What currency did they use or even mention in the book?

I’m looking to run a roleplaying game set in the Cinderspire world and I’ve been taking notes from the book.

They talk about different kinds of crystals and what they do.

It clearly differentiates power crystals (who do things like generate a shroud, power lift crystals, power etheric web) but it doesn’t seem like you need a power crystal for lumen crystals or weapon crystals (since they are gauntlet mounted).

Is this accurate? How do you think the cannon crystals are activated? And can lumen crystals be turned on and off?

Thanks for any assistance.