gems, ancient gemology, ancient jewelry, turquoise, turquoise origin determination, Persia, Perisan turquoise, Iran, Nishapur, Neyshapour

This study compares turquoise CuAl₆(PO₄)₄(OH)₈·4H₂O from historic Iranian mines—Neyshapour, Damghan, and Kerman—with turquoise from other regional sources to identify characteristics that may help determine the origin of turquoise artifacts or jewelry. Samples of varying colors and turquoise jewels from the Musée des Arts Décoratifs de Paris (MAD) were analyzed using Raman and FTIR spectroscopy. While FTIR revealed no major differences among colors, Raman spectra showed sharper linewidths in blue turquoise, indicating greater structural order than in green samples, likely due to OH and H₂O vibrational mode sensitivity to compositional substitutions. Absorption spectroscopy showed even the best blue turquoise had minor Fe³⁺ absorption; color is primarily influenced by Cu²⁺ and Fe³⁺, with Fe²⁺ having negligible effect, and Fe³⁺ substitution for Al³⁺ turning the turquoise green. LIBS mapping allowed quick identification of turquoise, pyrite, and silicate phases, and revealed minor Al-Fe substitution. XRF analysis quantified major (Al, P, Cu) and trace elements (Fe, Zn, As, Ca, Ti). Correlation and PCA analyses combining measured and bibliographic data showed that MAD turquoise jewelry aligns with Neyshapour turquoise signatures, while Kerman and Chinese sources do not match. This suggests the MAD turquoise pieces dating before the 19th century likely originated in Persia.