XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 815
It requires small-scale miners to follow responsible mining
practices and adhere to government regulations. In 2023,
there were only 57 declared Minahang Bayan sites in the
country. (MGB, 2023).
Small-scale mining operators are mostly known to
mine and process gold. They utilize underground mining
through narrow tunnels (as shown in Figure 1), with some
abandoned tunnels of large mining operations, and manual
hauling of ores. On the surface, the large pieces of rocks
are crushed by hand until the size is sufficient to be fed
into a rod mill for grinding (Figure 1). The ground ore is
transferred to a tank to extract the gold. Some operators
use cyanide (cyanidation) while others use mercury (amal-
gamation) in gold extraction which takes days to weeks.
After cyanidation or amalgamation, the gold is washed and
undergoes purification by blowtorch.
NON-CYANIDE, NON-MERCURY GOLD
EXTRACTION FOR SMALL-SCALE
MINERS
Cyanidation is still the widespread method for gold extrac-
tion because it is cheap and easy to use. However, the
environmental impacts of cyanide are also well-known
(ATSDR, 2006 Gonzalez-Valoys et al., 2022 Jaszczak et
al., 2017). Cyanide is a toxic substance that can damage to
the environment and is a risk to public health if released to
the environment.
To promote responsible mining practices, the gov-
ernment is exploring ways to reduce the use of the highly
toxic cyanide and mercury. The government, through the
Department of Science and Technology (DOST), funded a
research project that would 1) establish a processing plant
for small-scale miners utilizing clean and sustainable pro-
cess for gold extraction, and 2) develop a capacity building
program for small-scale mining communities. The research
lasted for ten (10) years from 2009 to 2019which included
development of a non-cyanide, non-mercury gold extrac-
tion method applicable to small-scale mining operation,
construction of processing plants, conducting interviews
and focused group discussions with small-scale min-
ing communities, training, lectures and workshops with
operators, and hands-on demonstration of equipment.
The small-scale mining operators were also involved in the
commissioning of the processing plants. A total of four (4)
processing plants were constructed in 4 major small-scale
mining areas in the Philippines. The processing plants are
now being managed by the Local Government Unit or the
DOST Regional Office and operated by small-scale mining
associations in the area.
The non-cyanide, non-mercury gold extraction method
developed for small-scale mining operation is shown in
Figure 2. It is composed of jaw crusher as the primary
crushing, vibrating screen and roll crusher as secondary
crushing. The crushed ore is fed to a ball mill-hydrocyclone
circuit. The hydrocyclone overflow enters the falcon gravity
concentrator to recover the native gold. The tailings flow
to a thickener where the clarified water is re-used in the
process. On the other hand, the concentrate is treated by
a shaking table as the cleaning stage. The table concentrate
is taken as a final product. The middlings and the tailings
are combined and treated via flotation to recover the gold
associated with sulfides. The flotation tailings also flow to
a thickener where the clarified water is re-used. The con-
centrate is then treated by chlorination to extract the gold.
After leaching, the leachate undergoes filtration to separate
the pregnant solution from the residue. The pregnant solu-
tion goes to a precipitation tank to precipitate the gold.
The barren solution is first neutralized prior to disposal in
a treatment pond.
The method was deployed in the processing plants.
The involvement of small-scale miners during the com-
missioning was beneficial for both the researchers and the
miners. For the miners, their involvement allowed them to
gain more experience, hence more confidence, in operat-
ing all the equipment in the plant. It was an opportunity
for the researchers to explain and show the method so that
the small-scale miners could understand the method better.
The miners also suggested some practical adjustments in
Figure 1. A tunnel (left), rod mill grinding (middle) and cyanidation tanks (right) of a small-scale mining operation
It requires small-scale miners to follow responsible mining
practices and adhere to government regulations. In 2023,
there were only 57 declared Minahang Bayan sites in the
country. (MGB, 2023).
Small-scale mining operators are mostly known to
mine and process gold. They utilize underground mining
through narrow tunnels (as shown in Figure 1), with some
abandoned tunnels of large mining operations, and manual
hauling of ores. On the surface, the large pieces of rocks
are crushed by hand until the size is sufficient to be fed
into a rod mill for grinding (Figure 1). The ground ore is
transferred to a tank to extract the gold. Some operators
use cyanide (cyanidation) while others use mercury (amal-
gamation) in gold extraction which takes days to weeks.
After cyanidation or amalgamation, the gold is washed and
undergoes purification by blowtorch.
NON-CYANIDE, NON-MERCURY GOLD
EXTRACTION FOR SMALL-SCALE
MINERS
Cyanidation is still the widespread method for gold extrac-
tion because it is cheap and easy to use. However, the
environmental impacts of cyanide are also well-known
(ATSDR, 2006 Gonzalez-Valoys et al., 2022 Jaszczak et
al., 2017). Cyanide is a toxic substance that can damage to
the environment and is a risk to public health if released to
the environment.
To promote responsible mining practices, the gov-
ernment is exploring ways to reduce the use of the highly
toxic cyanide and mercury. The government, through the
Department of Science and Technology (DOST), funded a
research project that would 1) establish a processing plant
for small-scale miners utilizing clean and sustainable pro-
cess for gold extraction, and 2) develop a capacity building
program for small-scale mining communities. The research
lasted for ten (10) years from 2009 to 2019which included
development of a non-cyanide, non-mercury gold extrac-
tion method applicable to small-scale mining operation,
construction of processing plants, conducting interviews
and focused group discussions with small-scale min-
ing communities, training, lectures and workshops with
operators, and hands-on demonstration of equipment.
The small-scale mining operators were also involved in the
commissioning of the processing plants. A total of four (4)
processing plants were constructed in 4 major small-scale
mining areas in the Philippines. The processing plants are
now being managed by the Local Government Unit or the
DOST Regional Office and operated by small-scale mining
associations in the area.
The non-cyanide, non-mercury gold extraction method
developed for small-scale mining operation is shown in
Figure 2. It is composed of jaw crusher as the primary
crushing, vibrating screen and roll crusher as secondary
crushing. The crushed ore is fed to a ball mill-hydrocyclone
circuit. The hydrocyclone overflow enters the falcon gravity
concentrator to recover the native gold. The tailings flow
to a thickener where the clarified water is re-used in the
process. On the other hand, the concentrate is treated by
a shaking table as the cleaning stage. The table concentrate
is taken as a final product. The middlings and the tailings
are combined and treated via flotation to recover the gold
associated with sulfides. The flotation tailings also flow to
a thickener where the clarified water is re-used. The con-
centrate is then treated by chlorination to extract the gold.
After leaching, the leachate undergoes filtration to separate
the pregnant solution from the residue. The pregnant solu-
tion goes to a precipitation tank to precipitate the gold.
The barren solution is first neutralized prior to disposal in
a treatment pond.
The method was deployed in the processing plants.
The involvement of small-scale miners during the com-
missioning was beneficial for both the researchers and the
miners. For the miners, their involvement allowed them to
gain more experience, hence more confidence, in operat-
ing all the equipment in the plant. It was an opportunity
for the researchers to explain and show the method so that
the small-scale miners could understand the method better.
The miners also suggested some practical adjustments in
Figure 1. A tunnel (left), rod mill grinding (middle) and cyanidation tanks (right) of a small-scale mining operation