3)3[Si6O18]V(OH)3WF in order to pr...

Tourmaline has two different [6]-coordinated sites, the Y site and the Z site. Vacancies were reported from both sites. Based on high-quality chemical and single-crystal structural data it always needs increasing proportions or short-range order configurations Na(Al2⊏)Al6(BO3)3[Si6O18]V(OH)3W(OH) or Na(Al2⊏)Al6(BO3)3[Si6O18]V(OH)3WF in order to pro...

Tourmaline Mica Tourmaline-bearing quartzite Metamorphic conditions

Six Al- and Li-bearing tourmaline crystals from pegmatites were structurally and chemically characterized. These samples can be assigned to elbaite, fluor-elbaite and rossmanite. Quantitative analyses of light elements such as Li, B and H are not always easily accessible. Therefore a method for the calculation of Li and OH would be of a general int...

Alumino-oxy-rossmanite, ideally ☐Al3Al6(Si5AlO18)(BO3)3(OH)3O, is here described as a new member of the tourmaline supergroup. It is an early magmatic Al-rich oxy-tourmaline from a small pegmatitic body embedded in amphibolite and biotite-rich paragneiss. This new pink tourmaline was found in a Moldanubian pegmatite (of the Drosendorf Unit) that oc...

Zinc-rich fluor-elbaite from Piława Górna, Poland, was studied by electron microprobe (EPMA), single-crystal X-ray diffraction (SREF), and Raman spectroscopy (RS) to check the possibility of the application of RS to draw crystal-chemical conclusions for Al-rich and Li-bearing tourmalines on basis of the O–H stretching vibrations in the spectral ran...

Copper- and Mn-bearing elbaitic tourmaline (“Paraíba tourmaline”) sometimes contains significant amounts of Pb and Bi. Their position in the tourmaline crystal structure was studied with correlation analysis and bond valence calculations. Correlations between the F content and the X-site charge allow predicting the X-site occupancy. Three sets of t...

A detailed investigation was conducted on high-pressure (~1.4 GPa) tourmaline from an Eoalpine mafic eclogite, which occurs in the Kreuzeck Mountains, Eastern Alps, Austria. Tourmaline from this locality contains the highest amount of Sr²⁺ (up to 0.68 wt% SrO) known to date. The space group is R3m with unit-cell parameters a = 15.944(1), c = 7.202(...

In the Eastern Alps (Central Europe), about two dozen spodumene pegmatite bodies extend heterogeneously over the Austroalpine Unit. They are spatially associated with leucogranites and simple pegmatites formed during the Permian extensional event. The pegmatites and leucogranites were overprinted during the Alpine orogeny with different intensities...

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 ∼0.9[4]Al 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-r...

Yellowish dravitic tourmaline (dominated by the oxy-dravite component) associated with secondary fluor-dravite/fluor-schorl and dravite/schorl tourmalines was found in a quartz vein cropping out in the eastern part of the Karkonosze Mountains range, SW Poland. The crystal structure of this tourmaline was refined to an R1 value of 1.85% based on sin...

Red beryl from Utah is chemically homogeneous and contains only Fe < 0.163, Mn < 0.018, and Mg < 0.016 apfu. Channel sites contain only up to Cs 0.011, K 0.009, Rb 0.004, and Na 0.004 apfu. This suggests only very slight tetrahedral (Cs,K,Rb)Li□-1Be-1 substitution, octahedral Na(Fe²⁺,Mg)□-1Al-1 substitution can be excluded. Fe and Mn are trivalent...

Lithium is an important component of some tourmalines, especially in chemically evolved granites and pegmatites. All attempts at synthesizing Li-rich tourmaline have so far been unsuccessful. Here we describe the first synthesis of rossmanitic tourmaline at 4 GPa and 700 °C in the system Li2O–Al2O3–SiO2–B2O3–H2O (LASBH) from seed-free solid startin...

Bosiite, NaFe3+3(Al4Mg2)(Si6O18)(BO3)3(OH)3O, 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–...

Fluor-schorl, NaFe^(2+) _3Al_6Si_6O_(18)(BO_3)_3(OH)_3F, 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...

Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounce...

The crystal structures of synthetic K-dravite [XKYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], dravite [XNaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)], oxy-uvite [XCaYMg 3 Z Al 6 T Si6O18(BO3) 3 V (OH) 3 W O], and magnesio-foitite [X☐Y(Mg2Al)ZAl 6 T Si6O18(BO3) 3 V (OH) 3 W (OH)] are investigated by polarized Raman spectroscopy, single-crystal s...

