Black Rock Quarry Hidden Location. For this location Jessie will have to reach the ledges by flying and jumping. Go through the woods and head to the door leading to the Blackrock Quarry.
Continue until you reach the next elevator leading this time to the excavation site. Then head downwards and be mindful of mold enemies. Hidden Location 8 Transit Corridor South 406 Look for an office window up along the wall.
In the Black Rock Quarry Entrance where the Astral monster is is a door in an above alcove you can enter.
In the room just past the Black Quarry Entrance Control Point the one where all the monsters and Hiss attack you is a doorway located above everything to the left. Continue until you reach the next elevator leading this time to the excavation site. In the hidden location on the 5th floor of the Panopticon to the left of the Swan Altered Item. It is an abandoned quarry.