3
five-element veins are hydrothermal veins that contain sil-
ver (Ag), cobalt (Co), nickel (Ni), bismuth (Bi), and arsenic
(As) along with other elements like base metals (Pb, Cu,
and Zn), U, Sn, and others. They contain high-grade silver
(1000s g/t Ag), but are low tonnage (1 Mt) and low in
Au and Cu. Ag, Bi, and As are commonly found as native
elements, whereas Co and Ni are found as arsenides and/
or sulfides. This deposit type is complex and these minerals
usually are not found together in the same environment.
There are many subtypes or variations of this deposit type,
since some elements do not occur at all localities.
In 1881, development began in the district with
the discovery of the unusual Ag-Co-Ni deposits at the
Alhambra mine (Gillerman and Whitebread, 1953).
Although production records are lost, it is estimated that
over $1,000,000 was produced from the district from1883
to 1893, when silver prices dropped due to the silver panic
of 1893 (McLemore, 2024). In 1920, pitchblende (urani-
nite) was recognized in mine dumps in the area, and in
1949 the area became of interest as a possible source of U,
Ni, and Co. Types of additional deposits found in the Black
Hawk mining district include: Laramide veins, W placer
deposits, REE-bearing episyenites and pegmatites.
Total metal production from 1883–1960 is esti-
mated at 1,286,000 oz Ag, 3,000 lbs Cu, and 4,000 lbs
Pb (McLemore et al., 1996 McLemore, 2024). The pro-
duction primarily came from narrow carbonate-dominated
veins mined at five occurrences, with the Alhambra and
Black Hawk mines being the most significant. In addition,
10,542 short tons of (2.7–71% WO3) tungsten ore (Richter
and Lawrence, 1983 Dale and McKinney, 1959) and 615
short tons of fluorspar ore have been produced from the
district (Williams, 1966 McAnulty, 1978). Critical min-
erals in Black Hawk district include Co, Ni, As, Cu, Ba,
and Zn, but only copper was produced. Mine dumps were
sampled for this project.
Proterozoic quartz-diorite gneiss and granite are the
predominant rock types in the area, approximately 1.4 bil-
lion years old (Hedlund, 1981), and are intruded by pegma-
tite, diabase, and aplite dikes, as well as the Late Cretaceous
Twin Peaks monzonite porphyry, which is around 75.0–
75.7 million years ago (Amato et al., 2017). The veins in
this region are generally hosted within Proterozoic quartz
diorite gneiss (Figure 4).
Copper Flat Mine, Hillsboro District, Sierra County
The copper Flat mine is a porphyry copper deposit located
in Hillsboro mining district in central Sierra County, 20
miles from Truth or Consequences. The district was dis-
covered in 1877 and produced 1.5 million short tons ore
containing Cu, Au, and Ag in from March to June 1982
(McLemore, 2000, 2017) before production ceased in
1982. The known critical minerals found in the Copper
Flat tailings include Cu, Te, and Zn.
The porphyry copper at the Copper Flat mine has low-
grade copper disseminated and in veinlets among a matrix
consisting of quartz, feldspars, and various copper minerals.
Figure 3. Southwestern New Mexico mining districts
Figure 4. Geologic map of the Black Hawk mining
district, Grant County, New Mexico. From (Gillerman and
Whitebread, 1953)
five-element veins are hydrothermal veins that contain sil-
ver (Ag), cobalt (Co), nickel (Ni), bismuth (Bi), and arsenic
(As) along with other elements like base metals (Pb, Cu,
and Zn), U, Sn, and others. They contain high-grade silver
(1000s g/t Ag), but are low tonnage (1 Mt) and low in
Au and Cu. Ag, Bi, and As are commonly found as native
elements, whereas Co and Ni are found as arsenides and/
or sulfides. This deposit type is complex and these minerals
usually are not found together in the same environment.
There are many subtypes or variations of this deposit type,
since some elements do not occur at all localities.
In 1881, development began in the district with
the discovery of the unusual Ag-Co-Ni deposits at the
Alhambra mine (Gillerman and Whitebread, 1953).
Although production records are lost, it is estimated that
over $1,000,000 was produced from the district from1883
to 1893, when silver prices dropped due to the silver panic
of 1893 (McLemore, 2024). In 1920, pitchblende (urani-
nite) was recognized in mine dumps in the area, and in
1949 the area became of interest as a possible source of U,
Ni, and Co. Types of additional deposits found in the Black
Hawk mining district include: Laramide veins, W placer
deposits, REE-bearing episyenites and pegmatites.
Total metal production from 1883–1960 is esti-
mated at 1,286,000 oz Ag, 3,000 lbs Cu, and 4,000 lbs
Pb (McLemore et al., 1996 McLemore, 2024). The pro-
duction primarily came from narrow carbonate-dominated
veins mined at five occurrences, with the Alhambra and
Black Hawk mines being the most significant. In addition,
10,542 short tons of (2.7–71% WO3) tungsten ore (Richter
and Lawrence, 1983 Dale and McKinney, 1959) and 615
short tons of fluorspar ore have been produced from the
district (Williams, 1966 McAnulty, 1978). Critical min-
erals in Black Hawk district include Co, Ni, As, Cu, Ba,
and Zn, but only copper was produced. Mine dumps were
sampled for this project.
Proterozoic quartz-diorite gneiss and granite are the
predominant rock types in the area, approximately 1.4 bil-
lion years old (Hedlund, 1981), and are intruded by pegma-
tite, diabase, and aplite dikes, as well as the Late Cretaceous
Twin Peaks monzonite porphyry, which is around 75.0–
75.7 million years ago (Amato et al., 2017). The veins in
this region are generally hosted within Proterozoic quartz
diorite gneiss (Figure 4).
Copper Flat Mine, Hillsboro District, Sierra County
The copper Flat mine is a porphyry copper deposit located
in Hillsboro mining district in central Sierra County, 20
miles from Truth or Consequences. The district was dis-
covered in 1877 and produced 1.5 million short tons ore
containing Cu, Au, and Ag in from March to June 1982
(McLemore, 2000, 2017) before production ceased in
1982. The known critical minerals found in the Copper
Flat tailings include Cu, Te, and Zn.
The porphyry copper at the Copper Flat mine has low-
grade copper disseminated and in veinlets among a matrix
consisting of quartz, feldspars, and various copper minerals.
Figure 3. Southwestern New Mexico mining districts
Figure 4. Geologic map of the Black Hawk mining
district, Grant County, New Mexico. From (Gillerman and
Whitebread, 1953)