From Halopedia, the Halo wiki
K7-49 was discovered by a telemetry probe launched by the prowler UNSC Razor's Edge. Operation: PROMETHEUS was launched against K7-49 on July 27, 2537. The SPARTAN-III Alpha Company disabled enough of the reactors on K7-49 to allow for sufficient cooling and permanently shut down the operation, ruining the Covenant's capacity to produce the metal. Initial resistance to the SPARTANs was light, and after two days, seven reactors had been deactivated before the Covenant organized a proper counterforce. However, the force was neutralized and over the next three days, Alpha Company destroyed 13 more reactors.
However, the Covenant soon arranged a massive counterforce. Unfortunately all 300 of the Spartans were killed in the process. K7-49 was then abandoned by the Covenant. According to Kurt-051, if the operation had failed, the Covenant would have destroyed all of humanity's Orion-side colonies.
K7-49 had a system of artificial volcanic activity created by several high-output plasma reactors. These plasma reactors were used to refine metal used in the construction of Covenant warships. These were then refined, shaped, and shipped away for final assembly. A network of gravity beams then transported refined alloy to the surface to be welded into Covenant battleships.
The name K7-49 contains both the number 7 and its square, 49, another seven reference. Additionally, K is the eleventh letter of the alphabet making the number before the hyphen "117".
List of appearances