2
worldwide deposits, the study describes features typical
of the deposit type. These deposits typically have a gen-
eral paragenesis of low grade, ordinary sulfides, followed
by native metal and arsenides/antimonides, then by arse-
nides/antimonides alone, then sulfosalts and sulfides, and
lastly by carbonate gangue minerals. The native metals,
and sometimes the arsenides, typically form large dendritic
or skeletal aggregates. The succession of arsenides shows
mono-arsenides forming first, with nickel following native
silver, and cobalt following native bismuth. These are suc-
ceeded by di- and tri-arsenides, often grading from nickel to
cobalt to iron away from native silver aggregates. The native
phases show re-absorption textures after arsenide precipita-
tion, leaving hollow crusts of arsenides that are later filled
by carbonate gangue. They describe the importance of the
redox state of the system, as sulfides are present before and
after the native metal and arsenide precipitation, and the
unusual textures indicate rapid precipitation far from equi-
librium. Their model to adequately describe their observa-
tions involves a rapid influx of methane or other sulfur poor
hydrocarbons released by “natural fracking” and fracturing
of the host rock to release these highly reducing compounds
into a highly saline metal rich fluid. This leads to precipita-
tion of observed native metal aggregates in zones where the
oxidized ore fluid contacts the reduced organic rich fluid.
Crystallization is kinetically limited to seed crystals, lead-
ing to monomineralic clumps of large skeletal and dendritic
crystal aggregates.
Gillerman and Whitebread (1953) investigated the
Black Hawk district as part of a study on the geology of ura-
nium. They reported small quantities of pitchblende from
the Black Hawk and Alhambra mines of the district, and
the study generated detailed surface maps of both mines, as
well as an overview of the general geology and mineralogy
of the deposit. Minerals were collected from the dumps,
as the mines were inaccessible, and were analyzed using
powder X-ray diffraction and reflected light microscopy.
They identified many ore and gangue minerals, including
pitchblende, native silver, niccolite (nickeline), pyrite, and
carbonates, as well as tentatively identified arsenides like
skutterudite, nickelskutterudite, smaltite, chloanthite, and
rammelsbergite. Previous studies also reported argentite,
cerargyrite (chlorargyrite), ruby silvers (proustite, pyrargy-
rite), millerite, sphalerite, galena, stannite, and bismuthi-
nite, among others.
Figure 1. Districts of southwestern New Mexico with
Laramide porphyry copper deposits, polymetallic veins,
skarns, and plutons. (Gillerman &Whitebread, 1953)
Figure 2. Location map of five-element style and similar
deposits worldwide. (Kissin, 1992)
worldwide deposits, the study describes features typical
of the deposit type. These deposits typically have a gen-
eral paragenesis of low grade, ordinary sulfides, followed
by native metal and arsenides/antimonides, then by arse-
nides/antimonides alone, then sulfosalts and sulfides, and
lastly by carbonate gangue minerals. The native metals,
and sometimes the arsenides, typically form large dendritic
or skeletal aggregates. The succession of arsenides shows
mono-arsenides forming first, with nickel following native
silver, and cobalt following native bismuth. These are suc-
ceeded by di- and tri-arsenides, often grading from nickel to
cobalt to iron away from native silver aggregates. The native
phases show re-absorption textures after arsenide precipita-
tion, leaving hollow crusts of arsenides that are later filled
by carbonate gangue. They describe the importance of the
redox state of the system, as sulfides are present before and
after the native metal and arsenide precipitation, and the
unusual textures indicate rapid precipitation far from equi-
librium. Their model to adequately describe their observa-
tions involves a rapid influx of methane or other sulfur poor
hydrocarbons released by “natural fracking” and fracturing
of the host rock to release these highly reducing compounds
into a highly saline metal rich fluid. This leads to precipita-
tion of observed native metal aggregates in zones where the
oxidized ore fluid contacts the reduced organic rich fluid.
Crystallization is kinetically limited to seed crystals, lead-
ing to monomineralic clumps of large skeletal and dendritic
crystal aggregates.
Gillerman and Whitebread (1953) investigated the
Black Hawk district as part of a study on the geology of ura-
nium. They reported small quantities of pitchblende from
the Black Hawk and Alhambra mines of the district, and
the study generated detailed surface maps of both mines, as
well as an overview of the general geology and mineralogy
of the deposit. Minerals were collected from the dumps,
as the mines were inaccessible, and were analyzed using
powder X-ray diffraction and reflected light microscopy.
They identified many ore and gangue minerals, including
pitchblende, native silver, niccolite (nickeline), pyrite, and
carbonates, as well as tentatively identified arsenides like
skutterudite, nickelskutterudite, smaltite, chloanthite, and
rammelsbergite. Previous studies also reported argentite,
cerargyrite (chlorargyrite), ruby silvers (proustite, pyrargy-
rite), millerite, sphalerite, galena, stannite, and bismuthi-
nite, among others.
Figure 1. Districts of southwestern New Mexico with
Laramide porphyry copper deposits, polymetallic veins,
skarns, and plutons. (Gillerman &Whitebread, 1953)
Figure 2. Location map of five-element style and similar
deposits worldwide. (Kissin, 1992)