Compositional variation of turquoise-group minerals from the historical collection of the Real Museo Mineralogico of the University of Naples

Abstract

Five turquoise samples, belonging to the XVII century historical collection of the Real Museo Mineralogico (University of Naples Federico II), were investigated by a multi-methodological approach based on powder X-ray diffraction, electron microprobe analysis in wavelength-dispersive spectroscopy mode, backscattered electron images from scanning electron microscopy in energy-dispersive spectroscopy mode, laser ablation inductively coupled plasma mass spectrometry, Fourier transform infrared and Raman spectroscopy.The samples originate from Sinai (Egypt), Santa Fè S. Miguel (New Mexico), Saxony (Germany), Montebras Creuse (France) and Nishapur (Khorassan, Iran) and display different mineralogical compositions and various mineral associations. The study has shown the presence of: (1) four minerals of the turquoise group: turquoise, faustite, chalcosiderite and planerite; (2) other phosphates from different groups: wavellite, crandallite, goyazite, gorceixite, variscite, metavariscite, fluorapatite; and (3) other minerals: voltaite, adularia and quartz.The present investigation is intended to show the mineralogical and geochemical variability of the samples with particular attention to the mineralogical parageneses, textural analyses and trace-element concentrations.

Unique Raindrop Pattern of Turquoise from Hubei, China

“…Yang et al (2003) and Hull et al (2008) discovered apatite inclusions in turquoise from Ma'anshan in Anhui Province and the Castilian mine in New Mexico, respectively. Additionally, fluorapatite also occurred in turquoise from Nishapur, Iran (Rossi et al, 2017). However, this study was the first to find fluorapatite coexisting with turquoise from Hubei Province, (PO 4 ) 3 F], was an occasional turquoise imitation used in art objects or historical jewels and previously considered turquoise (Reiche et al, 2001;Krzemnicki et al, 2011).…”

“…Researchers have made great effort to investigate gem turquoise's gemological and mineralogical characteristics (Abdu et al, 2011;Chen et al, 2012;Čejka et al, 2015;Rossi et al, 2017), color origin (Zhang et al, 1982;Luan et al, 2004;Reddy et al, 2006), and concentration of trace elements and rare earth elements (Wang et al, 2007;She et al, 2009;He et al, 2011;Rossi et al, 2017;Shirdam and Aslani, 2017). Additionally, the identification characteristics of treated and imitation turquoise have drawn many researchers' attention (Moe et al, 2007;Krzemnicki et al, 2011;Bernardino et al, 2016;Schwarzinger and Schwarzinger, 2017;Xu and Di, 2018;Liu et al, 2019b).…”

Provenancing turquoise: a difficult task

“…Some vibrational spectroscopy studies have been conducted on gem phosphates, and turquoise in particular (Čejka et al, 2015;Dumańska-Słowik et al, 2019;Fritsch et al, 2019;Reddy et al, 2006;Rossi et al, 2017). The detailed study by Čejka et al (2015) is based on only three samples, two from the United States and one from Senegal.…”

Core–Double-Shell Fe2O3@SiO2@Jarosite Hybrid Nanoparticles Synthesized by Laser Ablation of Turquoise in Ethanol

“…Turquoise is a precious mineral which belongs to a group of inorganic materials with at least six recognized members . The general formula of the turquoise group was written as AB 6 (PO 4 ) n (PO 3 )­(OH) 2 n −1 (OH) 8 ·4H 2 O, wherein the A position was filled with Cu 2+ or Fe 2+ as the most common constituent, while Fe 3+ and Al 3+ are situated at the B position . Turquoise might also have veins running through it.…”

“…24 The general formula of the turquoise group was written as AB 6 (PO 4 ) n (PO 3 )(OH) 2n−1 (OH) 8 •4H 2 O, wherein the A position was filled with Cu 2+ or Fe 2+ as the most common constituent, while Fe 3+ and Al 3+ are situated at the B position. 25 Turquoise might also have veins running through it. The wide veins on the surface of turquoise are undesired for high-quality designing of jewelry pieces.…”