high Temperature and Pressure with a large silicate source.
The most likely source would be another sedimentary rock, especially another sandstone. While metamorphic and igneous rock usually contain quartz (though not always) they also contain other minerals such as feldspar that may be included in the sandstone. If a sandstone is reworked, with its grains eventually incorporated into another sandstone, in the process the grains of any other mineral are usually weathered to such a point that they essentially are absent from the new sandstone. As for volcanic rock - actually a type of igneous rock - it seldom would have visible grains of quartz in the first place!
