ABSTRACT
Due to a variety of the enhancement and treatment turquoises discovered in gem markets, the identification of turquoise is becoming more and more difficult. By using laser Raman spectroscopy analysis, the characteristics of Raman spectra of the pressed and filled turquoises were studied. The results show that laser Raman spectroscopy is an effective technique to identify the enhancement and treatment turquoises and the natural ones, moreover, it's a non-destructive testing method. The Raman spectra of the enhancement and treatment turquoises are resulted mainly from the vibrational mode and frequency of water, hydroxyl units, PO4 tetrahedron and CH2 units. Besides, they have the characteristic Raman spectra peaks at 2,937, 2,883 and 1,451 cm(-1) which are attributed to the stretching vibration and the bending vibration of CH2, respectively. These characteristic Raman vibration bands, it will help to distinguish the natural turquoises and the treatment ones. The study provides a new train of thought on the rapid, accurate, and non-destructive identification of turquoise.
ABSTRACT
In the present paper, different-generation hydrothermally grown KTP crystals were tested by the Nicolet 550 type FIR spectrometer with the reflective technique. They were studied on different crystal faces. Since the hydrothermally grown KTP crystal usually grows (100), (011) and (201) crystal faces, these faces were tested in different-generation products, and they were tested by two spectral wave bands, 2 000-4 000 and 400-2 000 cm(-1). The figures were compared with the flux-melt grown KTP crystal. In addition, making reference to the method of calculation about the consistence of OH- in quartz, the consistence of OH- in different -generation hydrothermally grown KTP crystals was estimated. In the hydrothermal grown KTP crystals, the stretching vibration of OH- shows distinct directivity characteristic. The absorption at [100] direction is obvious and the frequency is about 30 cm(-1) higher than the flux-melt grown KTP. Each new generation weakened the consistency of OH-, which restrained the growth of the KTP crystal. Accordingly, increasing the purity of rough materials plays a very important role in improving the quality of the crystals.
ABSTRACT
The Raman spectrum has been employed to discuss the explanation of the structure of water and the vibration of [PO4(3-)] tetrahedron of the turquoise from Hubei and Anhui province. The Raman spectra are resulted mainly from vibrations of water, hydroxyl units and [PO4(3-)] tetrahedron of turquoise. The 3 510-3 440 cm(-1) bands with the main Raman spectra peak at 3 470 cm(-1) were assigned to the upsilon(OH) stretching vibrations and the 3 290-3 070 cm(-1) bands assigned to the upsilon(H2O) stretching vibrations. The bands observed at 1 200-1 030 cm(-1) with the strong peak at 1 039 cm(-1) were assigned to upsilon3 (PO4) antisymmetric stretching vibrations. And the Raman spectra peaks at 650-540 cm(-1) and 500-410 cm(-1) were attributed to the upsilon4 and upsilon2 bending vibrations of [PO4(3-)] tetrahedron, respectively. The spectra of the turquoise from different localities are basically similar and subtly different.
ABSTRACT
The object of the present study is the synthetic jadeite jade produced by American General Electric Corporation. Fourier transform infrared spectroscopy (FTIR) and Laser Raman spectroscopy were used to test its spectral properties in order to examine the feature of this kind of synthetic jadeite jade by vibrational spectroscopy and to figure out the mark for discriminate synthetic jadeite jade from natural jadeite jade. The study shows that GE synthetic jadeite jade is identical with natural jadeite jade in the main on fingerprint region in FTIR; There are clearly differences in the 2 000 -4 000 cm(-1) functional region in FTIR: a group of frequencies at 3 375, 3 471 and 3 614 cm(-1) indicate vibration absorption of O-H. GE synthetic jadeite jade has proven consistent with natural jadeite jade in the laser Raman spectra by a group of sharp scattering peaks at 376, 700, 989 and 1 039 cm(-1). In addition these scattering peaks show an intact crystal shape. The FTIR peaks and Raman spectral peaks shift to higher frequencies showing GE synthetic jadeite jade lacking isomorphism of heavy positive ions.
ABSTRACT
Raman spectrum and X-ray powder diffraction (XRD) were used to study the process andproduct of thermal transformation of nephrite cat's eye from Sichuan province. The results indicate that upon being heated till 900 degrees C, tremolite in the nephrite cat's eye is dehydrated completely and the appearance of a new characteristic band near 671 cm(-1) indicates the form of a new product. At 1 000 degrees C, the intensity of band near 1014 cm(-1) rises obviously, and the weak bands near 573 cm(-1) and 934 cm(-1) present. Up to 1100 degrees C, the band near 1033 cm(-1) appears. All these evidences show that the final thermal transformation product is identified as Ca-Mg pyroxene which is similar to diopside both in structure and in composition. This conclusion is confirmed by XRD.
