Geodes can be found by digging blocks throughout the world. There are various different types of Geode and each Geode has a Quality Rating that determines how valuable its contents are.
Geodes can be cracked by talking to G30DE at spawn, or by crafting a Geode Crusher
Stone Geode
Stone Geodes occasionally drop from ores in the overworld. They typically drop Cinnabar, Topaz and Alumite when cracked. They very rarely drop Midnight Diamonds.
Infernal Geode
Infernal Geodes occasionally drop from ores in the Nether. They typically drop Topaz, Hellionite and Nightmare Opals when cracked. They very rarely drop Chaos Stars.
Petrified Burl
Petrified Burls occasionally drop from cutting down trees. They typically drop Amber, Verdant Amber and Ancient Amber when cracked. They very rarely drop Wooden Hearts.
Ritual Stone
Ritual Stones occasionally drop from digging up sand, dirt and gravel. They typically drop Elder’s Jewels, Primeval Tablets and Heretic’s Idols when cracked. They very rarely drop Diviner’s Sceptre’s.