6
Paste pH Tests and Net Acid Generation Graph
The Black Hawk mine waste samples exhibit consistent
geochemical behavior. The paste pH test showed that paste
samples have pH ranges between 5.23 to 8.47 (Table 1).
Static tests are geochemical analyses to predict the
potential of a waste sample to produce acid. The generation
of acid in sulfidic wastes can be determined by Acid Base
Accounting (ABA) and Net Acid Generation (NAG) tests.
To enable waste sorting, the NAGpH value is typically plot-
ted against the Neutralization Potential Ratio (NPR) value.
Acid Base Accounting refers to the numerical data
used to predict acid generation. The three components of
the ABA are: (1) determination of acid production (2)
determination of acid consumption and (3) calculation of
net acid production or consumption using the data from
(1) and (2). The Acid Potential (AP) is measured by analyz-
ing the sample for its sulfur content. The Neutralization
Potential (NP) is determined by analyzing the acidity
consumption of a sample in acid (HCl or H2SO4). Net
Neutralization Potential (NNP) gives the waste’s capacity to
neutralize any acid generated and is the difference between
the Acid Potential and the Neutralization Potential. The
ratio NP/AP, known as the Neutralization Potential Ratio
(NPR) (Lottermoser, 2010).
AP (kg CaCO3/tonnes) =wt.% S × 31.25
NP (total C) =wt.% C × 83.3 x C
NNP =NP – AP, NPR =NP/AP
Figure 10 shows is combined ARD classification plot and is
illustrating that the Black Hawk mine wastes samples fall in
the non-acid forming quadrants (Fig. 10).
PRELIMINARY CONCLUSION
The main objective of this study was to evaluate the critical
minerals in Black Hawk mine wastes. The presence of these
critical minerals in the waste material could be of economic
interest. The recognition of critical minerals is seen as cru-
cial for enhancing the overall economic wellbeing of the
United States. Determination of acid generating potential
in the area suggests that Black Hawk mine wastes are in
non-acid forming quarter.
ACKNOWLEDGMENT
This work is part of ongoing research of the economic geol-
ogy of mineral resources in New Mexico at NMBGMR,
Table 1. Black Hawk mine wastes paste pH recorded and fizz
test results.
Sample ID
Wt. of
Sample (g)
Fizz
Test
(Y/N) pH Ave. pH
BLHK501 25.011 No 5.76 5.78
25.007 5.80
BLHK503 25.011 No 5.23 5.235
25.004 5.24
BLHK507 25.012 Yes 7.56 7.85
25.016 8.14
BLHK508 25.010 Yes 7.71 7.635
25.015 7.56
BLHK510 25.018 No 8.12 8.195
25.006 8.27
BLHK512 25.001 No 6.93 6.955
25.010 6.98
BLHK517 25.002 No 6.82 6.91
25.014 7.00
BLHK542 25.060 Yes 8.27 8.37
25.070 8.47
BLHK549 25.040 No 7.21 7.355
25.020 7.50
Figure 10. Acid Rock Dranaige (ARD) graph of Black Hawk
mine waste samples
Paste pH Tests and Net Acid Generation Graph
The Black Hawk mine waste samples exhibit consistent
geochemical behavior. The paste pH test showed that paste
samples have pH ranges between 5.23 to 8.47 (Table 1).
Static tests are geochemical analyses to predict the
potential of a waste sample to produce acid. The generation
of acid in sulfidic wastes can be determined by Acid Base
Accounting (ABA) and Net Acid Generation (NAG) tests.
To enable waste sorting, the NAGpH value is typically plot-
ted against the Neutralization Potential Ratio (NPR) value.
Acid Base Accounting refers to the numerical data
used to predict acid generation. The three components of
the ABA are: (1) determination of acid production (2)
determination of acid consumption and (3) calculation of
net acid production or consumption using the data from
(1) and (2). The Acid Potential (AP) is measured by analyz-
ing the sample for its sulfur content. The Neutralization
Potential (NP) is determined by analyzing the acidity
consumption of a sample in acid (HCl or H2SO4). Net
Neutralization Potential (NNP) gives the waste’s capacity to
neutralize any acid generated and is the difference between
the Acid Potential and the Neutralization Potential. The
ratio NP/AP, known as the Neutralization Potential Ratio
(NPR) (Lottermoser, 2010).
AP (kg CaCO3/tonnes) =wt.% S × 31.25
NP (total C) =wt.% C × 83.3 x C
NNP =NP – AP, NPR =NP/AP
Figure 10 shows is combined ARD classification plot and is
illustrating that the Black Hawk mine wastes samples fall in
the non-acid forming quadrants (Fig. 10).
PRELIMINARY CONCLUSION
The main objective of this study was to evaluate the critical
minerals in Black Hawk mine wastes. The presence of these
critical minerals in the waste material could be of economic
interest. The recognition of critical minerals is seen as cru-
cial for enhancing the overall economic wellbeing of the
United States. Determination of acid generating potential
in the area suggests that Black Hawk mine wastes are in
non-acid forming quarter.
ACKNOWLEDGMENT
This work is part of ongoing research of the economic geol-
ogy of mineral resources in New Mexico at NMBGMR,
Table 1. Black Hawk mine wastes paste pH recorded and fizz
test results.
Sample ID
Wt. of
Sample (g)
Fizz
Test
(Y/N) pH Ave. pH
BLHK501 25.011 No 5.76 5.78
25.007 5.80
BLHK503 25.011 No 5.23 5.235
25.004 5.24
BLHK507 25.012 Yes 7.56 7.85
25.016 8.14
BLHK508 25.010 Yes 7.71 7.635
25.015 7.56
BLHK510 25.018 No 8.12 8.195
25.006 8.27
BLHK512 25.001 No 6.93 6.955
25.010 6.98
BLHK517 25.002 No 6.82 6.91
25.014 7.00
BLHK542 25.060 Yes 8.27 8.37
25.070 8.47
BLHK549 25.040 No 7.21 7.355
25.020 7.50
Figure 10. Acid Rock Dranaige (ARD) graph of Black Hawk
mine waste samples