Study On Near Infrared Spectra Of Common Gemstones

Currently, infrared spectroscopy in gem identification that is mid-infrared multi 400cm-1 ～4000cm-1 range in the fingerprint region, but rarely near-infrared region of the spectrum that is 4000cm-1～10000cm-1 part to do related research. In this paper, Near Infrared Spectroscopy common gem stones and organic characteristics were studied, and the resulting absorption spectra and attribution analysis, increasing the basis for the research and identification of organic gem stones.The results are as follows:1、Gem mineral Near Infrared Spectroscopy widespread presence of water absorption peak, measured in most samples contain water, and is divided into two forms:one is in the form of a water molecule, another form of-OH pure hydroxy. In 5200cm-1 absorption peak of water molecules in a combination of frequency, frequency absorption peak of 7000cm-1 OH characterized. And the water absorption peak position and the presence of water in the form of gemstone minerals, and when only the 7000cm-1 absorption peak described in the gemstone mineral water only in the form of-OH, when 5200,7000cm-1 indicate the presence of both at the same time there are also water molecules -OH exist.2、In addition to the near-infrared region of the spectrum there is a low potential energy of electron transition absorption peak as spessartine to 5898cm-1 and 7849cm-1 as the center of Fe2+ electronic transition is characterized by strong broad absorption band, and only It appears in spessartine in.3、Widespread absorption peak of Si-O bond silicate mineral gem near-infrared spectrum. Nesosilicate zircon presence of silicon-oxygen tetrahedron bending vibration in combination with the hydroxyl stretching vibration frequency 4576cm-1,4830cm-1 located at the silicon-oxygen tetrahedron stretching vibration in combination with the hydroxyl stretching vibration frequency located at 5865cm-1,6025cm-1 place; while topaz and absorption peaks related Si-O group located 4423cm-1 place. Strong garnet with tetrahedral Si-O absorption peak at about 4260cm-1 place.4、An organic gem near-infrared spectroscopy to amino acid frequency, frequency-based combination, in which a combination of stretching vibration 5200cm-1NH amide II frequency (CN stretching vibration, NH bending vibration coupling generated mainly belonging to CN stretching vibration) and 7000cm-1NH stretching vibration is characterized by a multiplier, different varieties of organic gem near-infrared absorption spectrum peak peak, peak, relative intensity differences were all have their own characteristics. It may provide some information for the identification of organic ingredients and organic gem stones.5、Organic filling gem places 4061 cm-1±,4179cm-1±benzene ring=CH stretching vibration and bending vibration frequency combinations and 4620cm-1±,4683cm-1±= CH stretching vibrations of the benzene ring skeleton combination frequency characteristic absorption peak. Wherein the benzene ring absorption peaks is usually indicates that the sample through the fill process. Near-infrared absorption peak Jade A cargo with jade B goods have obvious differences. Jade B goods not only in the near infrared spectrum jade A goods and some water absorption (5238 cm-1 molecule of water stretching vibration and bending vibration frequency combined peak), also shows the benzene ring CH bond vibration absorption peak frequency composition, performance "many peaks" in order to discriminate whether through artificial emerald filling process.