Olenitic tourmaline with high amounts of tetrahedral B (up to 2.53 [4]B pfu) has been synthesized in a piston-cylinder press at 4.0 GPa, 700 °C, and a run duration of 9 days. Crystals are large enough (up to 30 × 150 μm) to allow for reliable and spatially resolved quantification of B by electron microprobe analysis (EMPA), single-crystal X-ray dif...

Copper-bearing tourmalines are highly prized for their vivid coloration. We analysed the major and trace elements of some gem-quality Cu-bearing tourmalines (e.g. blue, greenish blue, yellowish green, green, violet and pink) from Brazil, Mozambique and Nigeria. Most of them contained significant amounts of Cu, Mn or a combination of both elements....

A synthetic Cu-rich tourmaline crystal (Lebedev et al. 1988) consists of three different zones. Each zone was characterized by EMPA, SIMS, and single-crystal structure refinement (SREF). The first zone (which crystallized directly on the seed crystal) has the formula ~X(Na0.8□0.2) Y(Al2.0Cu0.9□0.1) ZAl6 T(Si5.1Al0.9)O18 (BO3)3 V(OH)3 W[O0.7F0.2(OH)...

Distinctly chemically zoned tourmaline was found in a quartz vein near Tisovec, Slovak Ore Mountains, Slovakia. The tourmaline forms radial aggregates of light grey to green thin prismatic to acicular crystals growing in cracks in the host rock. The root zone of the aggregates has dravitic to oxy-dravitic compositions, shifting to magnesio-foitite...

Darrellhenryite, Na(LiAl2)Al-6(BO3)(3)Si6O8(OH)(3)O, a new member of the tourmaline supergroup (related to the alkali-subgroup 4), is a new Li-bearing tourmaline species, which is closely related to elbaite through the substitution (Al0.5O1Li-0.5W)-Al-Y-O-W-Li-Y(OH)(-1). It occurs in a complex (Li-bearing) petalite-subtype pegmatite with common lep...

As part of a wider study on the crystal chemistry of tourmaline-group members from Norway, occurrences of luinaite-(OH), fluor-schorl and other members have been reported (Kolitsch et al. 2011). The present contribution presents further results based on characterisations of different samples from various pegmatite localities in the Langesundsfjord...

A detailed study of the chemical composition and substitutions in calcium tourmalines from a scapolite-bearing rare-metal pegmatite vein from the Sol’bel’der River basin has shown that their species attribution is determined by occupancy of octahedral site Y. The composition of the yellow tourmaline most abundant in the central part of the pegmatit...

Green to grayish green tourmaline crystals (up to 10 cm across), with distinct optical zoning, occurs with quartz, blocky albite and muscovite in the Forshammar granitic pegmatite, central Bergslagen province, Sweden. Tourmaline contains inclusions of zircon and xenotime-(Y), and it is cut by veinlets of muscovite and hydroxylbastnäsite-(Ce). Micro...

Synthetic Al- and B-rich tourmaline crystals described by London (2011) were characterized further by SIMS and new EMP analyses. These tourmalines are the first synthetic B-rich olenites characterized by single-crystal X-ray diffraction, because they are significantly larger than synthetic samples produced in the past. The average final formulas ar...

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+...

Crystal structures, chemical (including light elements) and spectral data (optical and Mossbauer spectroscopies) were used to characterize coloured (brown, pink, green) tourmalines from three granitic pegmatites from the Moldanubian nappes (Konigsalm, Maigen and Blocherleitengraben; Lower Austria). The tourmalines can be classified as fluor-schorl,...

The [9]-coordinated X site in tourmaline is usually occupied by Na, Ca, K, or is vacant. In contrast to earlier statements in the literature our recent evaluation of 81 tourmaline samples with Al on the Z site has clearly shown that the < X-O > distance, as could have been expected, is positively correlated to the average effective ionic radius of...

Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounce...

Due to the extraordinary geotectonic location of the Aegean above an active subduction zone and an exceptional high seismicity, this area and especially the Cyclades have been in the focus of structural investigations for several decades. The present deformation is the result of ongoing plate tectonic movements in this area since at least the Mioce...

A nomenclature for tourmaline-supergroup minerals is based on chemical systematics using the generalized tourmaline structural formula: XY 3 Z 6 (T 6 O 18)(BO 3) 3 V 3 W, where the most common ions (or vacancy) at each site are X = Na 1+ , Ca 2+ , K 1+ , and vacancy; Y = Fe 2+ , Mg 2+ , Mn 2+ , Al 3+ , Li 1+ , Fe 3+ , and Cr 3+ ; Z = Al 3+ , Fe 3+...

