3
skutterudite, 3) chalcopyrite-tennantite-galenasphalerite,
and 4) acanthite-jalpaite-pearceite-covellite (Von Bargen,
1979, 1993). Pitchblende is found with minor pyrite, chal-
copyrite, galena, manganocalcite, and various nickel and
cobalt sulfarsenides and arsenides (Gillerman, 1964 Von
Bargen, 1979, 1993).
Precambrian quartz diorite gneiss, which intrudes
quartzite, schist, monzonite, and quartz monzonite, is the
most widespread rock in the district (Figure 3). The mineral
deposits contain silver, nickel, cobalt, and uranium min-
erals. The minerals, which include native silver, argentite,
niccolite, millerite, skutterudite, nickel skutterudite, pitch-
blende, and sphalerite, are in a carbonate gangue. These
rocks are cut by many igneous rocks of pre-Cambrian and
younger age, the most common of which is monzonite
porphyry of probable Late Cretaceous or early Tertiary age
(Gillerman &Whitebread, 1953).
This district contains Ni, Co, Bi, As, and Ag along with
some local elements such as U, Zn, Cu, and Pb. Many of
these elements are critical minerals. Hillebrand (1889) pre-
sented a chemical study of a combination of nickelskut-
terudite and silver. According to von Bargen (1993), the ore
solutions are higher in sulfur and uranium, much lower in
bismuth and antimony content, and had a relatively high
nickel-to-cobalt ratio in Black Hawk district. In this area,
gersdorffite (NiAsS) is frequently found as a thin layer. The
earliest nickel arsenide to form is nickeline (NiAs), which
is frequently covered with gersdorffite or rammelsbergite.
Under polarized light, nickeline is highly anisotropic min-
eral exhibits a color shift from light pink to darker. NiAsx-3,
or nickel-skutterudite, is one of the main deposits of nickel
arsenide. Early mineralogists found it very challenging to
analyze this material chemically due to the combinations
of replacement minerals, gangue, and silver. Of all the arse-
nides, it contains the most cobalt, iron, and sulfur. It also
crystallizes into dodecahedral crystals up to 2 cm in size.
MATERIALS AND METHODS
Sampling and Sample Preparation
See McLemore and Owen (2024) for sampling procedures.
Figure 4 is shows the Black Hawk mine waste sampling
locations (Fig. 4). Some general precautions in sampling
include the following. All equipment has been cleaned to
prevent cross-contamination of the sample. Sampling tools
(buckets, sampling bags, shovels, trowels, and sieves) con-
structed of materials suitable for environmental sampling
(typically stainless steel, plastic, or aluminum). Devices
plated with chrome or other materials are not useful as they
can introduce contaminants to the samples. All equipment
used for sampling had been rinsed with deionized water
and air-dried prior to use. Sample collector wore disposable
gloves while sieving to avoid contamination.
Geochemical Analyses
Geochemical data are a critical part of geologic mapping
and for evaluation for critical mineral resources central
to the mission of Earth MRI. Geochemical analyses of
Figure 2. Southwestern New Mexico districts with
Laramide mineral deposits, polymetallic veins, and plutons
(McLemore, 2008)
Figure 3. Geologic map of the Black Hawk mining
district, Grant County, New Mexico. From (Gillerman &
Whitebread, 1953)
skutterudite, 3) chalcopyrite-tennantite-galenasphalerite,
and 4) acanthite-jalpaite-pearceite-covellite (Von Bargen,
1979, 1993). Pitchblende is found with minor pyrite, chal-
copyrite, galena, manganocalcite, and various nickel and
cobalt sulfarsenides and arsenides (Gillerman, 1964 Von
Bargen, 1979, 1993).
Precambrian quartz diorite gneiss, which intrudes
quartzite, schist, monzonite, and quartz monzonite, is the
most widespread rock in the district (Figure 3). The mineral
deposits contain silver, nickel, cobalt, and uranium min-
erals. The minerals, which include native silver, argentite,
niccolite, millerite, skutterudite, nickel skutterudite, pitch-
blende, and sphalerite, are in a carbonate gangue. These
rocks are cut by many igneous rocks of pre-Cambrian and
younger age, the most common of which is monzonite
porphyry of probable Late Cretaceous or early Tertiary age
(Gillerman &Whitebread, 1953).
This district contains Ni, Co, Bi, As, and Ag along with
some local elements such as U, Zn, Cu, and Pb. Many of
these elements are critical minerals. Hillebrand (1889) pre-
sented a chemical study of a combination of nickelskut-
terudite and silver. According to von Bargen (1993), the ore
solutions are higher in sulfur and uranium, much lower in
bismuth and antimony content, and had a relatively high
nickel-to-cobalt ratio in Black Hawk district. In this area,
gersdorffite (NiAsS) is frequently found as a thin layer. The
earliest nickel arsenide to form is nickeline (NiAs), which
is frequently covered with gersdorffite or rammelsbergite.
Under polarized light, nickeline is highly anisotropic min-
eral exhibits a color shift from light pink to darker. NiAsx-3,
or nickel-skutterudite, is one of the main deposits of nickel
arsenide. Early mineralogists found it very challenging to
analyze this material chemically due to the combinations
of replacement minerals, gangue, and silver. Of all the arse-
nides, it contains the most cobalt, iron, and sulfur. It also
crystallizes into dodecahedral crystals up to 2 cm in size.
MATERIALS AND METHODS
Sampling and Sample Preparation
See McLemore and Owen (2024) for sampling procedures.
Figure 4 is shows the Black Hawk mine waste sampling
locations (Fig. 4). Some general precautions in sampling
include the following. All equipment has been cleaned to
prevent cross-contamination of the sample. Sampling tools
(buckets, sampling bags, shovels, trowels, and sieves) con-
structed of materials suitable for environmental sampling
(typically stainless steel, plastic, or aluminum). Devices
plated with chrome or other materials are not useful as they
can introduce contaminants to the samples. All equipment
used for sampling had been rinsed with deionized water
and air-dried prior to use. Sample collector wore disposable
gloves while sieving to avoid contamination.
Geochemical Analyses
Geochemical data are a critical part of geologic mapping
and for evaluation for critical mineral resources central
to the mission of Earth MRI. Geochemical analyses of
Figure 2. Southwestern New Mexico districts with
Laramide mineral deposits, polymetallic veins, and plutons
(McLemore, 2008)
Figure 3. Geologic map of the Black Hawk mining
district, Grant County, New Mexico. From (Gillerman &
Whitebread, 1953)