Analysis of the Composition and Microstructure of Coral Fossil

Coral fossil is formed by various geological effects while buried under the ground for a long time. Current research on coral fossils is focused mainly on the geological and biological evolution of the coral fossils, but less on their components and microstructure. X-ray Diffraction (XRD), Differential Thermal Analysis (DTA), Thermo-gravimetric Analysis (TG) and Scanning Electron Microscope (SEM) and other methods were conducted to determine composition, content and microstructure characteristics of coral fossil samples collected from Shanxi province. The results show that the coral fossils from Shanxi province are composed mainly of calcium carbonate (CaCO₃), and the average content is as high as 98.6%. Phase transition of coral fossils occurred at 700℃ with a sharp decline in the mass, namely the CaCO₃ decomposed to CaO and CO₂. The internal structure of Coral fossils showed a large number of pores whose size is 1-5 μm. Fracture morphology is the same as cleavage fracture, corresponding with 'river pattern'. Coral fossil storage and processing methods to avoid acidic substances and high temperature are described. The highest temperature is 650℃. It is important to avoid a cleavage plane or make an angle between a facet and cleavage plane during processing.