[Spectroscopy Identification of Untreated and Heated Corundum].

Nowadays, a great quantity of heat treating corundums are emerging in our market. It is hard to distinguish them scientifically just by conventional methods. In order to accurately determine whether the corundums have been heated or not, we need to analyse their spectral characteristics. This paper describes the spectroscopy identification of untreated and heated corundum. The experiment is conducted as follows: First, We observed the inclusions of corundum samples, then measured and recorded their infrared spectra, UV-Vis spectra by Fourier Transform Infrared Spectrometer and Ultraviolet-visible Spectrophotometer respectively. Next we chose a part of samples to heat, after the heat treatment, we recorded their spectra and made a comparison with that of untreated corundums. The results showed that we can detect the absorption peaks at 1 980 and 2 110 cm(-1) which represent diaspore in untreated ruby. However, after heat treatment, the absorption peaks disappear which means the structure of AlO(OH) has been destroyed. The sapphires which grown in alkali basalt under reductive condition appear the absorption peak at 3 310 cm(-1). However, this peak vanishes after 18 h heat treatment when the temperature is 1 600 ℃. For UV-Vis spectra of ruby, after heat treatment, the slight shift occurs in strong, wide absorption band at around 555 nm, and this band becomes more pointed. In addition, absorption intensity difference between wave crest and wave hollow increases. The absorption bands at 375, 387, 454 nm of heated sapphires are more pointed than that of the untreated sapphires, and absorption intensity difference rises. These changes in spectral characteristics can help us to distinguish untreated corundum from heat treating corundum.

[The Gemological Characteristics of One Kind Turquoise Imitation].

It has been a long time that the imitations of turquoise appear in gem market. Pressed dyed carbonate in the early stage and dyed variscite, chalcedony as well as magnesite appeared in succession. These kinds of materials do not have the color and characteristics of natural turquoise. Their physical and optical properties are quite different from natural turquoise. One kind of turquoise imitation newly appears in market is selected to be studied in this paper. The conventional gemological method, infrared absorption spectroscopy and X-ray diffraction were employed to study its mineral compositions, gemological properties and structural characteristics. The results show that: the brecciated structure can be observed and the distribution of the iron wire is very simple on the surface of the sample. Deep blue granules are visible on the surface of blue samples and a few black spots can be observed on the surface of white ones, which are typical indication of pressing process. The blue imitations of turquoise has been stained and pressed. The index of this kind of turquoise imitation range from 1.54 to 1.58, which is lower than that of natural turquoise and it show bluish white fluorescence, which can be used as important evidence to distinguish it with natural turquoise. The data of X-ray diffraction shows the sample mainly consists of enstatite and quartz. The results of infrared absorption spectroscopy show that the absorption spectra of this kind of turquoise imitation is in accordance with the typical absorption peaks of enstatite: the absorption peaks which locates near 1 088 and 799 cm-1 are associated with Si­O, Si­O­Si stretching vibration in quartz; the absorption peaks near 2 947 and 2 882 cm-1 is related with stretching vibration of CH2 of exotic organic resin; the absorption peaks near 1 736 and 1 510 cm-1 are resulted from the bending and stretching vibration of CO and CH2.

[Vibrational spectra of Caesious nephrite from Qinghai Province].

Qinghai caesious nephrite is discovered in the 1990s in the Golmud area of Qinghai Province. The conventional gemological testing methods, electron microprobe, infrared absorption spectroscopy and Raman spectroscopy were used in this study to analyze the chemical composition and infrared spectra characteristics of the caesious nephrite, selected from the jade mine of Xiaozhaohuo river in Golmud area. The results show that, the gemological physical properties of the Qinghai caesious nephrite are similar to other origin nephrite. Electron microprobe analysis indicates that the MgO, CaO and SiO2 are the major and stable composition for the caesious nephrite. The content of MgO and CaO are 18. 572%-23.603% and 12.333%-12.807% respectively. Moreover, the content of SiO2 is 56.799%-59.926%. In addition, it also contains a higher content of FeOr(Wt%: 1.924%-8.699%) and an amount of Al2O3, TiO2 and Na2O. Infrared absorption and Raman spectra show that the Qinghai caesious nephrite has a characteristic spectral features of tremolite indicating it is mainly composed of tremolite. The different frequency of the infrared absorption bands is due to the difference of Mg--Fe2+ isomorphous substitutionand Fe2+ content of the caesious nephrite. Comprehensive analysis of chemical composition and vibrational spectroscopy indicate that the color of dark gray blue for the Qinghai nephrite is mainly related to its high content of FeOr, and the Fe is a main coloring element.

[Spectroscopic characteristics study of morganite from Mozambique].

