Il lapislazzuli è una pietra semi-preziosa usata fin dal 7000 a.C per la lavorazione di artefatti e gioielli. Lo studio di questa pietra blu è importante per ottenere informazioni sulla provenienza dei materiali e aiutare storici e archeologi a ricostruire le antiche rotte commerciali. Infatti, a causa delle complesse condizioni geologiche in cui il lapislazzuli può formarsi, solo un numero ristretto di giacimenti esiste nel mondo. Le miniere afghane nella regione del Badakhshan sono considerate le fonti principali di lapislazzuli in tempi antichi, ma non si può escludere che altri giacimenti possano essere stati utilizzati in passato. Per risolvere la questione un progetto di ricerca a lungo termine è stato avviato nel 2007 dalle Università di Torino e Firenze, l'Istituto Nazionale di Fisica Nucleare (INFN) e il Museo di Storia Naturale di Firenze ed è stato infine proposto un protocollo per determinare la provenienza delle rocce di lapislazzuli. Il presente lavoro di tesi è parte di questo progetto di ricerca e si propone di aumentare la statistica dei dati presenti nel protocollo e di trovare nuovi marker di provenienza. Particolare importanza è data a campioni provenienti dai siti archeologici di Shahr-i Sokhta e Kerman (Iran). Inizialmente viene impiegato un microscopio digitale per fotografare e determinare la texture e l'assemblaggio mineralogico dei campioni. La CatodoLuminescenza a freddo (cold-CL) viene poi eseguita su sezioni lucidate dei campioni per individuare le diverse fasi mineralogiche attraverso un contrasto di colori dovuto alla loro diversa luminescenza. Si pone particolare attenzione a due fasi mineralogiche, il diopside e la pirite, i cui elementi di traccia sono essenziali per l'applicazione del protocollo di analisi. La macro Fluorescenza a Raggi X (XRF) viene poi impiegata sulle aree blu dei campioni per determinarne la composizione elementale. In secondo luogo viene applicata su alcuni campioni una tecnica non ancora presente nel protocollo. La Spettroscopia di Riflettanza a Fibre Ottiche (FORS) viene già impiegata per distinguere tra blu oltremare naturale e sintetico. Questo pigmento si ottiene storicamente dalla polverizzazione delle rocce di lapislazzuli, ma dal 1826 ne esiste una versione artificiale. In questo lavoro di tesi la tecnica FORS viene utilizzata nel range UV-VIS-NIR su zone il più omogeneamente blu, sia per le rocce di reference sia per i campioni archeologici, per determinare se andamenti diversi negli spettri possano discriminare le diverse provenienze dei lapislazzuli.
Lapis lazuli is a semi-precious stone used since 7000 BCE for the manufacturing of carved artefacts and jewels. The study of this blue stone is important to find out information about the provenance of the material and to help historians and archaeologists in the reconstruction of ancient trade routes. Indeed, due to the low probability of the occurrence of geological conditions in which lapis lazuli can form, only a few quarries exist in the world. The Afghan mines in the region of the Badakhshan are widely considered the main sources of lapis lazuli in ancient times, though other quarries could have possibly been exploited since antiquity. To solve the question, a long-term research project was started in 2007 by the University of Torino and the Istituto Nazionale di Fisica Nucleare (INFN) in collaboration with the Museum of Natural History and the University of Firenze and a protocol to determine the provenance of lapis lazuli rocks was then proposed and presented. The present thesis work is part of this research project and is dedicated to increasing the statistics of the data included in the proposed protocol and finding other significant provenance markers. Particular relevance is given to some samples from the archaeological sites of Shahr-i Sokhta and Kerman (Iran). At first, a digital microscope is used to determine the texture and the mineralogical assemblage of the samples. Cold-CathodoLuminescence (cold-CL) is then carried out on polished cross sections of the samples in order to visually determine the various mineralogical phases thanks to their different luminescence. Particular attention is paid to two phases, diopside and pyrite, whose trace elements are essential for the application of the proposed protocol. Macro X-Ray Fluorescence (XRF) is performed on the most homogeneous blue areas to determine the elemental composition of the samples. Secondly, a different approach, not present yet in the protocol, is carried out on some samples. Fiber Optics Reflectance Spectroscopy (FORS) is already used to give some useful information for the discrimination of natural and synthetic ultramarine blue, a pigment historically obtained by crushing and grinding the lapis lazuli rocks, of which an artificial version has been created in 1826. In this thesis work FORS is used in the UV-VIS-NIR range on both database rocks and archaeological samples on the most homogeneous blue areas in order to understand if different features can be observed between various provenances.
Application of X-ray Fluorescence, Fiber Optics Reflectance Spectroscopy and Cathodoluminescence imaging in provenance studies of lapis lazuli
MARABOTTO, MIRIANA
2020/2021
Abstract
Lapis lazuli is a semi-precious stone used since 7000 BCE for the manufacturing of carved artefacts and jewels. The study of this blue stone is important to find out information about the provenance of the material and to help historians and archaeologists in the reconstruction of ancient trade routes. Indeed, due to the low probability of the occurrence of geological conditions in which lapis lazuli can form, only a few quarries exist in the world. The Afghan mines in the region of the Badakhshan are widely considered the main sources of lapis lazuli in ancient times, though other quarries could have possibly been exploited since antiquity. To solve the question, a long-term research project was started in 2007 by the University of Torino and the Istituto Nazionale di Fisica Nucleare (INFN) in collaboration with the Museum of Natural History and the University of Firenze and a protocol to determine the provenance of lapis lazuli rocks was then proposed and presented. The present thesis work is part of this research project and is dedicated to increasing the statistics of the data included in the proposed protocol and finding other significant provenance markers. Particular relevance is given to some samples from the archaeological sites of Shahr-i Sokhta and Kerman (Iran). At first, a digital microscope is used to determine the texture and the mineralogical assemblage of the samples. Cold-CathodoLuminescence (cold-CL) is then carried out on polished cross sections of the samples in order to visually determine the various mineralogical phases thanks to their different luminescence. Particular attention is paid to two phases, diopside and pyrite, whose trace elements are essential for the application of the proposed protocol. Macro X-Ray Fluorescence (XRF) is performed on the most homogeneous blue areas to determine the elemental composition of the samples. Secondly, a different approach, not present yet in the protocol, is carried out on some samples. Fiber Optics Reflectance Spectroscopy (FORS) is already used to give some useful information for the discrimination of natural and synthetic ultramarine blue, a pigment historically obtained by crushing and grinding the lapis lazuli rocks, of which an artificial version has been created in 1826. In this thesis work FORS is used in the UV-VIS-NIR range on both database rocks and archaeological samples on the most homogeneous blue areas in order to understand if different features can be observed between various provenances.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14240/67707