There are many types of Resources in Wall World, mainly used to upgrade equipment.
Amethyst
Amethyst can be found in all caverns and is used for most upgrades, and is always in high demand.
Diamonds
Diamonds can be found in standard caves. They are used for some advanced upgrades.
Emeralds
Emeralds can only be found in Jungle Caverns. They're mainly used to repair the Robospider, but can also be used in some advanced upgrades.
Obsidian
Obsidian can only be found in Vulcanic caverns. They are used in advanced upgrades, like the Hyper cells.
Hyper cells
Hyper cells can only be found in Flesh Caverns. They are used for advanced powerful upgrades.
Red Quartz
Red Quartz can only be found in Molten Caverns, and used for a few final upgrades.
Bismuth
Bismuth can be found in Refracting Caverns and is used in most upgrade trees.
Processors
Processors can be found Circuit Caverns they're used for a few final upgrades for your equipment.
Relics
Relics are an anomaly that can be found in all caverns and when brought back to the Robospider it unlocks an upgrade tree that only last for the rest of that run. This upgrades are only unlockable by finding this Relics.