2629
Selective Recovery of Scheelite from an Archetypal Tungsten
Skarn Using Amine and Fatty-Acid Flotation
Y. Foucaud, C. Korbel, O. Gamba, M. Auch-Roy, A. Vanderbruggen, F. Diot
Université de Lorraine, CNRS, GeoRessources, Nancy, France
ABSTRACT: Skarns today represent around 50% of the global tungsten reserves. Considering their fine textures
and the trend of scheelite to form fine particles during the milling stage, the use of froth flotation is mandatory
for their processing. However, tungsten skarns generally contain significant amounts of calcium minerals such
as fluorite, apatite, and calcite, which entail a problem of selectivity in the flotation stage. Here, we show that
scheelite surfaces are negatively charged above pH 2 while fluorite surfaces are positively charged below pH 5.
Then, we combine an amine-based and a fatty-acid-based room temperature flotation stages to reject fluorite on
a Portuguese archetype of tungsten skarns. We use the design of experiments methodology to optimize the pH
and the dosages in depressants and amine, to maximize the scheelite recovery and the rejection of the calcium
salts. Despite the poor floatability of scheelite using amines, a recovery of 70% and a good rejection of gangue
minerals is attained in the amine flotation stage.
INTRODUCTION
For more than a decade, tungsten has been classified as a
critical raw material by the European Union and the United
States (European Commission, 2010 U.S. Department
of the Interior, 2018). This was induced not only by the
high economic importance of tungsten, which is consid-
erably used in the automotive, aeronautics, and defense
industries, but also by the monopoly of China on the tung-
sten world production, causing a strong insecurity on the
tungsten supply (U.S. Geological Survey, 2019). For more
than 30 years, China has dominated global tungsten pro-
duction, contributing, for instance, over 80% of the total
82,000 tons produced worldwide in 2022 (U.S. Geological
Survey, 2019). China hosts more than ten major tungsten
mines, each with an annual output exceeding 1,300 tons of
WO3, primarily concentrated in southern China (Audion
and Labbé, 2012 Pitfield et al., 2011 Werner et al., 1998
Yang, 2018). The Xianglushan and Shizhuyuan deposits,
specifically, stand out as the two largest tungsten mines in
China, producing over 5,700 and 5,500 tons of WO3 each
year, respectively (Yang, 2018). Several other countries,
including Vietnam, Russia, and a few European nations,
contribute smaller quantities of tungsten. Vietnam oper-
ates the Nui Phao mine, one of the world’s largest tungsten
mines, with estimated reserves of 66 million tons of ore
averaging 0.2% WO3 (Masan Resources, 2012). Russia has
been extracting tungsten from the Vostok 2 sulphide schee-
lite skarn ore since 1969, with approximately 1 million tons
of remaining ore boasting a high average grade of around
1.7% WO3 (Soloviev and Krivoshchekov, 2011). Despite
the decline in tungsten prices during the 1980s, Austria and
Portugal managed to keep the Mittersill and Panasqueira
mines operational. In 2018, they produced 980 tons and
770 tons of tungsten, respectively, representing a minor
fraction of global production. Notably, the significant
increase in tungsten prices in the mid-2000s led to the
Selective Recovery of Scheelite from an Archetypal Tungsten
Skarn Using Amine and Fatty-Acid Flotation
Y. Foucaud, C. Korbel, O. Gamba, M. Auch-Roy, A. Vanderbruggen, F. Diot
Université de Lorraine, CNRS, GeoRessources, Nancy, France
ABSTRACT: Skarns today represent around 50% of the global tungsten reserves. Considering their fine textures
and the trend of scheelite to form fine particles during the milling stage, the use of froth flotation is mandatory
for their processing. However, tungsten skarns generally contain significant amounts of calcium minerals such
as fluorite, apatite, and calcite, which entail a problem of selectivity in the flotation stage. Here, we show that
scheelite surfaces are negatively charged above pH 2 while fluorite surfaces are positively charged below pH 5.
Then, we combine an amine-based and a fatty-acid-based room temperature flotation stages to reject fluorite on
a Portuguese archetype of tungsten skarns. We use the design of experiments methodology to optimize the pH
and the dosages in depressants and amine, to maximize the scheelite recovery and the rejection of the calcium
salts. Despite the poor floatability of scheelite using amines, a recovery of 70% and a good rejection of gangue
minerals is attained in the amine flotation stage.
INTRODUCTION
For more than a decade, tungsten has been classified as a
critical raw material by the European Union and the United
States (European Commission, 2010 U.S. Department
of the Interior, 2018). This was induced not only by the
high economic importance of tungsten, which is consid-
erably used in the automotive, aeronautics, and defense
industries, but also by the monopoly of China on the tung-
sten world production, causing a strong insecurity on the
tungsten supply (U.S. Geological Survey, 2019). For more
than 30 years, China has dominated global tungsten pro-
duction, contributing, for instance, over 80% of the total
82,000 tons produced worldwide in 2022 (U.S. Geological
Survey, 2019). China hosts more than ten major tungsten
mines, each with an annual output exceeding 1,300 tons of
WO3, primarily concentrated in southern China (Audion
and Labbé, 2012 Pitfield et al., 2011 Werner et al., 1998
Yang, 2018). The Xianglushan and Shizhuyuan deposits,
specifically, stand out as the two largest tungsten mines in
China, producing over 5,700 and 5,500 tons of WO3 each
year, respectively (Yang, 2018). Several other countries,
including Vietnam, Russia, and a few European nations,
contribute smaller quantities of tungsten. Vietnam oper-
ates the Nui Phao mine, one of the world’s largest tungsten
mines, with estimated reserves of 66 million tons of ore
averaging 0.2% WO3 (Masan Resources, 2012). Russia has
been extracting tungsten from the Vostok 2 sulphide schee-
lite skarn ore since 1969, with approximately 1 million tons
of remaining ore boasting a high average grade of around
1.7% WO3 (Soloviev and Krivoshchekov, 2011). Despite
the decline in tungsten prices during the 1980s, Austria and
Portugal managed to keep the Mittersill and Panasqueira
mines operational. In 2018, they produced 980 tons and
770 tons of tungsten, respectively, representing a minor
fraction of global production. Notably, the significant
increase in tungsten prices in the mid-2000s led to the