XRD and Morphologic Analysis of α-Cristobalite Produced from Silica Mine Waste under Lower Calcination Temperature

This paper describes a new method developed to produce α-cristobalite from silica mine waste under lower-than-usual temperature, and presents XRD (X-ray diffraction) and morphologic analysis of the produced α-cristobalite. In the method, silica mine waste with average grain volume of 87.3 µm is firstly refined and processed to have a whiteness of 83.5 and a chemical composition of SiO2 of 99.87%, Al2O3 of 0.15%, and Fe2O3 of 0.015% (by weight), before calcinating the processed samples. The experiment results demonstrate that, under oxidizing condition, addition of mineralizer and occurrence of iron oxides as impurity in the mine waste, facilitate lowering both crystallization temperature of amorphous silica and calcination temperature of cristobalite from 1470°C to 1100-1250°C, shortening formation time of cristobalite to 3 hours, raising transformation rate up to 93.7%-99.7%, and increasing whiteness up to 92.3%-96.7%.