Eureka! I have found it!
California's state motto (Eureka... I have found it!) refers to the discovery of gold in California. The California state motto appears on the state seal, and gold is the official mineral symbol of California.
The Greek word Eureka means "I have found it" (the famed Greek mathematician Archimedes is said to have exclaimed "Eureka!" when he finally discovered a method for determining the purity of gold).