Romulan mine

Romulan mines in the 22nd century were armed with tricobalt explosives. Upon detonation they produced a thermokinetic explosion equivalent to one quarter of a kiloton. These anti-spacecraft explosive devices, utilized by the Romulan Star Empire, were cloaked with primitive cloaking devices similar to those utilized by the Suliban of the same era, but operating on a different phase variance. The mines were similar in design to triton class spatial torpedoes used by United Earth. The power matrix of the mine used bulky and primitive boridium power cells. 

In 2152, the 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.