I met this post from #pypt (which means I'm behind in keeping up with the people I like to keep up with).

Quartz is, of course, used in timekeeping, for reasons I won't even try to purport to understand.

My family and I used to go "gem mining" in North Carolina (which really means digging through pre-salted buckets of dirt with stones in them) and now have a rather heavy collection of some really neat looking stones, many of which are quartz. They can be really colourful!