Smectites are clay minerals that can contain large amounts of structural iron. Unlike iron oxides, they do not dissolve when their iron is reduced, so they can be reduced and reoxidized many times. This makes them a recyclable pool of redox-active iron that supports microbial respiration, trans...
Source: [Phys.org](https://phys.org/news/2026-10-tetrahedral-iron-clays-exchange-electrons.html)