2
quantify the distribution of rare earth elements (REE) and
critical minerals in coal beds and related stratigraphic units
in coal basins throughout the U.S.
Coal deposits from throughout the world are known to
contain high concentrations of critical minerals and REE
(Dai and Finkelman, 2018), but a basin-wide geochemical
and mineralogical characterization study of New Mexico
coals is needed to determine the potential for critical min-
erals and REE. The purposes of the CORE-CM project are
to 1) identify, quantify, and characterize the distribution of
critical minerals, including REE, in coal beds and related
stratigraphic units in the San Juan and Raton basins in New
Mexico, 2) identify possible sources of critical minerals and
REE in the basins, 3) identify the coal mine and nonfuel
carbon-based waste products that could contain critical
minerals and REE, and 4) test and develop new technolo-
gies in identifying and quantifying critical minerals and
REE in high-fidelity geologic models. In this paper we are
presenting data on three types of deposits in the San Juan
Basin. Future reports will discuss the potential for REE
and critical minerals in adjacent strata in the San Juan and
Raton basins.
GEOLOGY
The San Juan Basin is a predominant Laramide (Upper
Cretaceous–Early Tertiary age structural basin in north-
ern New Mexico and southern Colorado that host and
produced important energy and mineral resources, includ-
ing coal, uranium, petroleum, and gas (Figure 1, 2).
Stratigraphic units in the San Juan Basin dips inward from
the highlands towards the center of the basin, creating a
trough-like feature. San Juan Basin has three major coal-
bearing units: Crevasse Canyon, Menefee, and Fruitland
formations in 26 coal fields.
Coal is mined in New Mexico and fuels electrical gen-
erating plants in New Mexico and Arizona. Coal mining
on a significant scale began in New Mexico in 1862, when
U.S. Army troops from Fort Craig opened the Government
mine in the Carthage field (Socorro County) to supply
coal for smithing at Forts Seldon, Bayard, and Stanton.
Coal mining continued to expand in the 1880s through-
out New Mexico supplying the railroads with fuel. Three
surface mines remain in operation today El Segundo, Lee
Ranch and Navajo. New Mexico is 12th in coal produc-
tion in U.S. in 2020, with production at approximately
10,249,000 short tons. However, production is decreasing
because of mine closures. New Mexico is 15th in estimated
recoverable coal reserves in U.S. (65 million short tons of
recoverable reserves at mines and 6,719 million short tons
estimated recoverable reserves in the basin).
Coal is a sedimentary rock that is composed of more
than 50% by weight of organic material and is formed by
the compaction of decaying plant material deposited in
ancient peat swamps or mires. Coal is readily combustible
and is burned for fuel. Several factors beside the thickness
and quality of the coal determine whether a coal deposit is
economic: 1) the technology available for extraction, 2) dis-
tance to a market, and 3) available transportation network.
Throughout the history of mining coal in New Mexico,
these factors have changed. Coal also contains minerals
that are noncombustible and do not burn. These minerals
could contain REE and other critical minerals that could be
recovered from coal mining or from the coal ash remaining
after the coal is burned. In the future, the concentration of
critical minerals, including REE could be a factor in pro-
ducing coal deposits.
Humates are weathered coal or highly organic mudstone
that are found in the coal-bearing sequences (Newcomer et
al., 2021). They can transition to coal at depth (Figure 3).
They are locally also termed leonardite or weathered lignite
other terms are explained in Newcomer et al. (2021). The
difference between coal and humate is brownish color and
more humic acid content in humates and black coal burns,
whereas high quality humate dissolves in water.
New Mexico has significant deposits of humates, pre-
dominantly in the Fruitland and Menefee formations in
the eastern San Juan Basin. Humate is produced from ~10
mines and mills in New Mexico. The Horizon Ag Products
mine and mill are south of Cuba. Menefee Mining operates
Figure 1. Location map of coal fields in the San Juan basin,
New Mexico (modified from Hoffman, 2017). Active coal
mines are surface operations. Lee Ranch mine suspended
operations in 2016, but plans to reopen. Coal fields are
summarized in Table 1 (end of report). Only the Four
Corners power plant remains open
quantify the distribution of rare earth elements (REE) and
critical minerals in coal beds and related stratigraphic units
in coal basins throughout the U.S.
