DISORDERED Mg-BEARING OLENITE FROM A GRANITIC PEGMATITE AT GOSLARN, AUSTRIA: A CHEMICAL, STRUCTURAL, AND INFRARED SPECTROSCOPIC STUDY

Ertl, Andreas; Hughes, John M.; Brandstätter, F.; Dyar, M. D.; Prasad, Pinnelli S. R.

doi:10.2113/gscanmin.41.6.1363

Cited by 30 publications

(21 citation statements)

References 11 publications

(32 reference statements)

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“…MacDonald and Hawthorne (1995) have shown that <T-O> distances in uvite, ideally Ca(Mg,Fe 2+ ) 3 (MgAl 5 )Si 6 O 18 (BO 3 ) 3 (F,OH) 4 , are in accord with the occurrence of Al at the T site, and structural work on other compositions (Bloodaxe et al 1999;Schreyer et al 2002;Cempírek et al 2006;Prowatke et al 2003;Ertl and Hughes 2002;Ertl et al 2003) also show small amounts of Al at the T site.…”

Section: Previous Workmentioning

confidence: 94%

The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and 27Al MAS NMR study

Lussier

Aguiar

Michaelis

et al. 2009

American Mineralogist

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Considerable uncertainty has surrounded the occurrence of tetrahedrally coordinated Al and B at the T site in tourmaline. Although previously detected in several tourmaline specimens, the frequency of these substitutions in nature, as well as the extent to which they occur in the tourmaline structure, is not known. Using 11 B and 27 Al MAS NMR spectroscopy, we have investigated the presence of B and Al at the T site in 50 inclusion-free tourmaline specimens of low transition-metal content and different species (elbaite, "fluor-elbaite," liddicoatite, dravite, uvite, olenite, and magnesiofoitite) from different localities worldwide. Chemical shifts of [4] B and [3] B in 11 B spectra, and [4] Al and [6] Al in 27 Al spectra, are well resolved, allowing detection of even small amounts of T-site constituents. In the observed spectra, [4] B and [3] B peaks are located at 0 and 18-20 ppm, respectively, with the greatest intensity corresponding to [3] B (=3 apfu). In 27 Al spectra, [4] Al and [6] Al bands are located at 68-72 and 0 ppm, respectively, with the greater intensity corresponding to [6] Al. However, inadequate separation of Y Al and Z Al precludes resolution of these two bands. Simulation of 11 B MAS NMR spectra shows that tetrahedrally and trigonally coordinated B can be readily distinguished at 14.1 T and that a [4] B content of 0.0-0.5 apfu is common in tourmaline containing low amounts of paramagnetic species. 27 Al MAS NMR spectra show that Al is also a common constituent of the T site in tourmaline. Determination of [4] Al content by peak-area integration commonly shows values of 0.0-0.5 apfu. Furthermore, the chemical shift of the 27 Al tetrahedral peak is sensitive to local order at the adjacent Y and Z octahedra, where [4] Al-Y Mg 3 and [4] Al-Y (Al,Li) 3 arrangements result in peaks located at ~65 and ~75 ppm, respectively. Both 11 B MAS NMR and 27 Al MAS NMR spectra show peak broadening as a function of transition-metal content (i.e., Mn 2+ + Fe 2+ = 0.01-0.30 apfu) in the host tourmaline. In 11 B spectra, broadening and loss of intensity of the [3] B signal ultimately obscures the signal corresponding to [4] B, increasing the limit of detection of [4] B in tourmaline. Our results clearly show that all combinations of Si, Al, and B: T = (Al, Si) 6 , T = (B, Si) 6 , T = (Al, B, Si) 6 , and T = Si 6 apfu, are common in natural tourmalines.

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Section: Previous Workmentioning

confidence: 94%

The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and 27Al MAS NMR study

Lussier

Aguiar

Michaelis

et al. 2009

American Mineralogist

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“…There has been considerable work done on the characterization (e.g. Hawthorne et al, 1993;Burns et al, 1994;Taylor et al, 1995;Dyar et al, 1998;Francis et al, 1999;Bloodaxe et al, 1999;Kalt et al, 2001;Cámara et al, 2002;Schreyer et al, 2002;Ertl and Hughes, 2002;Ertl et al, 2003aErtl et al, ,b, 2004Ertl et al, , 2005Hughes et al, 2000Marschall et al, 2004;Bosi et al, , 2005 and understanding (Hawthorne, 1996(Hawthorne, , 2002 of site occupancy in tourmaline. However, the complete derivation of site populations (and accurate bulk compositions) is not trivial, and our knowledge of the crystal chemistry of all the tourmaline minerals is still far from complete.…”