A nomenclature for tourmaline-supergroup minerals is based on chemical systematics using the generalized tourmaline structural formula: XY(3)Z(6)(T(6)O(18))(BO(3))(3)V(3)W, where the most common ions (or vacancy) at each site are X = Na(1+), Ca(2+), K(1+), and vacancy; Y = Fe(2+), Mg(2+), Mn(2+), Al(3+), Li(1+), Fe(3+), and Cr(3+); Z = Al(3+), Fe(3...

A nomenclature for tourmaline-supergroup minerals is based on chemical systematics using the generalized tourmaline structural formula: XY 3 Z 6 (T 6 O 18)(BO 3) 3 V 3 W, where the most common ions (or vacancy) at each site are X = Na 1+ , Ca 2+ , K 1+ , and vacancy; Y = Fe 2+ , Mg 2+ , Mn 2+ , Al 3+ , Li 1+ , Fe 3+ , and Cr 3+ ; Z = Al 3+ , Fe 3+...

Synkinematic tourmaline and quartz growth on slickensides of brittle-ductile normal fault planes was studied by electron-microprobe analysis and X-ray crystallographic methods. The faults show top-to-the-southwest sense of shear and cross-cut mylonitic gneisses of the Cycladic Blueschist Unit on Despotiko Island, located southwest of Antiparos, in...

Although putatively possessing hexagonal R3m symmetry, reports of optically anomalous tourmaline are common, and recently an occurrence of triclinic tourmaline was reported with dissymmetrization that resulted from non-equivalency of the occupants of the Y sites. We report the atomic arrangement of Ni-bearing dravite from the Berezovskoe gold depos...

Pale-blue to pale-green tourmalines from the contact zone of Permian pegmatites to mica schists and marbles from different localities of the Austroalpine basement units (Rappold Complex) in Styria, Austria, are characterized. All these Mg-rich tourmalines have small but significant Li contents, up to 0.29wt% Li2O, and can be characterized as dravit...

Chemical, structural, infrared, optical, and Mössbauer spectroscopic data were obtained on tourmalines from gem pockets in the Himalaya mine, San Diego County, California, including a strongly color-zoned crystal. Calcium and Li abundances increase from core to rim, whereas Mn^(2+) and F increase, reach a maximum, and then decrease. Upon initiation...

Tourmaline grains extrcted from rocks within three ultrahigh-pressure (UHP) metamorphic localities have been subjected to a structurally and chemically detailed analysis to test for any systematic behavior related to temperature and pressure. Dravite from Parigi, Dora Maira, Western Alps (peak P-T conditions ~3.7 GPa, 750 °C), has a structural form...

The “watermelon” tourmaline from the Paprok mine (Nuristan, Afghanistan) shows different tourmaline components. Four zones differ widely what is reflected by different chemistry and various colours (pink core and green rim). All zones show a relatively low Mn content (∼0.05 apfu) but different Fe contents. While Fe is in the (pink) core at the dete...

Single-crystal structure and chemical (EMPA, SIMS, TGA) data were obtained from three pale coloured to colourless Al- and Li-rich tourmaline crystals from a pegmatite from Wolkenburg near Limbach-Oberfrohna, Saxony, Germany. Tourmaline samples of the "fluor-elbaite"-rossmanite solid solution series were chemically (including the light elements) and...

An Al-rich tourmaline from the Sahatany Pegmatite Field at Manjaka, Sahatany Valley, Madagascar, was structurally and chemically characterized. The combination of chemical and structural data yields an optimized formula of X (Na0.53Ca0.09□0.38) Y (Al2.00Li0.90Mn²⁺0.09Fe²⁺0.01) Z Al6 (BO3)3T [Si5.61B0.39]O18V (OH)3W [(OH)0.6O0.4], with a = 15.777(1)...

Pertlikite, a new member of the voltaite group, is the tetragonal Mg-dominant analogue of the isometric phases voltaite and zincovoltaite. At its type locality, Madeni Zakh, Iran, the mineral occurs in a pyrite-bearing trachytic eruptive rock, and probably formed after the decomposition of pyrite. Pertlikite forms single crystals up to I cm; the ph...

An optical absorption spectrum, structural and chemical data of green V- and Cr-bearing tourmaline from the graphite deposit at Weinberg Mountain, west of the village of Amstall, Lower Austria, were obtained. To address the role of V and Cr in the spectrum of tourmaline, examination of additional samples of V- and Cr-containing tourmalines was cond...

