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

You can, it would just become a different type of glass. obsidian is considered to be a type of glass and slag from metal refining is also glass like or glass itself. It’s just to get specific properties it requires much more pure ingredients in specific proportions to ensure it has properties such as clarity, strength, colour, etc.