Coal deposits from throughout the world are known to
contain high concentrations of critical minerals and REE
(Dai and Finkelman, 2018), but a basin-wide geochemical
and mineralogical characterization study of New Mexico
coals is needed to determine the potential for critical min-
erals and REE. The purposes of the CORE-CM project are
to 1) identify, quantify, and characterize the distribution of
critical minerals, including REE, in coal beds and related
stratigraphic units in the San Juan and Raton basins in New
Mexico, 2) identify possible sources of critical minerals and
REE in the basins, 3) identify the coal mine and nonfuel
carbon-based waste products that could contain critical
minerals and REE, and 4) test and develop new technolo-
gies in identifying and quantifying critical minerals and
REE in high-fidelity geologic models. In this paper we are
presenting data on three types of deposits in the San Juan
Basin. Future reports will discuss the potential for REE
and critical minerals in adjacent strata in the San Juan and
Raton basins.
GEOLOGY
The San Juan Basin is a predominant Laramide (Upper
Cretaceous–Early Tertiary age structural basin in north-
ern New Mexico and southern Colorado that host and
produced important energy and mineral resources, includ-
ing coal, uranium, petroleum, and gas (Figure 1, 2).
Stratigraphic units in the San Juan Basin dips inward from
the highlands towards the center of the basin, creating a
trough-like feature. San Juan Basin has three major coal-
bearing units: Crevasse Canyon, Menefee, and Fruitland
formations in 26 coal fields.
Coal is mined in New Mexico and fuels electrical gen-
erating plants in New Mexico and Arizona. Coal mining
on a significant scale began in New Mexico in 1862, when
U.S. Army troops from Fort Craig opened the Government
mine in the Carthage field (Socorro County) to supply
coal for smithing at Forts Seldon, Bayard, and Stanton.
Coal mining continued to expand in the 1880s through-
out New Mexico supplying the railroads with fuel. Three
surface mines remain in operation today El Segundo, Lee
Ranch and Navajo. New Mexico is 12th in coal produc-
tion in U.S. in 2020, with production at approximately
10,249,000 short tons. However, production is decreasing
because of mine closures. New Mexico is 15th in estimated
recoverable coal reserves in U.S. (65 million short tons of
recoverable reserves at mines and 6,719 million short tons
estimated recoverable reserves in the basin).
Coal is a sedimentary rock that is composed of more
than 50% by weight of organic material and is formed by
the compaction of decaying plant material deposited in
ancient peat swamps or mires. Coal is readily combustible
and is burned for fuel. Several factors beside the thickness
and quality of the coal determine whether a coal deposit is
economic: 1) the technology available for extraction, 2) dis-
tance to a market, and 3) available transportation network.
Throughout the history of mining coal in New Mexico,
these factors have changed. Coal also contains minerals
that are noncombustible and do not burn. These minerals
could contain REE and other critical minerals that could be
recovered from coal mining or from the coal ash remaining
after the coal is burned. In the future, the concentration of
critical minerals, including REE could be a factor in pro-
ducing coal deposits.
Humates are weathered coal or highly organic mudstone
that are found in the coal-bearing sequences (Newcomer et
al., 2021). They can transition to coal at depth (Figure 3).
They are locally also termed leonardite or weathered lignite
other terms are explained in Newcomer et al. (2021). The
difference between coal and humate is brownish color and
more humic acid content in humates and black coal burns,
whereas high quality humate dissolves in water.
New Mexico has significant deposits of humates, pre-
dominantly in the Fruitland and Menefee formations in
the eastern San Juan Basin. Humate is produced from ~10
mines and mills in New Mexico. The Horizon Ag Products
mine and mill are south of Cuba. Menefee Mining operates
Figure 1. Location map of coal fields in the San Juan basin,
New Mexico (modified from Hoffman, 2017). Active coal
mines are surface operations. Lee Ranch mine suspended
operations in 2016, but plans to reopen. Coal fields are
summarized in Table 1 (end of report). Only the Four
Corners power plant remains open