Spectroscopic Analysis and Origin Characteristic of Purple Duanxi Inkstone

Samples of the purple varieties of Duanxi inkstone: Laokeng, Kengzaiyan, Mazikeng, and Songkeng were studied using test instruments including electron balance, polarizing microscope, infrared absorption spectroscopy, and Raman spectroscopy to reveal their mineral components, gemmological characteristics and vibrational spectroscopic features. The results show that the samples of the four varieties of Duanxi inkstone are of chalky-muddy structure with massive structure. The density ranges from 2.68 to 2.83 g/cm³, hardness 3-4, dense structure and good toughness. The colour is dominated by purple, and the polished surface is mostly earthy luster. Infrared spectroscopy and Raman spectroscopy test results show that the four varieties of Duanxi inkstone samples have similarity in the main constituent mineral species, mainly composed of quartz, sericite and rutile, while the impurity minerals are chlorite, monazite, rhodochrosite and other manganese ore. Among them, the Songkeng samples contain more quartz and have a lower relative density than the other three varieties of samples. The presence of quartz in the Duanxi inkstone promotes its abrasive properties, while the presence of minerals such as chlorite and mica makes it excellent for ink storage. Through the preliminary comparison of conventional gemmological features, infrared absorption spectroscopy and XRD, the four varieties of purple Duanxi inkstone and purple Taoyan samples can be distinguished by their appearances and mineral components.