eli5: Why does sand which is a bunch of tiny rocks, turn into glass, but we can’t turn big rocks into glass?

Question

I’m very tired. Please help me understand this.

In: Other

Answer 1

Rocks consist of lots of different minerals, most of which don’t make good glass. Sand consists mainly of quartz, which does make good glass. And not all sand will work: Glass makers need to find sand that’s almost pure quartz, and filter out the other stuff.