Mare basalt regions, especially Mare Tranquillitatis (high-Ti basalts) — ilmenite (FeTiO₃) concentrations up to ~15% by mass
Co-product of oxygen extraction from ilmenite. Iron is structural; titanium is for high-temperature applications. Theoretical use case: in-situ habitat fabrication or local manufacturing for further lunar/Mars infrastructure. Mare Tranquillitatis is high-Ti; Apollo 11 + Apollo 17 returned ilmenite-rich samples. Apollo 17 Camelot crater is a candidate ISRU site.
Lunar iron is for *in-space* use only — terrestrial iron costs ~$0.10/kg; lunar delivery costs are 5+ orders of magnitude higher. Even in-space, fabrication infrastructure (foundries, rolling mills, welding) does not yet exist on the Moon. Iron is a byproduct of O₂ ISRU, not a primary driver.