Silica (Si02) is often blended with other compounds for coloring or other purposes. In order to obtain highly pure silica (fused quartz for lenses or other optical purposes), these sources must be purified.
This explanation is a rehash of Extraction of silicon dioxide from waste colored glasses by alkali fusion using potassium hydroxide by Mori, H. From the Journal of Materials Science, Volume 38, Number 16, 15 August 2003 , pp. 3461-3468
Silica reacts with molten potassium hydroxide at 300 degrees Celsius. Once cooled, a dissolvable powder remains. Highly pure Silica precipitates from a solution of this powder upon neutralization with acid. Iron and other impurities remain in the solution and may be reclaimed by other means.
The author claims that this process results in a silica hydroxide salt (Si(OH-)4 K+4), though I have found no confirmation that such a compound exists, nor does the author explain how the presence of such a compound was determined. If silica hydroxide does result, processes similar to this may be used to create oligomers (monomer and dimer aluminosilicate hydroxides) for Geopolymers.