Rietveld refinement using synchrotron powder X-ray diffraction data of the ranciéite, Ca0.19K0.01(Mn4+0.91◻0.09)O2⋅0.63H2O, crystal structure reveals significant differences from that reported previously. The interlayer H2O molecules occupy sites halfway between the Mn,O octahedral sheets. The Mn sites in the octahedral sheets have 10% vacancies, a...

So-called "mushroom" tourmaline, a botryoidal aggregate of pale pink tourmaline crystals, occurs in the Palelni mine, Khetchel village, Molo quarter, Momeik Township, northeast of Mogok, Mandalay Division, Shan State, Myanmar. It has been characterized by crystal-structure determination, electron-microprobe analysis (EMPA), secondary-ion mass spect...

{{Four colorless tourmalines of the liddicoatite-elbaite series from pegmatites from Anjanabonoina, Madagascar, have been characterized by crystal-structure determination and by chemical analyses. Optimized formulae range from (x)(Ca0.57Na0.29 rectangle(0.14)) (Y)(Al1.41Li1.33Mn0.072+rectangle(0.19)) Al-z(6)T (Si5.86B0.14)O-18(BO3)(3) v(OH)(3.00) W...

The F-analogue of schorl has been identified in samples from a pegmatite at Grasstein, Trentino-South Tyrol, Italy. The crystal chemistry of this tourmaline has been characterized by a combination of single-crystal structure refinement, chemical anal ysis, and Mossbauer spectroscopy, yielding the structural formula (X)(Na0.78K0.01 square(0.21)) (Y)...

Ag-rich tourmaline crystals were synthesized at 750 °C, 200 MPa H2O, and fO2 = log (NNO) – 0.5, starting with an oxide mix of dravite composition to which various reagents, including AgF and AgCl, were added. Tourmaline containing up to 7.65 wt% Ag2O was synthesized, and this is the first time a tourmaline is described that contains significant amo...

The pale blue rim of olenite on a black crystal of olenite-schorl tourmaline from an abyssal pegmatite at the locality Kuklik, near Kutna Hora, Czech Republic, has been chemically and structurally characterized. The optimized formula, calculated using chemical and structural data, is {sup X}(Na{sub 0.54}Ca{sub 0.14}K{sub 0.01}{D'Alembertian}{sub 0....

2006) — Clinopyroxene from an alkali pyroxenite xenolith, Louèná-Oberwiesenthal Volcanic Centre, Bohemian Massif: crystal chemistry and structure. Geol. Quart., 50 (2): 257–264. Warszawa. Alkali pyroxenite (and ijolite) xenoliths occur in the Tertiary Louèná-Oberwiesenthal Volcanic Centre associated with the Ohøe/Eger Rift. The alkali pyroxenite xe...

Rancieite from Friesach, Carinthia, Austria, is described from an oxidation zone of a small (Mn-bearing) siderite deposit. This mineral is associated with "buserite-(Ca)", hollandite, braunite, romanechite, todorokite, cryptomelane, pyrolusite, manganite, nsutite, goethite, lepidocrocite, and calcite. Rancieite rarely forms small purple-silver grey...

For dumortierite from Gfohl Lower Austria, crystal structure refinement in combination with chemical analyses gives the optimized formula (Al(0.78)square(0.12)Mg(0.09)Ti(0.01)) (Al(5.70)square(0.20)Ti(0.06)Fe(0.04)) (Si2.85Al0.15) B O-16 [O-1.17(OH)(0.8) F-0.02], with a = 4.6900(3), b = 11.7875(6), c = 20.1823(11) angstrom. For dumortierite from We...

Pink, Mn-bearing “oxy-rossmanite” from a pegmatite in a quarry near Eibenstein an der Thaya, Lower Austria, has been characterized by crystal structure determination, chemical analyses (EMPA, SIMS), and optical absorption and infrared spectroscopy. Crystal structure refinements in combination with the chemical analyses give the optimized formulae ^...

{{Metamorphic Fe-bearing dravite from a glaucophane schist from Syros, Greece, associated with omphacite, has been characterized by chemical analyses (EMPA, SIMS, Mossbauer study) and by crystal structure determination. The optimized formula, calculated using chemical and structural data (including from Mossbauer spectroscopy) is (X)(Na(0.96)Ca(0.0...

A sample of dark green Fe-rich (~7 wt% FeOtotal) and Mn-bearing olenite from a beryl-bearing granitic pegmatite near Eibenstein, Lower Austria, was chemically and structurally characterized. Electron-microprobe analyses clearly indicate a defi- ciency in Si. Tetrahedrally coordinated B was not found by chemical analysis (2.98 apfu B by SIMS analysi...

