Study On Gemology And Mineralogy Of Balin Stone

Balin stone,as one of"Four Famous Seal stones of China", with sleek texture, peculiar grain, gorgeous color and various category, is becoming a superior stone preferred by the sculptors and collectors , and increasingly well-known at home and abroad.This paper, based on fieldwork of geology, has done some research on mineralization and alteration, mineralogy and gemology characteristics mainly through using modern testing methods such as observing microscopic sections and analysis of EMPA, XRD, SEM, IR and DTA, in order to make study on Balin Stone more systematic, scientific and perfect.Study on mineralization and alteration characteristics of Balin Stone deposit includes surrounding rock alteration types, mineralization stages, ore characteristics and genesis mechanism. Balin Stone deposit attributes to low-temperature hydrothermal alteration type, whose mineralization is associated with post volcanic hydrothermal fluid with multi-periodic activities, and mainly divided into four mineralizing periods, which is surrounding rock alteration, hydrothermal metasomatism, altered superimposition and cinnabaration. Silicification, alunitization, kaolinization, dickization, pyritization, pyrophylitization, cinnabaration can be regarded as the important exploration indications to Balin Stone because of their intimate association with minerization.Study on mineral composition indicates that the major mineral composition of Balin Stone is composed of kaolinite group minerals, in which transitional mineral of kaolinite and dickite occupies most. Micro-morphology observation by SEM examination shows that kaolinite group minerals bear a shape of squama, fause hexagonal platy or platy stacking; XRD shows that there coexist the characteristic diffraction peaks of kaolinite and dickite. The HI index has been calculated to testify that the structural order of transitional mineral of kaolinite and dickite varies from higher order to lower order; IR indicates that the intensity (A) of 3688 cm-1 band ascribing to outer layer OH vibration is approximately equivalent to the intensity (B) of 3615 cm-1 ascribing to inner layer OH vibration, and the value of A/B becomes relatively lower when the HL index is higher; DTA curve shows that the dehydroxylation temperature of transitional mineral of kaolinte and dickite is near to dickite, with a endothermic vale of different depth at 660°C and a strong and sharp exothermic peak at 1000°C. There was a positive correlation between the intensity and the order of endothermic vale.Balin Stone is mainly divided into four categories, which includes Chicken-blood Stone, Fuhuang Stone, Lardite and Colorful Stone. The paper also summarizes the evaluation factors and grade division about different categories.