Amethyst and morion quartz gemstone raw materials from Turkey: color saturation and enhancement by gamma, neutron and beta irradiation

Hatipoğlu, Murat; Helvacı, Cahit; Kibar, R.; Çetin, A. Enis; Tuncer, Y.; Can, N.

doi:10.1080/10420150.2010.489611

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…The other bands centered at 435, 480, 620, and 635 nm in the visible wavelength region may be ascribed to substitutional Co, Ni, Cu, Zn, Zr, Mo transition metal elements. In addition, in the ultraviolet wavelength region, the unique absorption peak centered at 375 nm should be matched to the substitution of Al for Si because it has been reported in many previous papers that the strong and distinctive band centered at about 375 nm in a quartz spectrum can be the corresponding band for Al 3+ in octahedral coordination (6,18,19,21,22,31). Lastly, the absorption band centered at 760 nm in the infrared wavelength region could be ascribed to different imperfections beside impurities, and could mainly be due to gamma radiation-induced oxygen defects.…”

Section: Resultsmentioning

confidence: 97%

Spectral, electron microscopic and chemical investigations of gamma-induced purple color zonings in amethyst crystals from the Dursunbey-Balıkesir region of Turkey

Hatipoğlu

Kibar

Çetin

et al. 2011

Radiation Effects and Defects in Solids

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Amethyst crystals on matrix specimens from the Dursunbey-Balıkesir region in Turkey have five representative purple color zonings: dark purple, light purple, lilac, orchid, and violet. The purple color zonings have been analyzed with optical absorption spectra in the visible wavelength region, chemical full trace element analyses (inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectroscopy), and scanning electron microscopic images with high magnification. It can be proposed that the production of the purple color in amethyst crystals is due to three dominant absorption bands centered at 375, 530, and 675 nm, respectively. In addition, the purple color zonings are also due to four minor absorption bands centered at 435, 480, 620, and 760 nm. X-ray diffraction graphics of the investigated amethyst crystals indicate that these crystals are composed of a nearly pure alpha-quartz phase and do not include any moganite silica phase and/or other mineral implications. Trace element analyses of the amethyst crystals show five representative purple color zonings, suggesting that the absorption bands can be mainly attributed to extrinsic defects (chemical impurities). However, another important factor that influences all structural defects in amethyst is likely to be the gamma irradiation that exists during amethyst crystallization and its inclusion in host materials. This gamma irradiation originates from the large underlying intrusive granitoid body in the region of amethyst formation. Irradiation modifies the valence values of the impurity elements in the amethyst crystals. It is observed that the violet-colored amethyst crystals have the most stable and the least reversible coloration when exposed to strong light sources. This situation can be related to the higher impurity content of Fe (2.50 ppm), Co (3.1 ppm), Ni (38 ppm), Cu (17.9 ppm), Zn (10 ppm), Zr (3.9 ppm), and Mo (21.8 ppm).

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Section: Resultsmentioning

confidence: 97%