The Gunpowder Mines are the first floor of the Deep Caverns. They are accessed by simply walking straight into the mouth of the cave when first arriving at the Deep Caverns.
If you continue going downwards from this area you will arrive at the Lapis Quarry.
The following Ores can be mined in this area:
In this area, aggressive Sneaky Creepers will randomly spawn and try to attack players.
They are Level 3 and spawn with 120 HP. They typically like to spawn behind players, to attack them off-guard.
Sneaky Creepers are the player's main source of Gunpowder.