“…Be 2+ is thus assumed to be 3 – Li + . For comparison, calculations on the basis of either 18 O and 3 Be, or 6 Si are shown in Table S3 and S4, respectively (Groat et al , 2008; Fridrichová et al , 2016; Lum et al , 2016).…”
Section: Resultsmentioning
confidence: 99%
“…Crystal channels are characterised by the wide C1/2a site between the rings and narrow C2/2b site of the interior of the tetrahedral [Si 6 O 18 ] 12– ring with diameters of ~5.2 Å and ~2.6 Å, respectively. Figure 8c shows C2 site occupation with Na + and associated type IId, IIs and I water configurations, with the distinct coordination of two water molecules to Na + (type IId), one water molecule and optionally C1 site occupation with CO 2 (type IIs), or the alkali cation free-water configuration (type I) (Fridrichová et al , 2016). Fig.…”
Section: Resultsmentioning
confidence: 99%
“…8.Crystal structure of beryl. (a) Along orientation parallel with respect to the c axis; (b) perpendicular with respect to the c axis, with octahedral A (Al), tetrahedral T2 (Be), Si, and two channel sites at the C1/2a (H 2 O, large alkali) and C2/2b (Na) positions; and (c) type IId, type IIs and type I H 2 O molecule configuration, with corresponding Na + and CO 2 positions on channel sites (after Fridrichová et al , 2016). …”
Beryl from Xuebaoding, Sichuan Province, western China is known for its unusual tabular habit and W–Sn–Be paragenesis in a greisen-type deposit. The crystals are typically colourless transparent to pale blue, often with screw dislocations of hexagonal symmetry on the (0001) crystal faces. Combining electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry with single-crystal X-ray diffraction (XRD), correlated with Raman and micro-infrared (IR) spectroscopy and imaging, the crystal chemical characteristics are determined. The contents of Na+ (0.24–0.38 atoms per formula unit (apfu)) and Li+ up to 0.38 apfu are at the high end compared to beryl from other localities worldwide. Li+ substitution for Be2+ on the tetrahedral (T2) site is predominantly charge balanced by Na+ on the smaller channel (C2) site, with Na+ ranging from 91.5% to 99.7% (apfu) of the sum of all other alkali elements. Cs+ and minor Rb+ and K+ primarily charge balance the minor M2+ substitution for Al3+ at the A site; all iron at the A site is suggested to be trivalent. The a axis ranges from 9.2161(2) to 9.2171(4) Å, with unit-cell volume from 678.03(3) to 678.48(7) Å3. The c/a ratio of 1.0002–1.0005 is characteristic for T2-type beryl with unit-cell parameters controlled primarily by Be2+ substitution. Transmission micro-IR vibrational spectroscopy and imaging identifies coordination of one or two water molecules to Na+ (type IIs and type IId, respectively) as well as alkali free water (type I). Based on IR absorption cross section and XRD a C1 site water content of 0.4–0.5 apfu is derived, i.e. close to 50% site occupancy. Secondary crystal phases with a decrease in Fe and Mg, yet increase in Na, suggest early crystallisation of aquamarine, with goshenite being late. With similar crystal chemistry to beryl of columnar habit from other localities worldwide, the tabular habit of Xuebaoding beryl seems to be unrelated to chemical composition and alkali content.
“…Be 2+ is thus assumed to be 3 – Li + . For comparison, calculations on the basis of either 18 O and 3 Be, or 6 Si are shown in Table S3 and S4, respectively (Groat et al , 2008; Fridrichová et al , 2016; Lum et al , 2016).…”
Section: Resultsmentioning
confidence: 99%
“…Crystal channels are characterised by the wide C1/2a site between the rings and narrow C2/2b site of the interior of the tetrahedral [Si 6 O 18 ] 12– ring with diameters of ~5.2 Å and ~2.6 Å, respectively. Figure 8c shows C2 site occupation with Na + and associated type IId, IIs and I water configurations, with the distinct coordination of two water molecules to Na + (type IId), one water molecule and optionally C1 site occupation with CO 2 (type IIs), or the alkali cation free-water configuration (type I) (Fridrichová et al , 2016). Fig.…”
Section: Resultsmentioning
confidence: 99%
“…8.Crystal structure of beryl. (a) Along orientation parallel with respect to the c axis; (b) perpendicular with respect to the c axis, with octahedral A (Al), tetrahedral T2 (Be), Si, and two channel sites at the C1/2a (H 2 O, large alkali) and C2/2b (Na) positions; and (c) type IId, type IIs and type I H 2 O molecule configuration, with corresponding Na + and CO 2 positions on channel sites (after Fridrichová et al , 2016). …”
