Distinguishing natural from synthetic amethyst: the presence and shape of the 3595 cm−1 peak

Karampelas, Stefanos; Fritsch, Emmanuel; Zorba, T.; Paraskevopoulos, K. M.; Sklavounos, Spyros

doi:10.1007/s00710-005-0101-9

Cited by 16 publications

(36 citation statements)

References 6 publications

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“…Of special interest is the discrete band at 3585 cm −1 which is prominent in room temperature and ~123 K measurements. It should be noted that the 3595 cm −1 band discussed by Niimi et al [] and Gleason and De Sisto [] is a different absorption band than the 3585 cm −1 band referred to here [e.g., Karampelas et al, ].…”

Section: Discussionsupporting

confidence: 91%

“…The 3585 cm À1 absorption band is found in synthetic quartz crystals [Wood, 1960;Kats et al, 1962;Dodd and Fraser, 1965;Kopp and Staats, 1970; Lehmann, 1976a, 1976b;Halliburton et al, 1981;Kekulawala et al, 1981;Subramaniam et al, 1984; Doukhan, 1989, 1991;Pankrath, 1991;Bachheimer, 1998;Muto et al, 2011]. It is prominent in amethyst and citrine Lehmann, 1976a, 1976b;Chakraborty and Lehmann, 1978;Rovetta, 1989;Karampelas et al, 2005] and in chalcedony and microcrystalline quartz [Frondel, 1982; Journal of Geophysical Research: Solid Earth 10.1002/2016JB013533 Acknowledgments…”

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confidence: 99%

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Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes

et al. 2017

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Natural quartz single crystals were experimentally deformed in two orientations: (1) ⊥ to one prism plane and (2) in O+ orientation at 900 and 1000°C, 1.0 and 1.5 GPa, and strain rates of ~1 × 10−6 s−1. In addition, hydrostatic and annealing experiments were performed. The starting material was milky quartz, which consisted of dry quartz with a large number of fluid inclusions of variable size up to several 100 µm. During pressurization fluid inclusions decrepitated producing much smaller fluid inclusions. Deformation on the sample scale is anisotropic due to dislocation glide on selected slip systems and inhomogeneous due to an inhomogeneous distribution of fluid inclusions. Dislocation glide is accompanied by minor dynamic recovery. Strongly deformed regions show a pointed broad absorption band in the ~3400 cm−1 region consisting of a superposition of bands of molecular H2O and three discrete absorption bands (at 3367, 3400, and 3434 cm−1). In addition, there is a discrete absorption band at 3585 cm−1, which only occurs in deformed regions and reduces or disappears after annealing, so that this band appears to be associated with dislocations. H2O weakening in inclusion‐bearing natural quartz crystals is assigned to the H2O‐assisted dislocation generation and multiplication. Processes in these crystals represent recycling of H2O between fluid inclusions, cracking and crack healing, incorporation of structurally bound H in dislocations, release of H2O from dislocations during recovery, and dislocation generation at very small fluid inclusions. The H2O weakening by this process is of disequilibrium nature because it depends on the amount of H2O available.

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Section: Discussionsupporting

confidence: 91%

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confidence: 99%

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes

et al. 2017

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“…Karampelas at al. 23 proposed that this band can be used to help the distinguishing of natural from synthetic amethyst, because it is present in most natural but absent in most synthetic amethyst, but they didn't discuss its nature. Figure 4 shows the infrared spectra before and after irradiation.…”

Section: Resultsmentioning

confidence: 99%

Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation

Lameiras

Nunes²,

Vasconcelos

2009

Mat. Res.

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The infrared bands of amethyst and prasiolite samples from different origins were correlated to the trace elements contents. Amethysts have an iron content greater than 20 ppm and a low content of sodium and potassium. Prasiolites have an aluminum content greater than 120 ppm and a higher overall trace elements content, which accounts for a strong absorption between 3200 and 3600 cm 0 centers formed by the exposure to ionizing irradiation and to the influence of lattice distortions due to the content of iron as a substitute for silicon and a high content of trace elements of large ionic radius like potassium.

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“…The impact of this is a lack of confidence from the buyers and has prompted much research into identifying the synthetic material with certainty. In particular, arguments based on the presence or the absence of certain infrared absorption bands proved promising (Fritsch et al 1987a, Fritsch et al 1988a, Fritsch et al 1995, Notari et al 2001, Smaali, 1998, Zecchini et al 1999, Karampelas et al 2005. The most recent argument (Karampelas et al 2005) is tested in this paper on a large number of samples.…”

Section: Introductionmentioning

confidence: 79%

An Update in the Separation of Natural From Synthetic Amethysts

et al. 2007

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Since the first synthetic amethyst was commercially manufactured about 30 years ago, the separation from natural material has been difficult for gemologists. Even today, the separation of natural from hydrothermally grown in K2C03 synthetic amethyst is still an issue. With only the help of classical gemological criteria (such as inclusions, twinning and color zoning) it is difficult to separate synthetic stones from their natural counterparts. The separation problem is even more complex in the case of the highest quality (and value) of amethysts presenting neither inclusion nor twinning nor color zoning. IR absorption spectra of amethyst in the region of the ΧΟΗ group stretching (particularly from 3000 to 3900 cm'1) reveal several bands that have been used for the separation of natural from synthetic amethyst. Using a resolution at 0.5 cm the 3595 cm1 band is present in all natural amethyst and in some rare synthetic ones. When present in synthetic amethysts, its full width at half maximum (FWHM) is about 7 cm , whereas it is about 3.3 cm' in all naturals. This new criterion worked for all of our samples.

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Distinguishing natural from synthetic amethyst: the presence and shape of the 3595 cm−1 peak

Cited by 16 publications

References 6 publications

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes

Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation

An Update in the Separation of Natural From Synthetic Amethysts

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Distinguishing natural from synthetic amethyst: the presence and shape of the 3595 cm−1 peak

Cited by 16 publications

References 6 publications

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H2O‐weakening processes

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H2O‐weakening processes

Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation

An Update in the Separation of Natural From Synthetic Amethysts

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Product

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Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H₂O‐weakening processes