Bakterite

Bakterite is a term used in geomicrobiology to describe mineral grains whose formation was mediated by bacteria. It is not a defined mineral with a fixed chemical composition; rather, it refers to biogenic sediment particles that show evidence of microbial involvement in their precipitation.

Mineralogy and texture vary with environment. The most common composition is calcium carbonate (calcite or aragonite), but bakterites can also be rich in silica, phosphates, or iron oxides, depending on available ions and metabolic processes. Textures range from microlaminated sheets to nodular, filamentous, or pore-filling structures that reflect the architecture of the resident microbial community and extracellular polymeric substances that guide mineral growth.

Formation mechanisms involve microbial metabolism that alters local chemistry. Photosynthetic and sulfate-reducing bacteria can raise or lower pH, produce carbonate ions, or provide organic templates for nucleation. Extracellular polymeric substances and cell surfaces often act as nucleation sites, enabling rapid, focused precipitation under conducive conditions.

Occurrences are reported in a range of settings, including microbial mats in shallow seas, caves, hot springs, and freshwater lakes, as well as in fossilizing environments where stromatolite- or thrombolite-like structures form. In the rock record, bakterites can preserve microfossil textures that aid paleoenvironmental interpretations.

Although widely used in scientific literature, bakterite is not a formal mineral designation in major mineral nomenclature databases. It serves as a descriptive term for biogenic precipitates and is of interest for studies of biomineralization, paleoenvironments, and bioremediation.