Yellow-brown to pink Mn-rich tourmalines with MnO contents in the range 8-9 wt% MnO (∼0.1 wt% FeO) from a recently discovered locality in Austria, near Eibenstein an der Thaya (Lower Austria), have been characterized by crystal structure determination, by chemical analyses (EMPA, SIMS), and by optical absorption spectroscopy. Qualitatively, the opt...

A sample of dark green Fe-rich (∼7 wt% FeOtotal) and Mn-bearing olenite from a beryl-bearing granitic pegmatite near Eibenstein, Lower Austria, was chemically and structurally characterized. Electron-microprobe analyses clearly indicate a deficiency in Si. Tetrahedrally coordinated B was not found by chemical analysis (2.98 apfu B by SIMS analysis)...

Mn-rich tourmaline (up to 8.89 wt% MnO) and fluorapatite (up to 9.15 wt% MnO) occur in an elbaite-subtype pegmatite from the Drosendorf Complex (near Eibenstein an der Thaya, Bohemian massif, Austria). Based on geological and radiometrical data (337 +/- 5 Ma from Sm/Nd gamet-albite isochron) the pegmatite might be related to the Variscan Rastenberg...

The crystal structure of a pale blue transparent Mn-rich fluorapatite (MnO; 9.79 wt%) with the optimized formula- (Ca8.56Mn1.412+Fe0.012+P6O24F2.00 and space group P63/m,a=9.3429(3), c = 6.8110(2) Å, Z = 2 has been refined to R = 2.05% for 609 unique reflections (MoKα). The Mn in the Eibenstein an der Thaya. Austria apatite is strongly ordered at t...

Tourmaline has recently been shown to incorporate large amounts of substituent B at the tetrahedral site. To characterize the response of the tourmaline atomic arrangement to differing amounts of substitution of B for Si, five samples were separated from a core-to-rim (-3 mm) section of an Fe-bearing olenite with a dark green core and a nearly colo...

The core and rim of a short prismatic dark brown tourmaline crystal (10 mm in diameter) from a granitic pegmatite near Goslarn, Lower Austria, were structurally and chemically characterized, including H2O determination and Mössbauer analysis. The optimized formula, calculated using chemical and structural data for the core, is X(Na0.64Ca0.11K0020.2...

Chemical analysis (including light elements) of a Mn-rich tourmaline from a recently discovered locality near Eibenstein an der Thaya, Lower Austria, characterizes the sample as Mn-rich, Li-, and Fe-bearing olenite. Chemical analysis in combination with the crystal structure (a = 15.9325(5) Å, c = 7.1308(4) Å, R = 0.022) demonstrate that significan...

Chemical analyses and a crystal structure determination of light green tourmaline crystals from a marble near Friesach, Carinthia, show that this tourmaline belongs to a near end-member dravite with the highest Mg-content at the Y site of all previously investigated dravites. The composition was determined using electron microprobe data and atomic...

Recent discoveries have demonstrated that some synthetic and natural olenite tourmalines contain less than the putative Si-6.00 p.f.u., with the deficiencies in the tetrahedral sites being filled by excess boron (above B-3.00 p.f.u..), existing as B-[4]. Conversely, examination of the original study on natural olenite showed that B was assumed to b...

The first natural tourmaline (because tourmaline with [4]B has also been synthesized, we distinguish here between natural and synthetic tourmaline) that has been unequivocally demonstrated to contain B as a substituent at the T sites was described from Koralpe, Styria, Austria. This colourless B-rich olenite occurs as rims overgrowing schorl (black...

Distortion parameters [, 2 , DI(Y–O), DI(O–Y–O), DI(O–O)] have been calculated for cation polyhedra in tourmalines of different chemical compositions. Tourmalines with greater amounts of small, highly charged ions in the YO 6 octahedron display greater bond-length distortion in Y. The size and charge of the occupants at the Y site have been include...

Significant amounts of boron in both trigonal and tetrahedral coordination have been found through 11B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy of natural olenite (aluminum-rich tourmaline) from Stoffhütte, Koralpe, Styria, Austria. The 11B MAS NMR spectrum consists of a superposition of two quadrupolar MAS peaks. A...

A new empirically-determined formula for the calculation of the average T - O bond length (<T - O>) in tourmaline, including samples with [4]B, [4]Al, and [4]Fe3+, is given. The relationship shows that the <T - O> bond length can be determined with very good results by a complete chemical characterization (including Mössbauer study for Fe-bearing s...