2380 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
flotation properties of telluride minerals is essential for
improving the recovery of tellurium and other valuables
such as gold, silver and copper. This in turn gives insight
into the separation of a telluride flotation product suitable
for conversion to pure tellurium.
Telluride Flotation
Extensive work has been completed on the flotation of
gold, gold-silver alloys and gold ores however there is a lack
of information detailing the difference between flotation of
native gold and other gold minerals (Allan &Woodcock,
2001 Dunne, 2016 Ellis &Deschênes, 2016).
Preliminary single mineral studies have previously been
conducted on calaverite (AuTe2) and sylvanite (AuAgTe4)
(Lu &Lawson, 1994 Padmanaban &Lawson, 1991). The
results indicated the use of copper sulphate as an activa-
tor improved recoveries for shorter chain xanthates. The
studies also indicated that flotation recovery with xanthate
increased with increasing chain length.
A study conducted by Yan and Hariyasa (1997) exam-
ined the impact of collector type, collector dosage and pH
on a high grade Kalgoorlie mixed telluride ore. The study
found telluride minerals float readily in the laboratory with
the addition of frother only. The study also found the use
of xanthate alone decreased telluride recovery and that the
addition of copper sulphate as an activator with xanthate
improved telluride recovery (Yan &Hariyasa, 1997). No
mechanism for this phenomenon was presented.
Telluride minerals have also demonstrated natural
floatability on an industrial scale using only a frothing
agent (Colbert, 1980 Johnston, 1933 Singh, 1956). The
Emperor Mine in Vatukoula, Fiji utilised the natural flota-
tion properties of telluride minerals to remove a high grade
gold telluride concentrate prior to pyrite flotation. The tel-
luride concentrate was then leached to extract gold and tel-
lurium (Cornwall &Hisshion, 1976).
The surface of calaverite was confirmed by Jin (Jin,
2016) to exhibit relatively strong hydrophobicity. The mea-
sured contact angle for calaverite (001 surface) was found
to be 80 degrees (Jin, 2016), similar to that for molybde-
nite (face) at 80 degrees (Chander &Fuerstenau, 1972).
The natural floatability of molybdenite is well known and
is attributed to the layered crystal structure of the mineral
(Castro et al., 2016). Calaverite is also classified as a layered
mineral however does not exhibit the preferential break-
age or cleavage exhibited by molybdenite (Hulliger, 2012).
Molybdenite is recovered from porphyry sulphide ores
by flotation with neutral oils, such as kerosene and diesel
(Song et al., 2012 Yi et al., 2021).The use of neutral oils on
fine telluride recovery is included in this study.
Mineral Samples
Isolating naturally occurring gold and silver telluride min-
erals from ores in significant quantity is a difficult and
impractical task. Telluride minerals obtained from flotation
plant concentrates are undesirable due to surface altera-
tion by flotation reagents. Previous studies on platinum
tellurides have shown that flotation performance of tested
synthetic telluride minerals was adequate when compared
with that for natural ores (Shamaila &O’Connor, 2008).
This study utilises synthetic minerals to indicate the perfor-
mance of naturally occurring minerals.
The high density and brittle nature of telluride min-
erals, such as calaverite and hessite, often results in over-
grinding in comminution circuits (Ellis &Deschênes,
2016 Johnston, 1933). This is seen in laboratory test work
conducted on Kalgoorlie ores where up to 40% of the tel-
lurium was finer than 5 micron (Weller et al., 1998). The
fine nature of the telluride minerals in flotation feed makes
the flotation performance of fine and ultrafine calaverite
and hessite highly relevant to current processing circuits.
This study will be focussing on the flotation performance
of minus 25 micron material.
EXPERIMENTAL
Synthesis of Telluride Minerals
Synthetic hessite and calaverite were prepared using a
method developed during this project. Stoichiometric
amounts of high grade tellurium powder and silver pow-
der or gold leaf were combined and compressed into pel-
lets. The pellets were transferred to borosilicate glass tubes,
flushed with nitrogen and sealed under vacuum. The tubes
were placed in an oven for an initial period of 8 hours at
500°C then removed and cooled. The sample was ground
with an agate mortar and pestle before being pelletised,
sealed in a borosilicate tube under vacuum and heated for
2 hours at 450°C (calaverite) or 500°C (hessite). The grind/
pelletise/heat cycle was repeated for at least 5 cycles.
Examination of the mineral samples by XRD (Olympus
BTX II) confirmed hessite and calaverite were the primary
phases present in the respective samples (90%). Polished
sections were reviewed by Zeiss optical microscope to check
for consistency across the pellets. The sections indicated a
uniform product with minor unreacted metallic gold (cala-
verite) and silver (hessite) evident.
Unground samples were stored under vacuum in sealed
borosilicate tubes until required. Mineral samples were
ground for test work using an agate mortar and pestle and
dry sieved at 25 microns. Residual metallic particles in the
mineral samples were removed during the sieving process.
flotation properties of telluride minerals is essential for
improving the recovery of tellurium and other valuables
such as gold, silver and copper. This in turn gives insight
into the separation of a telluride flotation product suitable
for conversion to pure tellurium.
