Carbothermic reduction of quartz to Si is the overall reaction in Si production. A solid knowledge about the reaction kinetics at high temperature zones of Si furnace will certainly help us to optimize the Si production. In this work, agglomerates made of quartz and silicon as well as quartz and SiC mixtures have been heated in the thermogravimetric furnace at 1550, 1730, and 1820°C in the Ar atmosphere. At temperatures lower than 1550°C, both reactions are slow. At temperatures 1550-1730°C, the Si+SiO2 reacts maximum 1.5 faster than the SiC+SiO2. However, the SiC+SiO2 reaction dominates at around 1800°C. Significant increase of the reaction rate is observed for the SiC+SiO2 with temperatures. The reaction rate increases for 5 times for the Si+SiO2 from 1550°C to 1730°C, while it reduces again at higher temperatures.