Smectite, variety nontronite with bacteria

Dissolution features suggest that, in the absence of oxygen, Fe(III) in clay is used for respiration. Clays and Clay Minerals 51(5), 502-512. DOI: 10.1346/CCMN.2003.0510504).
Dimensions: Field of view approx. 8 microns wide

Hailiang Dong, Miami University, OH. USA