Abstract: Crystalline magnesium silicates are synthesized from silica-containing brines, preferably spent geothermal brines, by mixing the brine with a magnesium-containing compound, adjusting the pH of the resultant mixture between 8.0 and 14, and crystallizing the magnesium silicate from the mixture at a temperature between 50° C. and 200° C. Kerolite is preferably synthesized from brine by adjusting the pH in a range between 9.5 and 10.5 and heating the mixture to between 100° C. and 170° C. to precipitate the crystalline kerolite. The brine remaining after the crystallization step is depleted in silica and can be further processed without significant problems caused by silica scaling.