Raman and infrared spectroscopic study of turquoise minerals

Abstract

Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)(2-) units were observed.

Technical Evolution and Identification of Resin-Filled Turquoise

“…Infrared Spectroscopy. The untreated turquoise showed important bands in two ranges, from 3000-3600 cm -1 and 1800-400 cm -1 , which are typical variations of OH, H 2 O, and PO 4 according to previous research (Reddy et al, 2006;Chen and Qi, 2007;Chen et al, 2012;Cejka et al, 2015). The spectra of the resin-filled turquoise were characterized by the different combinations of turquoise and resin used in the treatment process.…”

Blue or green? turquoise–planerite species from Carico Lake Valley in Nevada, the United States: Evidence from Raman spectroscopy

“…The most intense marker band at approximately 1050 cm ‐1 , attributed to the ν 3 (PO 4 ) 3‐ mode, appears in the company of a series of bands in the 800–150 cm ‐1 range, which contains the symmetric bending mode ν 2 at ca 420 cm ‐1 and ν 4 at ca 570 cm ‐1. The presence of an apparent band at approximately 954 cm ‐1 (ν 1 ) in the green type (Figure ) indicates its higher crystallinity and structural organization, while the weak, wide bands in the 960–980‐cm ‐1 region are characteristic of many cryptocrystalline phosphates . In a range with lower energy, the most intense peaks are at 780 cm ‐1 and 562 cm ‐1 and 651 cm ‐1 and 539 cm ‐1 , for the blue and green varieties, respectively (Figure , Table S4).…”

“…The blue and green turquoise species filling in numerous veins intersecting the quartzites and cherts of the Valmy and Slaven Chert Formations or forming nodules on their surfaces are found abundantly in Carico Lake Valley . In the literature, some works on spectroscopic characteristics of turquoise minerals from various regions of the world, for example, Arizona, Senegal, Virginia, China, England, have been published yet . However, no one has focused on tracing differences with Raman microspectroscopy between variously coloured species coming from the same locality.…”

Preparation of novel blue phosphate pigments in imitation of turquoise

“…Therefore, novel blue pigment without harmful and precious metals is required. We focus on the natural ore, turquoise, CuAl 6 (PO 4 ) 4 (OH) 8 .4H 2 O, because this ore includes no harmful and precious metals [17,18]. Natural ores have high light stability and heat resistance.…”