Glass is made of sand, which is a kind of rock. But glass is transparent. We explore why! Glass is made of sand, which is a kind of rock. But glass is transparent, and rocks aren’t transparent. What’s ...

(via It's Okay to Be Smart) Glass is made of sand, which is a kind of rock. But glass is transparent, and rocks aren’t transparent. What’s up with that? Why is glass clear? And why can I sit on a ...

The best way to understand glass is to understand how it is made. The first step to make glass requires heating up a mixture of minerals – often soda ash, limestone and quartz sand – until they melt ...