In recent years, morganite is becoming more and more popular due to its special color. The morganite samples located in the Republic of Mozambique were detailedly analyzed for its basic properties, chemical composition characteristics and spectroscopy properties by laser ablation plasma mass spectrometry (LA-ICP-MS), ultraviolet-visible absorption spectra (UV-Vis-NIR), infrared spectrum (IR) and Raman spectroscopy. The color parameters of morganite samples including the main wave- length, saturation, and lightness were got by UV-Vis-NIR Chemical composition test showed higher content of Li, Rb, Cs and Mn in samples and chemical formula was calculated as Be3.2090 Al2.0757 Li0.425 Si5.664 O18 (Na0.1420 Cs0.1316). Infrared spectroscopy showed that morganite structure vibration area is mainly in the fingerprint area 400-1200 and 900-1200 cm(-1) for the vibration of the ring Si--O--Si, 550-900 cm(-1) for Be-O vibration area, and 450-530 cm(-1) for Al--O vibration area. Because the Cs element content is higher in sample morganite and Cs belongs to higher atomic number elements, its existence may move the vibrationfrequency of Si--O--Si rings to the low position. Raman spectra showed 1065 cm(-1) for Si-O inner vibration of non bridge oxygen, around 1000 cm(-1) for Be--O outer vibration of non bridge oxygen, 685 cm(-1) for Si--O--Si inner vibration of deformation, 400 cm(-1) for O--Be--O outer vibration of bending, 390 cm(-1) for. Al--O outer vibration of deformation, 320 cm(-1) for Al--O outer vibration of bending.

[The spectrum characteristic analysis of mammoth ivory].

Due to the similarities between mammoth ivory ornaments and modern elephant ivory ones in the market, the spectral properties of the two kinds of ivories were analyzed and compared in the present paper through the gemological tests, infrared spectrum and X-ray powder diffraction, etc. The research found that the refractive index and specific gravity of the two ivories are very similar. The refractive index of mammoth ivory is 1.52-1.53 whereas that of elephant ivory is 1.54-1.55. The specific gravity of mammoth ivory is 1.77 and that of elephant ivory is 1.72. It should be careful that Schreger angles are used to distinguish the two kinds of ivories, because the angles of inner and middle layers in the two kinds of tusks are similar except the angles of elephant tusk out-layers are larger than those of mammoth (The Schreger angle of the sample mammoth ivory belonging to out-layer tusks is 100 degrees nd that of elephant ivory is 115 degrees). In addition, the out-layer Schreger angles of Asian elephants are normally less than 120 degrees, while those of Africa elephants are bigger than 120 degrees (This can be used to identify Asian and Africa elephant ivories). The infrared spectroscopy test shows that the water-molecule-related absorption peaks of 3319, 1642 and 1557 cm(-1) are more obvious in the modern elephant ivory samples than in the mammoth ivory samples; the collagen-related absorption peaks of 2927and 2855 cm(-1) are obvious in the modern elephant ivory but extremely weak in the mammoth ivory. The results indicate that collagen and crystallized water in mammoth ivory reduced to a very low level after having been buried for a long period. X-ray powder diffraction results show that the diffraction peak splits of mammoth ivories are more obvious and sharp than that of elephant ivories, which means hydroxyapatites crystallized better despite being buried for thousands of years. Hence, it is an important reference for identifying the two kinds of ivories that the ivory organic matter was losing and inorganic matter crystallized better at same time after having been buried.

[Mineralogical and spectral characteristics of copper pectolite].

Copper pectolite, a type of pectolite with blue stripes, is a rare gem material with a great market prospect. Mineralogy and genesis were investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), Raman spectroscopy (Raman), scanning electron microscopes (SEM) and ultraviolet-visible spectrometer(UV-VIS) to understand the mineralogical compositions and characteristics of the parts with different color. XRD, FTIR and Raman result showed that copper pectolite is composed of pectolite and minor calcite, consistent with the result of SEM. FTIR showed that an obvious band at 1 500 cm(-1) with 883 and 710 cm(-1) occurred on the white part that contain minor calcite, while the band was absent on the blue part. UV-Vis absorption spectroscopy analysis showed that the blue part has 640 nm absorption band in the UV area that indicates containing elements Cu. The different mineralogical compositions of the white and blue part indicate their different geological conditions.

[Study on the vibrational spectra characterization of the "she tai cui" jade].

The gemological testing methods, infrared absorption spectrum, Raman spectrum and X-ray powder diffraction were employed to study the gemological characteristics, spectral characteristics and structural features of the "She tai cui" jade. It is indicated that most "She tai cui" jade has the refractive index in the range of 1.53 to 1.54, and a density of 2.65-2.79 cm(-1), and the hardness of 6.5 to 7 in addition to the low hardness (< 5) for the pure white one. The mineral constitution is dominated by quartz in most of the "She tai cui" jade, except the white one, which is dominated by dolomite (about 63.91%). The former may contain a certain amount of other impure minerals and is attributed to the quartzite jade, while the latter contains a certain amount of SiO2 (about 34.85%) and a trace amount of calcite and albite, and is attributed to the dolomite jade.

