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Gangue Rejection Strategies for Halleck Creek
Allanite Beneficiation
Greg Henderson
Wood Australia Pty Ltd
ABSTRACT: Rare earths production currently relies on exploitation of high grade bastnaesite and monazite
resources. However, discovery of such deposits is becoming less frequent and their locations often come with
high sovereign risk which deters investment. Development of alternative styles of mineralisation in lower risk
settings is becoming increasingly important to secure future rare earths supply. North America hosts large low
grade orebodies with the rare earth orthosilicate mineral allanite that is often difficult to physically upgrade due
to competing gangue minerals that have similar physical properties, in particular paramagnetic hornblende and
pyroxenes. This paper focusses on strategies investigated for separation of the hornblende mineral hastingsite
from allanite for American Rare Earth Limited’s Halleck Creek Project in Wyoming, in order to produce a
viable concentrate for downstream processing. Strategies evaluated include WHIMS, tabling, high G gravity
concentration, electrostatic separation and flotation. Electrostatic separation in particular shows significant
promise in separating these minerals, justifying further work. A conceptual flowsheet incorporating this concept
was developed as an outcome of testwork.
Keywords: rare earth elements, allanite, hastingsite, magnetic separation, beneficiation.
INTRODUCTION
This paper describes investigations into physical separa-
tion properties of allanite from associated gangue min-
erals, namely silica, non-ferrous feldspar minerals and
amphiboles, principally the hornblende hastingsite, for an
ore composite from the Halleck Creek Rare Earth Project
located 30 km southwest of Wheatlands, Wyoming USA,
being developed by American Rare Earths (ARR). The pri-
mary focus was on the use of wet high intensity magnetic
separation (WHIMS) for primary separation in conjunc-
tion with further upgrading strategies—gravity separation
(Falcon C and Wilfley table), flotation (both direct and
reverse) and electrostatic separation to achieve sufficient
upgrade of REE values for hydrometallurgical processing.
Rare earths at Halleck Creek are associated with alla-
nite, a sorosilicate mineral within the broader epidote group.
Host rocks consist of four rock units—fayalite monzonite
(FM), clinopyroxene quartz monzonite (CQM), biotite-
hornblende quartz syenite (BHS) and Red Mountain gran-
ite (RMG). ARR has published an estimated resource of
1.43 Bt at a grade of 0.33% TREO and an average NdPr
grade of 734 ppm (ARR, 2022). Whilst the grade of the
resource is substantially lower than many other rare earth
projects in various stages of development, its mineral assem-
blage is relatively simple and large resource size potentially
offers a long life project.
Primary allanite orebodies have not been economically
exploited, though a number of projects contain allanite as
a secondary or accessory rare mineral, including Nolans
Gangue Rejection Strategies for Halleck Creek
Allanite Beneficiation
Greg Henderson
Wood Australia Pty Ltd
ABSTRACT: Rare earths production currently relies on exploitation of high grade bastnaesite and monazite
resources. However, discovery of such deposits is becoming less frequent and their locations often come with
high sovereign risk which deters investment. Development of alternative styles of mineralisation in lower risk
settings is becoming increasingly important to secure future rare earths supply. North America hosts large low
grade orebodies with the rare earth orthosilicate mineral allanite that is often difficult to physically upgrade due
to competing gangue minerals that have similar physical properties, in particular paramagnetic hornblende and
pyroxenes. This paper focusses on strategies investigated for separation of the hornblende mineral hastingsite
from allanite for American Rare Earth Limited’s Halleck Creek Project in Wyoming, in order to produce a
viable concentrate for downstream processing. Strategies evaluated include WHIMS, tabling, high G gravity
concentration, electrostatic separation and flotation. Electrostatic separation in particular shows significant
promise in separating these minerals, justifying further work. A conceptual flowsheet incorporating this concept
was developed as an outcome of testwork.
Keywords: rare earth elements, allanite, hastingsite, magnetic separation, beneficiation.
INTRODUCTION
This paper describes investigations into physical separa-
tion properties of allanite from associated gangue min-
erals, namely silica, non-ferrous feldspar minerals and
amphiboles, principally the hornblende hastingsite, for an
ore composite from the Halleck Creek Rare Earth Project
located 30 km southwest of Wheatlands, Wyoming USA,
being developed by American Rare Earths (ARR). The pri-
mary focus was on the use of wet high intensity magnetic
separation (WHIMS) for primary separation in conjunc-
tion with further upgrading strategies—gravity separation
(Falcon C and Wilfley table), flotation (both direct and
reverse) and electrostatic separation to achieve sufficient
upgrade of REE values for hydrometallurgical processing.
Rare earths at Halleck Creek are associated with alla-
nite, a sorosilicate mineral within the broader epidote group.
Host rocks consist of four rock units—fayalite monzonite
(FM), clinopyroxene quartz monzonite (CQM), biotite-
hornblende quartz syenite (BHS) and Red Mountain gran-
ite (RMG). ARR has published an estimated resource of
1.43 Bt at a grade of 0.33% TREO and an average NdPr
grade of 734 ppm (ARR, 2022). Whilst the grade of the
resource is substantially lower than many other rare earth
projects in various stages of development, its mineral assem-
blage is relatively simple and large resource size potentially
offers a long life project.
Primary allanite orebodies have not been economically
exploited, though a number of projects contain allanite as
a secondary or accessory rare mineral, including Nolans