quartz
Quartz is second more common mineral you'll find. Only feldspar is more common. And since most sand is quartz sand, it stands to reason that most sandstone will contain quartz. Despite the very crystalline appearance of quartz, it doesn't have cleavage, and pure quartz does look like glass. It's quite likely as you read this answer that a piece of quartz is within a few feet of you right now. One of its common uses is as a piezoelectric crystal used in creating a stable oscillator used in computers and other devices requiring a cheap, stable, time source.
