It's a silicon dioxide crystal,
otherwise known as QUARTZ.
The Big Bang Theory Season 12, Episode 2
What do we know
about QUARTZ?
The Big Bang Theory Season 12, Episode 2
Quartz, from the
German "quarz"
The Big Bang Theory Season 12, Episode 2
And that stone in front--
I bet it's QUARTZ.
The Big Bang Theory Season 12, Episode 2
Oh, you forgot your QUARTZ.
The Big Bang Theory Season 7, Episode 13