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<p>Optical absorption spectroscopic investigation of a zircon from Afghanistan, unique in both size and color, show evidence that it represents a new type of purple color in this mineral. By microprobe and laser ablation-inductively coupled plasm (LA-ICP-MS) mass spectrometry analyses, the material is nearly pure ZrSiO<sub>4</sub>. The contents of Nb, P, F, Na and Mn are under the detection limits in all point analyses. The mean values of K, Ca, Ti, Sm, Gd, Pb and Ho contents are below 0.001 apfu. The dark-purple, nearly black color of the zircon is thermally unstable. At annealing from 400 to 900&#xa0;°C it gradually vanishes due to decrease of intensities of the high-energy absorption edge, the broad absorption bands with maxima at ~ 17,970 and 23,900&#xa0;cm<sup>− 1</sup> (E⊥c) and ~ 18,620, 23,680 and 26,240&#xa0;cm<sup>− 1</sup> (E||c). Intensities of the weak narrow lines of absorption, which are very likely caused by electronic spin-forbidden <i>ff</i>-transitions of uranium and REE ions, remain unchanged. The origin of the zircon is unclear. By <sup>206</sup>Pb/<sup>238</sup>U radiometric age ~ 1909&#xa0;million years, it is Proterozoic.</p>

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On the color of a large dark-purple crystal of zircon from Afghanistan

  • 期刊论文

  • 发表日期：

    2026年7月16日

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  • Michail Taran,
  • Volodymyr Khomenko,
  • Ievgen Naumenko,
  • Jörg Nissen,
  • Martin Kutzschbach

摘要

Optical absorption spectroscopic investigation of a zircon from Afghanistan, unique in both size and color, show evidence that it represents a new type of purple color in this mineral. By microprobe and laser ablation-inductively coupled plasm (LA-ICP-MS) mass spectrometry analyses, the material is nearly pure ZrSiO4. The contents of Nb, P, F, Na and Mn are under the detection limits in all point analyses. The mean values of K, Ca, Ti, Sm, Gd, Pb and Ho contents are below 0.001 apfu. The dark-purple, nearly black color of the zircon is thermally unstable. At annealing from 400 to 900 °C it gradually vanishes due to decrease of intensities of the high-energy absorption edge, the broad absorption bands with maxima at ~ 17,970 and 23,900 cm− 1 (E⊥c) and ~ 18,620, 23,680 and 26,240 cm− 1 (E||c). Intensities of the weak narrow lines of absorption, which are very likely caused by electronic spin-forbidden ff-transitions of uranium and REE ions, remain unchanged. The origin of the zircon is unclear. By 206Pb/238U radiometric age ~ 1909 million years, it is Proterozoic.