Checking wikipedia, it looks like silica-based sands are the most common type. Most rocks are composed heavily from silicate compounds -- I'm guessing this is why sand manufacturing is possible. Calcium carbonate, which is crushed coral and shellfish, is the second most common type of sand.
I'm curious about the differences between these two types of sand and how it affects their use cases. I also wonder if manufactured silica-based sands are any different from the naturally occurring variety.
