The solubility of silicon dioxide, SiO2, in water depends on a number of different factors, including pressure, temperature and the structure of its surface. Generally speaking, silicon dioxide is virtually insoluble in water at room temperature.
The solubility of silicon dioxide increases with higher pressure or temperatures, with the level of solubility increasing dramatically above 100 degrees Fahrenheit. When silicon dioxide dissolves in water, the reaction forms silicilic acid.
There are more than 13 distinct structural modifications of silicon dioxide, each of which has its own level of solubility. For instance, macrocrystalline quartz is much less soluble than either chalcedony or amorphous quartz glass.