A Romulan mine was a dangerous explosive device utilized by the Romulan Star Empire which utilized boridium power cells.
In 2152, the Enterprise NX-01 encountered a field of these mines, which were cloaked, surrounding a planet that the Empire had annexed. The explosion of one such device caused a significant amount of damage to Enterprise's port forequarter. Another mine lodged itself on the hull, dangerously close to the ship's starboard impulse reactor, but failed to detonate. Lieutenant Malcolm Reed and Captain Jonathan Archer attempted to disarm the mine, but were unable to do so before two Romulan Birds-of-Prey arrived, demanding that Enterprise leave the system. Archer and Reed managed to separate the section of hull plating where the mine was attached to the rest of the ship, and detonate the mine at a safe distance from the vessel. (ENT: "Minefield")