Gemmological Characteristics of Nanhong Agate

Nanhong agate is studied by using conventional gemmological tests，EDXRF and infrared spectrometer to summarize gemmological characteristics and identification methods.The regular inspection result shows that gemmological characteristics of Nanhong agate are basically similar to those of chalcedony，with only some unique features，such as obvious colloid feeling and red particle structure.Many red particles can be observed in the colour of semitransparent parts by magnification，and it can’t be observed in the red and opaque Nanhong agate samples.EDXRF result shows that the main chemical composition of Nanhong agate is Si with microelectronics such as Fe，K，Ca，Ti，Zn，Cr，etc.It can be concluded that the trivalent Fe^3＋contributes to red colour of Nanhong agate，and red particles of red semitransparent parts are composed of Fe₂O₃.In addition，it can be seen that the bright degree of red part is directly proportional to the content of Fe.The results show that infrared spectra of Nanhong agate match well with those of chalcedony and quartz，which reveal that Nanhong agate is transitional phase from quartz to chalcedony agate with the texture between cryptocrystalline and phanerocrystalline.