Ferromanganese deposits in the caves of the Guadalupe Mountains
— Michael N. Spilde, Diana E. Northrup, and Penelope J. Boston

Cave ferromanganese deposits are an unusual type of mineral deposit present in some caves of the Guadalupe Mountains, NM. These deposits consist of several horizons: a layer of soft, altered “punk rock” underneath a highly colored layer, composed predominantly of Fe, Mn, and Al oxides and hydroxides. The deposits contain a diverse microbial community, and DNA analyses indicate that some identified organisms are closely related to known manganese and iron oxidizers. Originally thought to be derived from chemical corrosion of the cave bedrock, the enrichment of Fe and Mn in these deposits cannot be explained solely by the dissolution of carbonate; Fe and Mn are likely transported from the punk rock zone and enriched in the oxide layer. The accumulation of oxides in one horizon, the breakdown of bedrock in another horizon, and the presence of a microbial community suggests that the deposits are similar to soils and may undergo similar processes.