(Need some artwork done, so please help me out)
After escaping on ship to Earth with Tourmaline, Citrine, and Sunstone, Moonstone led the Galactic Gems to a base along with the Sky Gems, and the Ivy Gems. Their base is located under a waterfall in South America. There are three temples, one for each team.
Moonstones from Homeworld were used for the main purposes of guarding Ancient Roman civilizations. The Romans saw the gems as a gift from Artemis, goddess of the moon. When first Moonstone arrived, she and Sunstone were worshiped as Artemis and Apollo.
Moonstone gems are known for being mysterious, and often rebel because of this. She was created under White Diamond to check on the Romans, but instead she hijacked a ship and took several other gems to Earth.