New Mexico Geological Society Annual Spring Meeting — Abstracts

Critical minerals (CMs) are any non-fuel material that has a high risk of supply chain disruption.
The United States is currently importing most of the CMs used in the country, which has led
them to seek alternative sources. Alternative sources for critical minerals include non-traditional
sources such as pre-existing mine wastes. New Mexico has a rich mining history with many
historic deposits of waste rock and tailings, many of which may contain residual critical minerals
that were left behind after the material was processed. For this project, we are using culture-
independent methods to investigate the microbial communities that have developed since these
wastes were emplaced, with the goal of characterizing waste-associated communities and
exploring how microbes might be interacting with the residual minerals in the deposits. Previous
evaluation of microbial communities in historic waste from five mines in three different mining
districts in New Mexico showed that microbial communities vary based on waste type and
geochemistry; however, the high proportion of unclassified microorganisms limited any
inferences about microbial biogeochemistry (Best et al., 2025). Therefore, in this work, we are
expanding our investigations to five new locations throughout New Mexico to represent more
diverse regions and waste types, including tailings and waste rock from carbonate-hosted
deposits. Our methods include a combination of cell counts, rRNA gene and transcript
sequencing, whole rock geochemistry, and metagenomics to expand on the previous work by
Best et al. (2025), and explore the genomic potential of novel populations in these wastes. rRNA
gene libraries from the new deposits show that they contain diverse Actinobacteriota, Alpha-,
and Gammaproteobacteria, as well as archaeal populations such as unclassified
Nitrososphaeraceae and “Candidatus Nitrososphaera.” Low coverage metagenomic libraries
contain genes for carbon fixation, but there is little evidence for inorganic sulfur or iron oxidation.
However, we recently obtained deeper metagenomic datasets, which may reveal more about
the dominant microbial populations and the metabolic potential of the communities overall. We
will present results from these new rRNA gene and metagenomic libraries and discuss the
implications for the biogeochemistry of legacy mine waste and possible microbial approaches to
critical mineral recovery.

Best MB, Kazemi Motlagh Z, McLemore VT, Jones DS. 2025. Historic mine waste contains diverse microbial
communities that reflect waste type and geochemistry. Appl Environ Microbiol 91:e00434-25.
https://doi.org/10.1128/aem.00434-25

References:

1. Best MB, Kazemi Motlagh Z, McLemore VT, Jones DS. 2025. Historic mine waste contains diverse microbial
   communities that reflect waste type and geochemistry. Appl Environ Microbiol 91:e00434-25.
   https://doi.org/10.1128/aem.00434-25