| Primary deposit of“Chicken-blood jade”is located in the Dadi-Sanmen-Jizhao area of Longsheng County,Guilin City,Guangxi.It occurs in the shallow metamorphic marine volcanic rock series of the Sanmenjie Formation of the Upper Proterozoic Danzhou Group.In this paper,the Gemological properties,chromogenic origin and structural characteristics of“Chicken-blood jade”were studied by hand specimen observation,polarizing microscope observation,electron probe,scanning electron microscopy,X-ray diffractometry,X-ray fluorescence spectrometer,micro-Raman spectroscopy,infrared spectroscopy and ultraviolet spectroscopy.Because the name of“Chicken-blood jade”has been included in the national standard,quotation marks are omitted below.The main mineral components of Chicken-blood jade are alpha-quartz,and the secondary minerals are hematite,magnetite,dolomite,pyrite,chlorite,talc,apatite,calcite,etc.Dolomite and talc will reduce the hardness of chicken blood jade,and dolomite will also reduce its transparency.The size of quartz matrix is generally about100?m.Hematite is densely distributed among quartz grains in dot-like,dot-dusty and scaly shape.There is metasomatic magnetite phenomenon.Pyrite is mostly semi-automorphic and heteromorphic.Under scanning electron microscopy,quartz can be accumulated in spherical or lamellar shape,and iron oxides are scattered or clustered.The crystallinity index of Chicken-blood jade is between 7.6 and 9.8,which indicates that it has good crystallinity.Infrared transmission spectra of Chicken-blood jade showed consistent quartz peaks at 1165,1080,795,777,692 and 459 cm-1,1618 cm-1 is the bending vibration peak of water and 3464 cm-1 is the stretching vibration peak of water.The first-order ultraviolet-visible-near infrared spectra of Chicken-blood jade are correlated with color.The main absorption peaks of yellow are 450,590,765 and 734 nm,the main absorption peaks of red are 618 and 745 nm,and the absorption of pink is obviously different from that of red at 200-500 nm.The first derivative spectra of red Chicken-blood jade mainly have 584 and 700 nm characteristic peaks,indicating the existence of hematite;the main peak of the first derivative spectra of yellow Chicken-blood jade is 547 nm,accompanied by 435 and 385 nm secondary peaks,indicating the existence of goethite.Raman spectroscopy detected 298 and 398 cm-1 characteristic peaks of goethite and 222,240,289,404,498,615 and 1318 cm-1 characteristic peaks of hematite.XRF surface scan showed that Fe and Mn elements were correlated with red color,and the content of Fe was proportional to red saturation.Ni is enriched in the white area and red is rare.Hematite makes Chicken-blood jade red,goethite makes Chicken-blood jade yellow,chlorite makesChicken-blood jadegreen,hematite and magnetite make Chicken-blood jade black. |
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