Red gold is one of the most valuable materials known on Alaria. The metal is a reddish gold that never tarnishes, throws back light better than any polished silver, and weighs noticeably more than common gold for the same volume.
The value is not only in the look of it. Red gold turns aside elemental Kethic the way it turns aside light. A working of fire or light that strikes a polished red-gold surface scatters off it spent and weakened, and a sheet of the metal will blunt a Kethic blow that would have punched clean through steel. That is why it sits among the magical materials rather than the precious ones. A jeweler wants red gold for the color. A Kethic duelist wants it for what it refuses to let through, and so does anyone building a strongroom or guarding a body for a living.
The two properties compound. Because the metal never tarnishes, a red-gold mirror or facing holds its turning-power without upkeep; nothing dulls, nothing wears off, nothing needs renewing. That makes the old pieces as good as the new ones, which is most of what circulates, since red gold is rare enough that very little is freshly mined. Most of what exists has been recut from older work, and a single recovered shield can change hands for the price of a small estate.