1
24-042
Geochemistry of Critical Minerals in Mine Wastes at Hillsboro
and Steeple Rock Districts, New Mexico
Abena S. Acheampong-Mensah
New Mexico Institute of Mining and Technology,
Socorro, NM
Virginia T. McLemore
New Mexico Bureau of Geology and Mineral
Resources, Socorro, NM.
ABSTRACT
Critical mineral endowment of mine wastes in two min-
ing districts in New Mexico (Copper Flat at Hillsboro and
Carlisle-Center mines in the Steeple Rock district) will be
characterized and estimated. “Beta-testing” of USGS pro-
cedures was performed. Potential critical minerals at these
deposits include As, Bi, Te, Zn, Co, Ni, Mg, Mn, and fluo-
rite. pH and particle size of samples were analyzed to deter-
mine weathering and migration potential of heavy metals.
Soil pH was also measured to determine the potential for
Acid Rock Drainage. The pH of the waste rock piles ranged
from 3.66 to 5.67 which indicates fine- grained pyrite or
sulfide oxidation. The samples collected from the tailings
however, showed a different range of pH, from 6.30 to 8.62,
probably due to the presence of carbonates. Difference in
particle size fractions and its distribution along the slope are
generally influenced by natural occurrences (e.g., gravity
and pre-mining hydrothermal alteration) and operational
activities such as material piling or dumping. Future work
includes analyses of mineralogy and particle size correla-
tion and estimation of critical mineral endowment of these
mine wastes at New Mexico.
INTRODUCTION
According to the Energy Act of 2020, a critical mineral is
a non-fuel mineral or mineral resource that is crucial to
the U.S.’s economic and national security with a poten-
tial disruption in its supply. Most of our electronic equip-
ment, such as smartphones, laptops, computer chips, wind
turbines, hybrid, and electric cars, etc., depend on these
rare earth elements (REE) and other critical minerals. This
coupled with the anticipated rise in demand for critical
minerals and the potential shortage of production capac-
ity from China and other nations has made it necessary
to examine and evaluate the New Mexico mine wastes for
their critical mineral and future mining potential. There are
about 15,000 abandoned legacy mine features varying from
shallow prospect pits to deep mine shafts in the 274 mining
districts in New Mexico (NM) (including coal, uranium,
metals, and industrial minerals districts). There is a need
to classify these wastes to understand their composition,
properly estimate the quantity, and evaluate the potential
economic value. Since most of the earlier operations and
exploitation were focused on precious and base metals, it
would be good to now turn our attention to examine these
wastes for potential critical minerals.
It is also necessary to perform paste pH tests and par-
ticle size analyses on samples collected since these factors
can affect weathering and the migration of heavy metals.
Acid rock drainage (ARD) or acid mine drainage (AMD)
is a concern for mine waste management (Karlsson et al.,
2018) and soil pH is an effective indicator for ARD.
The Hillsboro district has had over a century worth of
mining history with no to little reclamation. This, coupled
with Copper Flat’s porphyry copper deposit and carbonate-
hosted Ag-Mn and Pb-Zn deposits makes it an interesting
location for these studies (Munroe, 1999). The Carlisle-
Center mines in the Steeple Rock district, west of Silver
City, is characterized by a low sulfidation volcanic epither-
mal system which contains Au-Ag veins and other deposit
types making it another interesting site for this research
24-042
Geochemistry of Critical Minerals in Mine Wastes at Hillsboro
and Steeple Rock Districts, New Mexico
Abena S. Acheampong-Mensah
New Mexico Institute of Mining and Technology,
Socorro, NM
Virginia T. McLemore
New Mexico Bureau of Geology and Mineral
Resources, Socorro, NM.
ABSTRACT
Critical mineral endowment of mine wastes in two min-
ing districts in New Mexico (Copper Flat at Hillsboro and
Carlisle-Center mines in the Steeple Rock district) will be
characterized and estimated. “Beta-testing” of USGS pro-
cedures was performed. Potential critical minerals at these
deposits include As, Bi, Te, Zn, Co, Ni, Mg, Mn, and fluo-
rite. pH and particle size of samples were analyzed to deter-
mine weathering and migration potential of heavy metals.
Soil pH was also measured to determine the potential for
Acid Rock Drainage. The pH of the waste rock piles ranged
from 3.66 to 5.67 which indicates fine- grained pyrite or
sulfide oxidation. The samples collected from the tailings
however, showed a different range of pH, from 6.30 to 8.62,
probably due to the presence of carbonates. Difference in
particle size fractions and its distribution along the slope are
generally influenced by natural occurrences (e.g., gravity
and pre-mining hydrothermal alteration) and operational
activities such as material piling or dumping. Future work
includes analyses of mineralogy and particle size correla-
tion and estimation of critical mineral endowment of these
mine wastes at New Mexico.
INTRODUCTION
According to the Energy Act of 2020, a critical mineral is
a non-fuel mineral or mineral resource that is crucial to
the U.S.’s economic and national security with a poten-
tial disruption in its supply. Most of our electronic equip-
ment, such as smartphones, laptops, computer chips, wind
turbines, hybrid, and electric cars, etc., depend on these
rare earth elements (REE) and other critical minerals. This
coupled with the anticipated rise in demand for critical
minerals and the potential shortage of production capac-
ity from China and other nations has made it necessary
to examine and evaluate the New Mexico mine wastes for
their critical mineral and future mining potential. There are
about 15,000 abandoned legacy mine features varying from
shallow prospect pits to deep mine shafts in the 274 mining
districts in New Mexico (NM) (including coal, uranium,
metals, and industrial minerals districts). There is a need
to classify these wastes to understand their composition,
properly estimate the quantity, and evaluate the potential
economic value. Since most of the earlier operations and
exploitation were focused on precious and base metals, it
would be good to now turn our attention to examine these
wastes for potential critical minerals.
It is also necessary to perform paste pH tests and par-
ticle size analyses on samples collected since these factors
can affect weathering and the migration of heavy metals.
Acid rock drainage (ARD) or acid mine drainage (AMD)
is a concern for mine waste management (Karlsson et al.,
2018) and soil pH is an effective indicator for ARD.
The Hillsboro district has had over a century worth of
mining history with no to little reclamation. This, coupled
with Copper Flat’s porphyry copper deposit and carbonate-
hosted Ag-Mn and Pb-Zn deposits makes it an interesting
location for these studies (Munroe, 1999). The Carlisle-
Center mines in the Steeple Rock district, west of Silver
City, is characterized by a low sulfidation volcanic epither-
mal system which contains Au-Ag veins and other deposit
types making it another interesting site for this research