Study on mineralogy characteristics of diamond from Shengli No.1 rock pipe in Mengyin County, Shandong Province

Mengyin County, Shandong Province is one of the important diamond producing areas in China, with significant reserves.On the basis of previous studies, this paper studies the mineralogy, spectral characteristics, chemical composition of inclusions and geological origin of diamonds in Shengli No.1 rock pipe in this area using conventional gemological testing methods, infrared spectrum analysis and electron probe analysis.The results show that the diamonds in this area are of equiaxed crystal system, with strong diamond luster, mainly light brown in color, and mainly rhombic dodecahedron and octahedron in crystal form.The common etching images of crystal surface mainly include inverted triangle pit, imbricate etching image, disk etching image, and the internal inclusions are mostly black solid forms.The infrared spectrum indicates that the main types of diamonds are IaA and IaAB, followed by a small number of IaB and II types.The electron probe results indicate that the main components of the inclusion are Na₂O, MgO, Al₂O₃, K₂O, CuO, and SiO₂.The other trace elements include Cr, F.The results speculate that the inclusions are highly likely to be rock salt, potassium salt, and copper salt, and also indicate the involvement of alkali metals in the formation of diamond in Shandong Province.