As for back as the 2310's, General Mining Corporation was a major mining company. Over time, it managed to knock most other companies out of business, though some of these came together as Combined Arms Mining Company, an attempted "rival". Despite Combined Arms attempt to fight back, General Mining continued to grow.
After the Human-Covenant War, Combined Arms did manage a comeback, but General Mining kept an edge through the use of advanced mining machines capable of independently mining and digging out valuable minerals. It is currently the largest producer of Titanium and the largest stake holder in the Dust mining conglomerate.