3064 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
while B and C are used for ore processing. The B and C
lines consist of primary AG mill and secondary pebble
mill. Grinding circuit includes screens, from which coarse
material is sent to the primary mill while fines are sent to
a hydrocyclone battery. A part of screens underflow passes
through a gravimetric Knelson separator. Underflow from
cyclones is sent to the pebble mill via a flash flotation cell,
while fines are sent to flotation.
The B and C flotation lines consist of three circuits:
Cu/Pb-flotation, Cu/Pb-separation, and Zn-flotation. The
Kankberg Au-tellurium ore is typically processed on the C
line utilizing the Cu/Pb-flotation circuit, consisting of five
rougher flotation cells and four scavenger cells, followed
by four cleaner cells. Collectors PAX (74% potassium iso-
pentyl xanthate, 17% potassium methyl-butyl xanthate)
and Hostaflot 7869 (30–50% dithiophosphate, 25–30%
thiocarbamate) are used, with Dowfroth 250 (glycol) as the
frother. Sodium bisulfite is added for pH control and to
benefit Au-minerals flotation. Flotation tails are directed
to the CIL plant, while the Au-Te-concentrate undergoes
batch cyanide leaching at 65 °C. Figure 1 provides a top
view of the Boliden Concentrator, illustrating the three dis-
tinct circuit lines.
Geology
The Åkulla Kankberg ore is mined from the Åkulla Au-Te
mineralisation, a mineralogically distinct and newly recog-
nized ore deposit style in the Skellefteå District (Nordfeldt
et al. 2019). The mineralisation is characterized by the
abundance of topaz-quartz alteration, occurrence of anda-
lusite, white mica, Au-Te enrichments, and a paucity of
sulphide within the main ore assemblage and is therefore
distinct from the known base metal and precious metal
deposits in the district.
The strongly quartz, topaz, andalusite and white mica
altered host rocks show both coherent intrusive, volcani-
clastic and hydrothermal breccia textures in an interdigi-
tating breccia complex shown as the breccia facies unit in
Figure 2. This breccia facies unit is surrounded by weakly
to moderately altered coherent dacitic units and silt to sand
size volcaniclastic units that have an increased amount of
sulphides impregnation (Py, Po, Ccp, Sp and Mag). The
distribution of the Au-Te mineralization is within the brec-
cia facies unit and related to its margins. The deposit sits
spatially under one small, previously mined, massive sul-
phide, surface deposit.
Motivation
Data from 2012 to 2023 shows that Åkulla Kankberg
ore with higher sulphur grades tends to have lower gold
recovery in flotation concentrates. Figure 3 illustrates the
correlation between gold recovery and the gold grade of the
ore fed into the plant. These findings suggest benefits from
using more selective flotation chemicals against sulphide
minerals, leading to laboratory and industrial-scale investi-
gations on their impact on recovery performance.
Mineral characterization studies were crucial in gaining
a better understanding of the relationship between Au-Te-Ag
minerals and sulphides, assisting in more informed deci-
sions in the ore treatment process. Additionally, the moti-
vation for reducing mass in the final flotation concentrate
aimed to increase gold production capacity in ore processing
Figure 1. Top View of the Boliden Concentrator
Figure 2. Cross-section of Åkulla Au-Te deposit (modified
from Nordfeldt et al 2019), in the Kankberg mine, looking
south, showing simplified geology, position of Au-Te
mineralization, and sulphide occurrences. Alteration rock is
dominated by intense quartz-sericite (±chlorite) alteration.
Coordinates are in SWEREF99
while B and C are used for ore processing. The B and C
lines consist of primary AG mill and secondary pebble
mill. Grinding circuit includes screens, from which coarse
material is sent to the primary mill while fines are sent to
a hydrocyclone battery. A part of screens underflow passes
through a gravimetric Knelson separator. Underflow from
cyclones is sent to the pebble mill via a flash flotation cell,
while fines are sent to flotation.
The B and C flotation lines consist of three circuits:
Cu/Pb-flotation, Cu/Pb-separation, and Zn-flotation. The
Kankberg Au-tellurium ore is typically processed on the C
line utilizing the Cu/Pb-flotation circuit, consisting of five
rougher flotation cells and four scavenger cells, followed
by four cleaner cells. Collectors PAX (74% potassium iso-
pentyl xanthate, 17% potassium methyl-butyl xanthate)
and Hostaflot 7869 (30–50% dithiophosphate, 25–30%
thiocarbamate) are used, with Dowfroth 250 (glycol) as the
frother. Sodium bisulfite is added for pH control and to
benefit Au-minerals flotation. Flotation tails are directed
to the CIL plant, while the Au-Te-concentrate undergoes
batch cyanide leaching at 65 °C. Figure 1 provides a top
view of the Boliden Concentrator, illustrating the three dis-
tinct circuit lines.
Geology
The Åkulla Kankberg ore is mined from the Åkulla Au-Te
mineralisation, a mineralogically distinct and newly recog-
nized ore deposit style in the Skellefteå District (Nordfeldt
et al. 2019). The mineralisation is characterized by the
abundance of topaz-quartz alteration, occurrence of anda-
lusite, white mica, Au-Te enrichments, and a paucity of
sulphide within the main ore assemblage and is therefore
distinct from the known base metal and precious metal
deposits in the district.
The strongly quartz, topaz, andalusite and white mica
altered host rocks show both coherent intrusive, volcani-
clastic and hydrothermal breccia textures in an interdigi-
tating breccia complex shown as the breccia facies unit in
Figure 2. This breccia facies unit is surrounded by weakly
to moderately altered coherent dacitic units and silt to sand
size volcaniclastic units that have an increased amount of
sulphides impregnation (Py, Po, Ccp, Sp and Mag). The
distribution of the Au-Te mineralization is within the brec-
cia facies unit and related to its margins. The deposit sits
spatially under one small, previously mined, massive sul-
phide, surface deposit.
Motivation
Data from 2012 to 2023 shows that Åkulla Kankberg
ore with higher sulphur grades tends to have lower gold
recovery in flotation concentrates. Figure 3 illustrates the
correlation between gold recovery and the gold grade of the
ore fed into the plant. These findings suggest benefits from
using more selective flotation chemicals against sulphide
minerals, leading to laboratory and industrial-scale investi-
gations on their impact on recovery performance.
Mineral characterization studies were crucial in gaining
a better understanding of the relationship between Au-Te-Ag
minerals and sulphides, assisting in more informed deci-
sions in the ore treatment process. Additionally, the moti-
vation for reducing mass in the final flotation concentrate
aimed to increase gold production capacity in ore processing
Figure 1. Top View of the Boliden Concentrator
Figure 2. Cross-section of Åkulla Au-Te deposit (modified
from Nordfeldt et al 2019), in the Kankberg mine, looking
south, showing simplified geology, position of Au-Te
mineralization, and sulphide occurrences. Alteration rock is
dominated by intense quartz-sericite (±chlorite) alteration.
Coordinates are in SWEREF99