Interesting question, ncwine. I was stumped, so I went over to Bruce Sanderson's office (he's Wine Spectator's tasting director) and asked him about iron scents in wine. He said that he associates iron with a mineral flavor. For him, mineral flavors have a few variations; mineral can be more metallic or it can be more salty. Among the regions he tastes most regularly, Bruce often finds iron in the Burgundian regions of Pommard and Nuits-St.-Georges.
After searching years of Wine Spectator tasting notes, I can also tell you that the aroma of iron has been used to describe only red wines and most of them are Cabernet Sauvignons, though it has also been used to describe a handful of Rhone reds. Most of these wines have big tannins and full bodies.
Hope that helps. Has anybody else found the scent of iron in wine?
(And a quick note on terminology. "Taste" refers to the 5 stimuli that affect your taste buds: sweet, tart, bitter, umami and salt. Iron is not one of the five tastes; iron is a scent or an aroma or a flavor. Scents are picked in your nasal passages.)