what does quartz do?

[ya boi]

It says that its used in the workshop but I don't know where, as when I talk to Eugene it just offers the upgrades that cost ergo and moonstone

[Bullwark]

You need to play through the demo in order to use it. You'll understand when you do.

[ya boi]

ok, I'm currently stuck at the boulevard, the constable puppet there keeps kicking my ass