Telluride Flotation
Extensive work has been completed on the flotation of
gold, gold-silver alloys and gold ores however there is a lack
of information detailing the difference between flotation of
native gold and other gold minerals (Allan &Woodcock,
2001 Dunne, 2016 Ellis &Deschênes, 2016).
Preliminary single mineral studies have previously been
conducted on calaverite (AuTe2) and sylvanite (AuAgTe4)
(Lu &Lawson, 1994 Padmanaban &Lawson, 1991). The
results indicated the use of copper sulphate as an activa-
tor improved recoveries for shorter chain xanthates. The
studies also indicated that flotation recovery with xanthate
increased with increasing chain length.
A study conducted by Yan and Hariyasa (1997) exam-
ined the impact of collector type, collector dosage and pH
on a high grade Kalgoorlie mixed telluride ore. The study
found telluride minerals float readily in the laboratory with
the addition of frother only. The study also found the use
of xanthate alone decreased telluride recovery and that the
addition of copper sulphate as an activator with xanthate
improved telluride recovery (Yan &Hariyasa, 1997). No
mechanism for this phenomenon was presented.
Telluride minerals have also demonstrated natural
floatability on an industrial scale using only a frothing
agent (Colbert, 1980 Johnston, 1933 Singh, 1956). The
Emperor Mine in Vatukoula, Fiji utilised the natural flota-
tion properties of telluride minerals to remove a high grade
gold telluride concentrate prior to pyrite flotation. The tel-
luride concentrate was then leached to extract gold and tel-
lurium (Cornwall &Hisshion, 1976).
The surface of calaverite was confirmed by Jin (Jin,
2016) to exhibit relatively strong hydrophobicity. The mea-
sured contact angle for calaverite (001 surface) was found
to be 80 degrees (Jin, 2016), similar to that for molybde-
nite (face) at 80 degrees (Chander &Fuerstenau, 1972).
The natural floatability of molybdenite is well known and
is attributed to the layered crystal structure of the mineral
(Castro et al., 2016). Calaverite is also classified as a layered
mineral however does not exhibit the preferential break-
age or cleavage exhibited by molybdenite (Hulliger, 2012).
Molybdenite is recovered from porphyry sulphide ores
by flotation with neutral oils, such as kerosene and diesel
(Song et al., 2012 Yi et al., 2021).The use of neutral oils on
fine telluride recovery is included in this study.
Mineral Samples
Isolating naturally occurring gold and silver telluride min-
erals from ores in significant quantity is a difficult and
impractical task. Telluride minerals obtained from flotation
plant concentrates are undesirable due to surface altera-
tion by flotation reagents. Previous studies on platinum
tellurides have shown that flotation performance of tested
synthetic telluride minerals was adequate when compared
with that for natural ores (Shamaila &O’Connor, 2008).
This study utilises synthetic minerals to indicate the perfor-
mance of naturally occurring minerals.
The high density and brittle nature of telluride min-
erals, such as calaverite and hessite, often results in over-
grinding in comminution circuits (Ellis &Deschênes,
2016 Johnston, 1933). This is seen in laboratory test work
conducted on Kalgoorlie ores where up to 40% of the tel-
lurium was finer than 5 micron (Weller et al., 1998). The
fine nature of the telluride minerals in flotation feed makes
the flotation performance of fine and ultrafine calaverite
and hessite highly relevant to current processing circuits.
This study will be focussing on the flotation performance
of minus 25 micron material.
EXPERIMENTAL
Synthesis of Telluride Minerals
Synthetic hessite and calaverite were prepared using a
method developed during this project. Stoichiometric
amounts of high grade tellurium powder and silver pow-
der or gold leaf were combined and compressed into pel-
lets. The pellets were transferred to borosilicate glass tubes,
flushed with nitrogen and sealed under vacuum. The tubes
were placed in an oven for an initial period of 8 hours at
500°C then removed and cooled. The sample was ground
with an agate mortar and pestle before being pelletised,
sealed in a borosilicate tube under vacuum and heated for
2 hours at 450°C (calaverite) or 500°C (hessite). The grind/
pelletise/heat cycle was repeated for at least 5 cycles.
Examination of the mineral samples by XRD (Olympus
BTX II) confirmed hessite and calaverite were the primary
phases present in the respective samples (90%). Polished
sections were reviewed by Zeiss optical microscope to check
for consistency across the pellets. The sections indicated a
uniform product with minor unreacted metallic gold (cala-
verite) and silver (hessite) evident.
Unground samples were stored under vacuum in sealed
borosilicate tubes until required. Mineral samples were
ground for test work using an agate mortar and pestle and
dry sieved at 25 microns. Residual metallic particles in the
mineral samples were removed during the sieving process.
