5
GEOCHEMICAL ANALYSES
Geochemical data are a critical part of evaluation of critical
minerals resources. Geochemical analyses of samples col-
lected for this study were determined by ALS Laboratories
and the USGS laboratory. Samples were submitted to the
laboratory. Duplicate samples and standards were analyzed
and uncertainty of analyses is generally 5%. Chemical
plots were created using ioGAS-64 (ioGAS ™ -REFLEX
(reflexnow.com). Chemical analyses will be released in
future reports.
Particle Size Analyses
As part of characterizing the mine waste, some samples
were sieved into different particle size fractions in order
to compare concentrations of critical minerals in different
size fractions. Two samples from the Black Kawk district
(Alhambra mine wastes) were selected. The test was per-
formed according to ASTM D422-63 standard test method
for particle size analyses of soils using stainless-steel sieves,
specifically No. 4 (4.75mm), No. 14 (1.40mm), No. 40
(0.417mm), No. 60 (0.246mm), No. 80 (0.177mm), and
No 200 (0.074mm).
Paste pH and Fizz Test
When sulfidic minerals (mostly pyrite (FeS2)) are exposed
to air, water, and bacteria, these sulfidic minerals can oxi-
dize and break down to form acid drainage. The acidic
conditions enable various heavy metals within the minerals
to dissolve into the ground and surface water. A sample is
typically considered acid generating if the pH is less than 4
(Borden, 2001). In order to determine the pH of the pore
water produced by the dissolution of secondary mineral
phases on the surfaces of oxidized rock particles, paste tests
are used to assess the geochemical behavior of mine waste
materials subject to weathering in the field (Figure 7A).
Also, fizz test was performed to determine how much
hydrochloric acid (HCl) needs to be added to a 2 g sample
in order to digest carbonate (and other neutralizing miner-
als) and then determine the amount of NP (Figure 7B).
RESULTS AND DISCUSSION
Petrography and Mineralogy
The petrographic analyses of mine wastes samples showed
that predominant minerals are quartz, potassium feldspar
and clay. Overall, 33 samples from Black Hawk district
mine waste rock piles and 36 samples form Copper Flat
mine tailings were analyzed using XRD analyses to better
understand the mineralogy.
Based on Black Hawk district mine wastes XRD results:
• Quartz (SiO2) is the most predominant mineral.
• Samples contain clay minerals such as illite
(K0.65Al2[Al0.65Si3.35O10](OH)2) and kaolinite
(Al2Si2O5(OH)4).
• Also, a few samples contain sphalerite (ZnS) and
dolomite (CaMg(CO3)2), albite (NaAlSi3O8).
Figure 6. Copper Flat mine tailing profile
sampling
Figure 7. A) Paste pH test on sieved samples, B) Fizz test on
mine waste sample
GEOCHEMICAL ANALYSES
Geochemical data are a critical part of evaluation of critical
minerals resources. Geochemical analyses of samples col-
lected for this study were determined by ALS Laboratories
and the USGS laboratory. Samples were submitted to the
laboratory. Duplicate samples and standards were analyzed
and uncertainty of analyses is generally 5%. Chemical
plots were created using ioGAS-64 (ioGAS ™ -REFLEX
(reflexnow.com). Chemical analyses will be released in
future reports.
Particle Size Analyses
As part of characterizing the mine waste, some samples
were sieved into different particle size fractions in order
to compare concentrations of critical minerals in different
size fractions. Two samples from the Black Kawk district
(Alhambra mine wastes) were selected. The test was per-
formed according to ASTM D422-63 standard test method
for particle size analyses of soils using stainless-steel sieves,
specifically No. 4 (4.75mm), No. 14 (1.40mm), No. 40
(0.417mm), No. 60 (0.246mm), No. 80 (0.177mm), and
No 200 (0.074mm).
Paste pH and Fizz Test
When sulfidic minerals (mostly pyrite (FeS2)) are exposed
to air, water, and bacteria, these sulfidic minerals can oxi-
dize and break down to form acid drainage. The acidic
conditions enable various heavy metals within the minerals
to dissolve into the ground and surface water. A sample is
typically considered acid generating if the pH is less than 4
(Borden, 2001). In order to determine the pH of the pore
water produced by the dissolution of secondary mineral
phases on the surfaces of oxidized rock particles, paste tests
are used to assess the geochemical behavior of mine waste
materials subject to weathering in the field (Figure 7A).
Also, fizz test was performed to determine how much
hydrochloric acid (HCl) needs to be added to a 2 g sample
in order to digest carbonate (and other neutralizing miner-
als) and then determine the amount of NP (Figure 7B).
RESULTS AND DISCUSSION
Petrography and Mineralogy
The petrographic analyses of mine wastes samples showed
that predominant minerals are quartz, potassium feldspar
and clay. Overall, 33 samples from Black Hawk district
mine waste rock piles and 36 samples form Copper Flat
mine tailings were analyzed using XRD analyses to better
understand the mineralogy.
Based on Black Hawk district mine wastes XRD results:
• Quartz (SiO2) is the most predominant mineral.
• Samples contain clay minerals such as illite
(K0.65Al2[Al0.65Si3.35O10](OH)2) and kaolinite
(Al2Si2O5(OH)4).
• Also, a few samples contain sphalerite (ZnS) and
dolomite (CaMg(CO3)2), albite (NaAlSi3O8).
Figure 6. Copper Flat mine tailing profile
sampling
Figure 7. A) Paste pH test on sieved samples, B) Fizz test on
mine waste sample