Crystalline vertex was a type of valuable dark green gemstone that could be used as currency when cut and placed in the center of gold coins. They could be cut into prism shapes, and were partially transparent.
Behind the scenes
In the new Star Wars canon, crystalline vertex was first introduced in the 2019 reference book Star Wars: How Not to Get Eaten by Ewoks and Other Galactic Survival Skills written by Christian Blauvelt. Within the Star Wars Legends continuity, crystalline vertex first appeared in the 1979 novel Han Solo at Stars' End written by Brian Daley.