An innovative method An innovative method An innovative method

Document Type : Original Article

Authors

1 Geology Department, Faculty of Sciences, Ferdowsi University of Mashhad, Iran

2 M.Sc., in Applied Gemmology and Industrial Minerals, University of Ferdowsi, Mashhadnd,Iran

10.22067/gemiran.2026.48050
Abstract
   An innovative method was developed to evaluate the feasibility of combining artificial intelligence (AI) and advanced methods to standardize high-quality turquoise from the Neyshabur mine. Initially, conventional methods in gem identification and artificial intelligence were used to identify turquoise, then advanced gemological methods were used for standardization.
   The gemological characteristics of turquoise were determined with the help of digital image analysis and artificial intelligence (AI). This method relies on image processing by artificial intelligence (AI). 1600 digital image series of 18 samples from different areas of the Neyshabur turquoise mine were prepared and transferred to the database. The accuracy of turquoise gemstone identification using this method was 94%. With the help of XRD analyses, mineral identification, crystal structure determination, phase determination, and crystal particle size determination were possible. The average particle size of lower quality turquoise was 201.2 °A and gem quality turquoise was 137.9 °A calculated by Debye-Scherer formula. The identified Raman peaks are in the ranges of 200 cm1-, 400 cm1- and 1000 cm1-. The peaks at 1031 cm1-and 1036 cm1-are related to phosphate vibrations, but the peaks in the range of 1-200 cm1- are probably related to water or hydroxyl vibrations in the structure. Turquoise samples examined by SEM showed that low quality turquoises contain Si and Ca elements in addition to their main elements.
   Comparison of RAMAN, XRF, XRD and SEM analyses of turquoise from Neyshabur mine with turquoise from other regions of the world showed that turquoise from Neyshabur mine has its own unique XRD pattern that is significantly different from that of turquoise from other regions of the world. These differences are also clearly visible in RAMAN, XRF and SEM data analyses. This research showed that the turquoise gemstone from the Neyshabur mine (of gem quality) should be introduced as the world's standard turquoise reference.

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Abdu, Y. A.; Hull, S. H.; Fayek, M. And Hawthorne, F. C. (2011) The turquoise-chalcosiderite Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O solid-solution series: A Mössbauer spectroscopy, XRD, EMPA, and FTIR study. American Mineralogist, Volume 96, pages 1433–1442.
Cid-Dressner, H. (1965) Determination and refinement of the crystal structure of turquois, CuAl6(PO4)4(OH)8 • 4H2O. Zeits. Krist., 121, 87–113.
Foord, E.E. and J.E. Taggart, Jr. (1998) A reexamination of the turquoise group: the mineral aheylite, planerite (redefined), turquoise and coeruleolactite. Mineral. Mag., 62, 93–111.
King. J. R (2002) Mineral explained, Turquoise. Geology Today, Vol. 18, No. 3.
Kolitsch, U. and Giester, G. (2000) The crystal structure of faustite and its copper analogue turquoise.
Jagannatha Reddy. B, Ray L. Frost, Matt L. Weier and Wayde N. Martens (2006) Ultraviolet-visible, near infrared and mid infrared reflectance spectroscopy of turquoise.
Liu, X.; Lin, C.; Li, D.; Zhu, L.; Song, S.; Liu, Y.; Shen, C. (2018) Study on Mineralogical and Spectroscopic Characteristics of Turquoise from Hami, Xinjiang. Spectrosc. Spectr. Anal. 38, 1231–1239.
Mousavipak, N. (2020) Physico-chemical characterization of Iranian turquoise: a tentative to trace middle-eastern turquoise-bearing artifacts.
Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy, (7th edition), v. II, 946–951.
Schaller W.T. (1912) Crystallized Turquoise from Virginia.
Xueding Wang and Ying Guo (2020) The impact of trace metal cations and absorbed water on colour transition of turquoise.
Zhang, Y.; Shi, G. (2025) Big Data and AI-Enabled Construction of a Novel Gemstone Database: Challenges, Methodologies, and Future Perspectives. Minerals, 15, 1149.

  • Receive Date 13 April 2026
  • Publish Date 21 March 2026