Study On The Mineralogical Characteristics Of Laos Stones

Laos stone is a new kind of seal stone.It is named because it is produced in Asov Province,Laos.It is colorful in color and highly similar in appearance to some kinds of shoushan stone.In this paper,basic gemological tests,Polarizing microscope observation,scanning electron microscope observations,electron probes,X-ray diffraction,infrared spectrom,and Raman spectrom were used to analysis for each color of Laos stone,And the main results were as follows:"Laos stone"mainly includes white,yellow,red,fuchsia,off-white and off-white.Translucent-opaque,waxy luster to grease luster,refractive index 1.56,relative density2.60?2.64.The quality evaluation on the color,texture,transparency,luster,lumpiness and carving process of Laotian stone were carried out respectively.Research on the main mineral structural characteristics shows that there are mainly micro-microlite-aphanitic texture,scaly texture,porphyroblastic texture,allotriomophic porphyritic texture,nervation texture and block mass porphyroblastic palimpsest structures.Scanning electron microscope study showed that the"Laos stone"is mainly in the shape of hexagonal plates,flake,and scaly.kaolinite minerals which crystal was better are in the form of pseudo-hexagonal flake,arranged in imbricate system,some of the crystal faces are more curled,and some of the edges are sharper.They are nonuniform in size,usually 5?15?m,some can reach 30?m.Electronic probe analysis results show that the main chemical components of"Laos stone"are SiO₂ and Al₂O₃ and the content is close to the standard value."Laos stone"also contains trace elements Fe,Cr,Cu,Na,Ca,Al,Si,K,Ti,Cr,P.In addition,the presence of the minor minerals hematite,quartz and rutile have been detected.By analyzing the content of FeO of various colors"Laos stone",the result showed that Fe was responsible for some of the red and yellow and presuming that it was the main cause of"Laos stone"color.Infrared spectrum and X-ray powder diffraction studies have shown The main mineral structure characteristics show that the main mineral composition of Laos stone is kaolinite minerals,mostly dickite and kaolinite,and a small part is dickite-kaolinite,dickite-nacrite or kaolinite-nacrite mixed layer mineral.The crystallinity index HI value of Laos stone was calculated in X-ray diffraction experiment,and the higher the HI was,the better the order degree was.The infrared crystallinity index OI of Laos stone was measured in the infrared spectrum,and it was believed that the lower the transparency of Laos stone with dickite as the main component,the higher the infrared crystallinity index value and the lower the order degree,while the Laos stone with kaolinite as the main component was the opposite.According to the analysis of Raman spectrum,the impurity minerals pyrite,rutile,diaspore,quartz and anatase still exist in the "Laos stone".