Two modified smoky quartz centers in natural citrine

Maschmeyer, D.; Niemann, K.; Hake, Harald; Lehmann, Gerhard; Räuber, A.

doi:10.1007/bf00311051

Cited by 25 publications

(10 citation statements)

References 19 publications

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“…Since the temperatures required for electrolytic coloration are at least 300 K higher than those for exchange of these monovalent cations against each other, ionization of the A lO^ groups must be the highest energy barrier in this case. This activation energy is in reasonable agreement with the energies of the thermoluminescence emission associat ed with thermal destruction of smoky quartz centers formed by ionizing radiation: The emission maxima of 16100 and 21 500 cm "1 [13] correspond to 193 and 257 kJ/mol. The latter process is usually assumed to occur via excitation of electrons into the conduction band and their recombination with hole centers, i.e.…”

Section: Electrolysis Experimentssupporting

confidence: 71%

An Electrolytically Generated, Localized Hole Center in Quartz

Vassilikou‐Dova

Eftaxias

Lehmann

1989

Zeitschrift Für Naturforschung A

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In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed.An activation energy of 215 kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents.

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Section: Electrolysis Experimentssupporting

confidence: 71%

An Electrolytically Generated, Localized Hole Center in Quartz

Vassilikou‐Dova

Eftaxias

Lehmann

1989

Zeitschrift Für Naturforschung A

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“…Whether water inhibits amethyst formation, promotes citrine formation, or is coincidentally associated with another substituent cannot be determined from these data alone. However, Maschemeyer et al [1980] have proposed, based on EPR evidence, that the citrine color center is composed of a Li-Al smoky-type hole center, adjacent to a silicon vacancy. They suggest that one way to generate such a vacancy is by incorporating H20 in the Si site, with adjacent Si atoms moving to interstitial sites to minimize charge imbalance.…”

Section: Imentioning

confidence: 99%

Water in minerals? A peak in the infrared

Aines¹,

Rossman²

1984

J. Geophys. Res.

371

191

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Abstract. The study of water in minerals with infrared spectroscopy is reviewed with emphasis on natural and synthetic quartz. Water can be recognized in minerals as fluid inclusions and as isolated molecules and can be distinguished from hydroxide ion. The distinction between very small inclusions and aggregates of structurally bound molecules is difficult. New studies of synthetic quartz using near-infrared spectroscopy are reported. These demonstrate that water molecules are the dominant hydrogen containing species in synthetic quartz but that this water is not in aggregates large enough to form ice when cooled.

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“…Along with [AlO 4 ] 0 centers, small concentrations of other aluminum paramagnetic centers occur in quartz. For instance, citrine quartz contains centers characterized by a combination of Al ions and Li-H complexes (Samoilovich and Tsinober, 1969), as well as aluminum centers probably associated with oxygen vacancies (Maschmeyer et al, 1980;Maschmeyer and Lehmann, 1983). In the Subpolar Urals, such aluminum centers were detected in quartz of both citrine and smoky radiation coloring (Lyutoev, 1991).…”

Section: Resultsmentioning

confidence: 98%

Aluminum and germanium paramagnetic centers in vein quartz and rock crystals from the Subpolar Urals

2008

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The major economic types of vein quartz and rock crystals from the Subpolar Urals were studied using electron paramagnetic resonance. Quartz is characterized by widely variable concentrations of aluminum and germanium paramagnetic centers. The average values and ranges of these concentrations increase from older to younger generations of quartz. The lowest content of aluminum and germanium paramagnetic centers is typical of granulated and primary fine-grained quartz; in coarse-grained quartz and rock crystals, the content is much higher. According to the data obtained, granulated and primary fine-grained quartz should be regarded as a potentially high-quality raw material for glass melting, because these quartz varieties are distinguished by the lowest contents of alien structural centers. Once mineral impurities eliminated, high-quality quartz concentrate can be produced from this quartz.

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Two modified smoky quartz centers in natural citrine

Cited by 25 publications

References 19 publications

An Electrolytically Generated, Localized Hole Center in Quartz

An Electrolytically Generated, Localized Hole Center in Quartz

Water in minerals? A peak in the infrared

Aluminum and germanium paramagnetic centers in vein quartz and rock crystals from the Subpolar Urals

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