Cobalt Mineral is a normal monster that is best known in ExperienceRO for dropping Elemental Sword (100.00%). Only guilds that own the Schwartzvald Guild Dungeon can access its map. However, Cobalt Mineral can also be summoned by Dead Branch.
Note: Cobalt Mineral only has a card in renewal servers. As ExperiencerRO is pre-renewal, the card does not exist. However, you can view the renewal card here.