2
is a need to classify these wastes to understand their chemi-
cal composition, mineralogy, and to evaluate their potential
critical minerals potential.
Acid rock drainage (ARD) occurs in mine waste rock,
tailings, and structures like pits and underground work-
ings. pH levels in mine waste can predict the mobility and
availability of acid drainage. Some critical minerals could
dissolve or leach more readily in acidic or alkaline condi-
tions (EPA, 1993). For instance, certain rare earth elements
(REE) and metals like aluminum and iron are more soluble
in acidic environments. Therefore, understanding the pH
levels in mine waste is important for assessing the potential
release, and migration of critical and other minerals (Plante
et al., 2012 Shu et al., 2001). Paste pH is a straightfor-
ward static test that determines whether stored acidity is
present in mine waste samples (Lapakko 2002, European
Commission 2009), which is used in this study.
STUDY AREAS
Three different deposit types in New Mexico are selected
for this paper to represent three different types of mine
wastes (Figure 2).
Black Hawk District, Grant County
The Black Hawk district is located in Burro Mountains in
southwestern New Mexico (Figure 3) and is one of the few
localities of arsenide five-element veins in the U.S. Arsenide
Figure 1. Periodic table shows critical minerals in New Mexico (revised from McLemore and
Gysi, 2023)
Figure 2. Location of Black Hawk district (Grant County),
Hillsboro district (Sierra County), Magdalena district
(Socorro County)
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