Color Center in Amethyst Quartz

@article{Lehmann1966ColorCI,
  title={Color Center in Amethyst Quartz},
  author={Gerhard Lehmann and Walter J. Moore},
  journal={Science},
  year={1966},
  volume={152},
  pages={1061 - 1062}
}
Treatment with x-rays increased the intensity of color of natural amethyst up to fivefold, and an electron paramagnetic resonance spectrum was detected. The intensity of the spectrum was proportional to the intensity of the optical absorption near 545 m�. The EPR spectrum of the color center corresponded to a positive hole trapped on a substitutional Fe3+ ion in the quartz structure. We ascribe the color to a charge-transfer transition, Fe4+ + O2— → Fe3+ + O1-. 
A Fe K-edge XAS study of amethyst
An X-ray absorption spectroscopy (XAS) study of the Fe local environment in natural amethyst (a variety of α-quartz, SiO2) has been carried out. Room temperature measurements were performed at the Fe
Electron paramagnetic resonance spectroscopy of Fe3+ ions in amethyst: thermodynamic potentials and magnetic susceptibility
Single-crystal and powder electron paramagnetic resonance (EPR) spectroscopic studies of natural amethyst quartz, before and after isochronal annealing between 573 and 1,173 K, have been made from 90
Optical absorption of the d4 ion Fe4+ in pleochroic amethyst quartz
Optical absorption spectra have been taken at 300K for samples of amethyst quartz that show anomalous pleochroism instead of dichroism. The transition moment of the 945 nm band is parallel to a
ESR of an S=2 centre in amethyst quartz and its possible identification as the d4 ion Fe4+
A paramagnetic centre having spin S=2 and C2 symmetry has been detected in natural amethyst crystals. The only ESR transition observed was the Delta M=+or-4 transition between the lowest two energy
Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation
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
EPR Spectrum of Fe3+ in Synthetic Brown Quartz
A detailed description is given of the EPR spectrum of Fe3+ in synthetic brown quartz (the so‐called I center, presumed to be interstitial). There are three equally populated sites differing only in
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References

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Paramagnetic Resonance and Optical Properties of Amethyst
Color centers in amethyst are produced by action of ionizing radiation on precursor centers which arise from substitution of Fe3+ for Si4+ in the α‐quartz structure, with charge neutralization
The Spectra and Electronic Structure of the Tetrahedral Ions MnO4−, CrO4−−, and ClO4−
We have made use of a semiempirical treatment to calculate the energies of the molecular orbitals for the ground state and the first few excited states of permanganate, chromate, and perchlorate
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    Chem
    • ISod.
    • 1956