Magnesiothermic methods of producing solid silicon are provided. In a first embodiment, solid silica and magnesium gas are reacted at a temperature from 400° C. to 1000° C. to produce solid silicon and solid magnesium oxide, the silicon having a purity from 98.0 to 99.9999%. The silicon is separated from the magnesium oxide using an electrostatic technology. In a second embodiment, the solid silicon is reacted with magnesium gas to produce solid magnesium silicide. The magnesium silicide is contacted with hydrogen chloride gas or hydrochloric acid to produce silane gas. The silane gas is thermally decomposed to produce solid silicon and hydrogen gas, the silicon having a purity of at least 99.9999%. The solid silicon and hydrogen gas are separated into two processing streams. The hydrogen gas is recycled for reaction with chlorine gas to produce hydrogen chloride gas.