Section: Introductionmentioning

confidence: 99%

Mushroom elbaite from the Kat Chay mine, Momeik, near Mogok, Myanmar: I. Crystal chemistry by SREF, EMPA, MAS NMR and Mössbauer spectroscopy

et al. 2008

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Tourmaline from the Kat Chay mine, Momeik, near Mogok, Shan state, Myanmar, shows a variety of habits that resemble mushrooms, and it is commonly referred to as 'mushroom tourmaline'. The structure of nine single crystals of elbaite, ranging in colour from pink to white to black and purple, extracted from two samples of mushroom tourmaline from Mogok, have been refined (SREF) to R indices of~2.5% using graphite-monochromated Mo-Ka X-radiation. 11 B and 27 Al Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy shows the presence of [4] B and the absence of [4] Al in samples with transition-metal content low enough to prevent paramagnetic quenching of the signal. Site populations were assigned from refined site-scattering values and unit formulae derived from electron-microprobe analyses of the crystals used for X-ray data collection. 57 Fe Mössbauer spectroscopy shows that both Fe 2+ and Fe 3+ are present, and the site populations derived by structure refinement show that there is no Fe at the Z site; hence all Fe 2+ and Fe 3+ occurs at the Y site. The 57 Fe Mössbauer spectra also show peaks due to intervalence charge-transfer involving Fe 2+ and Fe 3+ at adjacent Y sites. Calculation of the probability of the total amount of Fe occurring as Fe 2+ ÀFe 3+ pairs for a random short-range distribution is in close accord with the observed amount of Fe involved in Fe 2+ ÀFe 3+ , indicating that there is no short-range order involving Fe 2+ and Fe 3+ in these tourmalines.

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“…The structure refi nement and chemical data obtained in this study by that method yields a structural formula for this synthetic Ag-bearing tourmaline of: In reference to tourmaline end-member species (Hawthorne and Henry 1999), we can describe this tourmaline as a mixture of olenite (51 mol%) and dravite (49 mol%). Hence, this tourmaline belongs to the olenite-dravite series as do the tourmaline samples described by Ertl et al (2003a). Refi ning Na ↔ Ag at the X site clearly indicates that Ag occupies this site (Table 3).…”

Section: Crystal Structurementioning

confidence: 73%

“…Substitution of Al for Mg at the Z site has been described by , Hawthorne et al (1993), MacDonald and Hawthorne (1995), Taylor et al (1995), Bloodaxe et al (1999), andErtl et al (2003a). Signifi cant amounts of Mg at the Z site are refl ected in the <Z-O> distance.…”

Section: Crystal Structurementioning

confidence: 94%

Synthetic Ag-rich tourmaline: Structure and chemistry

London

Ertl

Hughes

et al. 2006

American Mineralogist

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Ag-rich tourmaline crystals were synthesized at 750 °C, 200 MPa H 2 O, and f O 2 = 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% Ag 2 O was synthesized, and this is the fi rst time a tourmaline is described that contains signifi cant amounts of Ag at the ninefold-coordinated X site. Crystal structure refi nement and chemical analysis (EMPA) give the optimized formula X (Na 0.58 Ag 0.18 ■ ■ 0.24 ) Y (Al 1.54 Mg 1.46 ) Z (Al 5.34 Mg 0.66 ) T (Si 5.90 Al 0.10 )O 18 (BO 3 ) 3 V (OH) 3 W (O 0.53 F 0.47 ), with a = 15.8995(4) and c = 7.1577(4) Å, and R = 0.036 for a crystal (∼20 × 100 μm) with approximately 2.2 wt% Ag 2 O. Refi ning Na ↔ Ag at the X site clearly indicates that Ag occupies this site. The X-O2 distance of ∼2.52 Å is slightly longer than tourmaline with ∼(Na 0.6 ■ ■ 0.4 ), refl ecting the slightly larger ionic radius of Ag compared to Na. Releasing the occupancy at the Y site gives ∼Al 0.98 (∼12.7 e -), which can be explained by occupation of Mg and Al. On a bond-angle distortion vs. distance diagram, the Ag-rich olenite-dravite lies approximately on the V site = 3 (OH) line in the fi gure, defi ning the relation between bond-angle distortion (σ oct 2 ) of the ZO 6 octahedron and the distance. No H could be found at the O1 site by refi nement, in agreement with the Mg-Al disorder between the Y site and the Z site. Synthetic tourmaline contains no Ag when only AgCl is added; the compatibility of Ag in tourmaline, therefore, is largely a function of the F/Cl ratio of the fl uid medium. A positive association of Ag at the X site with Al at the Y site and with F suggests that tourmaline might be useful for exploration in Cornwall-type polymetallic ore deposits associated with F-rich peraluminous granites or at other Ag-, F-, and B-enriched deposits such as Broken Hill, Australia. Preliminary electron microprobe analyses of tourmaline from Cornwall and Broken Hill, however, failed to detect Ag at the 3σ detection level of 0.08 wt% Ag 2 O.

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DISORDERED Mg-BEARING OLENITE FROM A GRANITIC PEGMATITE AT GOSLARN, AUSTRIA: A CHEMICAL, STRUCTURAL, AND INFRARED SPECTROSCOPIC STUDY

Cited by 30 publications

References 11 publications

The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and 27Al MAS NMR study

The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and 27Al MAS NMR study

Mushroom elbaite from the Kat Chay mine, Momeik, near Mogok, Myanmar: I. Crystal chemistry by SREF, EMPA, MAS NMR and Mössbauer spectroscopy

Synthetic Ag-rich tourmaline: Structure and chemistry

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