[Gemology and spectra characterization of gem garnet from Muling City, Heilongjiang Province].

Cenozoic basalts gem-garnets from Muling City, Heilongjiang Province were studied by using standard gemological methods, electron microprobe, Raman spectroscopy, infrared spectroscopy, and ultraviolet-visible spectroscopy to obtain the gemology and spectra characterization. Chemical composition analysis indicates that the garnets are pyropes with some impurity element Fe, Ca, Mn, Cr, and Ti. The average chemical structure formula of the gem-garnet is (Mn0.022 Ca0.455, Fe(2+)0.720, Mg1.793) sigma = 2.990 (Ti0.003 Cr0.009 Fe(3+)0.062 Al1.951) sigma = 2.025 (SiO4)3. Roman spectrum analysis suggests that there are mixed-phases in the garnet, which can be shown by the Roman shift which is caused by bridging oxygen vibration of garnet. The Roman shifts of bridging oxygen bending vibration of pyrope are at 560 cm(-1) (A(1g)), and 641 cm(-1) (E(g) + F(2g)), while the Roman shifts of bridging oxygen bending vibration caused by E(g) + F(2g) of almandine and grossular are at 507 and 486 cm(-1). IR functional group area indicates that the pyropes have no molecules water, but seldom pyropes have a little structure water, which forms three stepped weak absorption peaks at 3 585, 3 566 and 3 544 cm(-1) respectively. Most pyropes are brown-red, which is caused by electronic transitions of impurity ions Cr3+, Fe3+ and Mn2+. UV-Vis spectra show that absorption peaks caused by electron transition of Fe3+ are at 570, 521 and 502 nm, while absorption peaks caused by electron transition of Mn2+ are at 460 and 430 nm, and absorption peaks caused by electron transition of Cr3+ are at 690 and 367 nm.

[Study on XRD and infrared spectroscopy of nephrites from Xinjiang and Xiuyan, Liaoning].

The nephrite species with different colors from Xinjiang and Xiuyan, Liaoning, including gray nephrite, yellow nephrite, white nephrite, jasper and He-Mo nephrite, a special nephrite from Xiuyan, were selected for the present study. The gemological testing method, infrared absorption spectroscopy and X-ray powder diffraction were used to analyze and compare the gemological characteristics of the nephrite with different colors and textures from the above localities, in order to understand the similarities and differences between these nephrites with similar colors but different origin, and provide a theoretical basis for the identification of the nephrite origin. The results show that the nephrites from Xinjiang and Xiuyan, Liaoning province have similar gemological properties. They have similar refractive index of 1.60-1.62 and density of 2.660-3.020 g x cm(-3), and only the density has some differences with different colors. The fluorescence.characteristics are not obvious in these nephrites. The major constituent minerals for these nephrites are tremolite, and small amounts of clay minerals such as chlorite and illite are found in the jasper from Xinjiang. Based on the X-ray powder diffraction analysis on the different types of nephrite from two localities, it was shown that the character of spectra peaks and diffraction intensity of different types of nephrite can reflect the texture of the nephrite and the size of crystalline particles to some extent. The infrared absorption spectra are similar for the nephrites from two localities. The infrared absorption spectrum does not make sense to identify the origin and species of nephrites.

[Raman spectroscopy study on the mineral composition of the Guatemalan jade].

Guatemala is another jade commercial origin in addition to the Myanmar. The Guatemalan jade is usually an assemblage of a variety of mineral compositions, and the mineral composition is unique and different from the Myanmar jade. The characteristics of the structures and paragenetic minerals of the purple and gray-green jade from Guatemala were studied by laser Raman spectroscopy analysis. The results show that the jadeite is a major constituent mineral in Guatemala jade, associated by a variety of coexisting minerals. The paragenetic minerals in Guatemalan jade can be divided into five categories, including the dark minerals hornblende, dolomite, omphacite, chlorite, and light-colored mineral apatite. The hornblende, dolomite, omphacite and chlorite are also the paragenetic minerals in the Myanmar jade, but the apatite is almost invisible in the Myanmar jadeite.

[Infrared spectroscopy and XRD studies of coral fossils].

Coral fossil is an old remain of multicellular animal on the earth, and formed by various geological processes. The structural characteristics and compositions of the coral fossils with different color and radial texture on the surface were studied by infrared absorption spectroscopy and X-ray powder diffraction analyses. The results show that the studied coral fossils mainly are composed of SiO2, and the radial microstructure characterized by the calcareous coral cross-section is preserved. It is formed by metasomatism by SiO2. The infrared absorption spectra of the coral fossil with different color and texture are essentially the same, showing typical infrared absorption spectra of the quartz jade. XRD analysis shows that the main components of the coral fossils with different color and texture are consistent and mainly composed of SiO2 with a trace amount of other minerals and without CaCO3.