Study On Gemology And Mineralogy Of Changhua Chicken-blood Stone

Chicken-blood stone is a famous and precious carving stone in China, it is praised as"The Queen of Seal Stones"by its gorgeous color and attractive appearance. Changhua Chicken-blood stone is the most famous category of Chicken-blood stone.This paper, based on fieldwork of geology, has done some research on mineralization and alteration, gemology and mineralogy characteristics mainly through using modern testing methods such as observing microscopic sections and analysis of SEM , EMPA , XRD, IR and DTA.Study on mineralization and alteration characteristics of Changhua Chicken-blood stone deposit includes wall rock alteration types, ore characteristics and genesis mechanism. Changhua Chicken-blood deposit attributes to typical post volcanic hydrothermal type, whose mineralization is multistage. Silicification, dickization, cinnabaration, pyritization can be regarded as the important exploration indications to Changhua Chicken-blood because of their intimate association with minerization.Study on mineral composition indicates that the major mineral composition of Changhua Chicken-blood stone is composed of kaolinite group minerals, in which dickite and transitional mineral of kaolinite and dickite occupies most.Micro-morphology observation by SEM examination shows that kaolinite group minerals bear a shape of false hexagonal platy or irregular platy stacking; The HI index has been calculated to testify that the structural order of kaolinite group minerals varies from higher order to lower order; IR indicates that the intensity (A) of 3697 cm-1 band ascribing to outer layer OH vibration is approximately equivalent to the intensity (B) of 3620 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 kaolinite group minerals is between 400～700℃and a strong and sharp exothermic peak appears at 1000°C. There was a positive correlation between the intensity and the order of endothermic vale.Changhua Chicken-blood stone is mainly divided into four categories, which includes"Dongdi","Ruandi","Gangdi"and"Yingdi". The most important factors of Changhua Chicken-blood stone quality evaluation are its color and texture.