Beryl from Xuebaoding, Sichuan Province, western China is known for its unusual tabular habit and W–Sn–Be paragenesis in a greisen-type deposit. The crystals are typically colourless transparent to pale blue, often with screw dislocations of hexagonal symmetry on the (0001) crystal faces. Combining electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry with single-crystal X-ray diffraction (XRD), correlated with Raman and micro-infrared (IR) spectroscopy and imaging, the crystal chemical characteristics are determined. The contents of Na+ (0.24–0.38 atoms per formula unit (apfu)) and Li+ up to 0.38 apfu are at the high end compared to beryl from other localities worldwide. Li+ substitution for Be2+ on the tetrahedral (T2) site is predominantly charge balanced by Na+ on the smaller channel (C2) site, with Na+ ranging from 91.5% to 99.7% (apfu) of the sum of all other alkali elements. Cs+ and minor Rb+ and K+ primarily charge balance the minor M2+ substitution for Al3+ at the A site; all iron at the A site is suggested to be trivalent. The a axis ranges from 9.2161(2) to 9.2171(4) Å, with unit-cell volume from 678.03(3) to 678.48(7) Å3. The c/a ratio of 1.0002–1.0005 is characteristic for T2-type beryl with unit-cell parameters controlled primarily by Be2+ substitution. Transmission micro-IR vibrational spectroscopy and imaging identifies coordination of one or two water molecules to Na+ (type IIs and type IId, respectively) as well as alkali free water (type I). Based on IR absorption cross section and XRD a C1 site water content of 0.4–0.5 apfu is derived, i.e. close to 50% site occupancy. Secondary crystal phases with a decrease in Fe and Mg, yet increase in Na, suggest early crystallisation of aquamarine, with goshenite being late. With similar crystal chemistry to beryl of columnar habit from other localities worldwide, the tabular habit of Xuebaoding beryl seems to be unrelated to chemical composition and alkali content.
“…[17][18][19] The six-membered rings are stacked vertically along the c-axis forming channels, where 'impurities' (Na, K, Cs or OH À , H 2 O, CO 2 , CH 4 ) can be accommodated. [19][20][21] Raman spectra were commonly used to learn about beryl and its varieties, to identify this mineral unambiguously. [16,22] Thorough analysis of a series of cut gemstones was made by Bersani et al [23] also to learn about presence of impurities and OH/H 2 O that can help in provenancing raw or cut gemstones.…”
Section: Introductionmentioning
confidence: 99%
“…From structural point of view, hexagonal rings are connected in beryl by the Be ions on tetrahedral sites and Al ions in octahedral sites . The six‐membered rings are stacked vertically along the c ‐axis forming channels, where ‘impurities’ (Na, K, Cs or OH − , H 2 O, CO 2 , CH 4 ) can be accommodated . Raman spectra were commonly used to learn about beryl and its varieties, to identify this mineral unambiguously .…”
In this paper, a series of beryl varieties with the accent on emeralds was investigated using seven portable Raman spectrometers equipped mainly with 785-and 532-nm excitation lasers. Additionally, one dual system and a new portable sequentially shifted excitation Raman spectrometer were applied. The advantage of using handheld instrumentation for investigations to be carried out outside the laboratory is well documented. For major part of beryls (emeralds and aquamarines), the most intense Raman bands are found at correct positions +/À2 to 4 cm À1 using all the instruments (with the exception of one). Unambiguous identification of beryls is ensured by obtaining the strong characteristic of Raman features (1070 and 686 cm À1 ) of the whole spectrum. Spectroscopic performance and differences existing between the instruments not only from the construction and ergonomic point of view are discussed. All the instruments tested EzRaman-I Dual (Enwave Optronics), RaPort (EnSpectr), FirstGuard (Rigaku), FirstDefender XL and FirstDefender RM (Thermo Scientific), Inspector Raman (Delta Nu) and Bravo (Bruker) can be used for common gemmological and mineralogical work in situ. Two instruments (the RaPort and the sequentially shifted excitation Raman spectrometer Bravo) allow recording excellent quality Raman spectra comparable with laboratory dispersive Raman microspectrometers.
Raman has long been established as a nondestructive and noninvasive technique that has found increasing application in the area of cultural heritage and the study of works of art. Here, we present a further application of Raman spectroscopy in the study of an oil painting belonging to the de Brécy Trust. In the work presented, Raman microscopy has been employed to spectroscopically study minute fragments of excised pigments from a small oil painting bearing the hallmarks of a study sketch by the famous English landscape artist John Constable. Raman spectra were collected from 18 discrete areas of the work, chosen due to their colour in order to potentially cover all of the pigments used in this work. Of the 18, six positive identifications were made, confirming that the painting contained pigments and minerals known to be favoured by the artist. Whilst the remaining 12 sample sites were complicated by the fluorescence effects observed from the applied varnish, this can be useful in providing evidence to support the application of the 'scumbling' technique known to be favoured by Constable. We have positively identified the pigments: ultramarine/lapis lazuli, lead white, red lead, Prussian blue, chrome yellow and ivory black. We have also identified amorphous carbon and gypsum. These positively identified pigments link into Constable's existing colour box and four palettes, providing evidence that could lead to the painting being attributed to Constable.
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