Acta crystals were a rare form of currency.

Gowron gave one as a gift to Pok, son of Torghn at his lop'no.

Gowron uncovered the traitor on his ship by using marked Acta crystals to pay his bar tab. (ST novel: Klingon)

Types of currency
materials	acta crystal • gold • latinum • ludugial gold • silver
units	bilbok • cent • credit • darsek • dejebbit • dirak • dollar • drokna • ducat • galorine credit slip • ilec • kern • klon peag • laertian dinar • lek • lita • notch-rock • prime transfer authority • quatloo • sakto • sous • szeket • t'chak • talon • tri-esta