The Study On Gemology And Mineralogy Of Apatite With Different Colors

Apatite is the most common accessory mineral in igneous rocks.Its chemical formula is Ca₅?PO₄?₃?OH,F,Cl?.It studies the gemology of Lingqiu green apatite in Shanxi Province,light apricot apatite in Anhui Province and gray green apatite in Shaanxi Province.The main instruments used are gem microscope,polarizing microscope,X-ray fluorescence spectrometer,electron probe,LA-ICP-MS,Fourier transform infrared spectrometer,ultraviolet-visible spectrophotometer and micro-Raman spectrometer.It systematically studied the chemical composition and spectral characteristics of apatite of different colours from three producing areas,focused on the indicative significance of trace elements in apatite,and the characteristic significance of spectral characteristics.At the same time,the inclusions from three producing areas were compared and studied.The green apatite in Lingqiu,Shanxi Province is mostly hexagonal column with self-and semi-self-shaped cracks and moderate luminescence;the pale yellow apatite in Anhui Province is slab-shaped,with poor self-shape,weak luster and strong luminescence;the lime green apatite crystal in Shaanxi Province is hexagonal column with high self-shape,poor cleavage and no luminescence under ultraviolet light.XRF results show that the variation coefficients of Ca and P are different.The variation coefficients of apatite in Lingqiu,Anhui and Shaanxi provinces of Shanxi province decrease gradually,and the variation coefficients are positively correlated with LA content.The results of infrared spectroscopy showed that the spectral characteristics of apatite from different habitats were mainly caused by the vibration of[PO₄]^3-in the samples.The infrared absorption peak position of apatite did not shift,and the bending vibration peak V4 had two peaks,and its splitting degree was related to crystallinity.In addition,it is found that the asymmetric angular vibration of[SO₄]^4-can enhance the infrared absorption peak of V4 at 606 cm-1.The results of ultraviolet spectroscopy show that Ce is the main luminescent element of apatite from different color sources.The fluorescence quenching of rare earth elements Ce and Eu occurs at the same concentration.According to the calculation,the molar ratio of phosphorescent elements n?Ce?/n?Eu?of apatite from Shaanxi origin is 1.45,so the samples from Shaanxi Province do not emit light in ultraviolet lamp and Diamondview;the molar ratio of phosphorescent elements n?Ce?/n?Eu?of apatite from Anhui origin is 1.96,and the samples from Anhui Province emit yellow-green fluorescence;the molar ratio of phosphorescent elements n?Ce?/n?Eu?of apatite from Lingqiu origin in Shanxi Province is 12.08,and the samples emit orange-purple fluorescence.Therefore,when n?Ce?/n?Eu?<1.5 in apatite,fluorescence quenching occurs in the interior of gemstone without showing luminescence.At the same time,the ratio of w?Mn?/w?Fe?can also indicate the different effects of elements on luminescence.Lingqiu apatite and Shaanxi apatite w?Mn?/w?Fe?<1,Mn and Fe inhibit the luminescence of apatite,while Anhui apatite w?Mn?/w?Fe?>1,Mn and Fe mainly enhance the luminescence of gemstones.Raman measurements showed that[PO₄]^3-vibration peaks in the three producing areas had little difference.In addition,Raman spectroscopy shows that the main gas component in the gas-liquid inclusions of apatite in Anhui and Shaanxi is CO₂.