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

In general you can.

It just doesn’t make very nice or useful glass as most big rocks are made of the wrong stuff.

And the big rocks made of the right stuff to give us good glass are harder to melt and deal with due to size. So it’s easier to use the tiny rocks of the good stuff in the right type of sand than to try using bigger rocks.