XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1229
87% of allanite is classified as liberated and another 8.4%
high grade middlings. The unliberated allanite is strongly
associated with hastingsite, the dominant gangue mineral.
The preceding analysis demonstrates that allanite is
highly liberated in cleaner WHIMS magnetics and the only
impediment to achieve a high-grade allanite concentrate is
overcoming the challenges represented by the similarities in
physical properties of hastingsite and allanite.
Gravity Concentration
Heavy Liquid Separation (HLS)
HLS analysis was performed on cleaner WHIMS magnet-
ics to assess potential for separation. SG increments of 0.2
were applied for a separation range of 3.0 to 3.8. Figure 9
provides a comparison of sinks grades by SG partition. A
high degree of enrichment in the 3.6 to 3.8 SG fraction
occurred (7.9% TREE+Y grade) for a recovery of 42.6%,
which suggests much of the free REE mineralised allanite is
concentrated in this fraction.
This supports earlier observations that the allanite is
towards the lower end of published SG data for allanite (3.6
to 4.3). Recovery of Fe to this fraction is somewhat lower
at 6.8% for a grade of 20.9%, compared with 13.8% Fe
in grains in liberated allanite reported from EPMA analy-
sis. This indicates little of the hastingsite is in this fraction
as its iron content is close to 30%. The +3.8 SG fraction
is also enriched though not to the same extent (2.59%
TREO+Y grade) for an additional 12.4% recovery, a total
of 55% recovery for the two densest fractions, in a total
of 13.6% mass yield relative to the test feed. Iron is con-
centrated in the 3.2 to 3.6 SG range, typically inside the
published SG range of 3.2 to 3.5 for hastingsite generally
resides. Interpolation of results indicates a partition SG of
3.5 would theoretically yield a “sinks” of 7% mass relative
to new feed at 4% TREO grade and 72.2% stage recovery,
or 50% of new feed.
Dense media separation (DMS) has potential as a pre-
concentration step but it is important to ensure that feed of
a size 0.5 mm or coarser is considered rather than directly
scaling up from HLS results to industrial sized dense media
cyclone systems. This is to ensure that there is sufficient sep-
aration between the dense media particle size distribution
and that of the DMS feed so as to ensure effective recovery
of media after DMS treatment.
Figure 8. Cleaner WHIMS magnetics mineral abundance
87% of allanite is classified as liberated and another 8.4%
high grade middlings. The unliberated allanite is strongly
associated with hastingsite, the dominant gangue mineral.
The preceding analysis demonstrates that allanite is
highly liberated in cleaner WHIMS magnetics and the only
impediment to achieve a high-grade allanite concentrate is
overcoming the challenges represented by the similarities in
physical properties of hastingsite and allanite.
Gravity Concentration
Heavy Liquid Separation (HLS)
HLS analysis was performed on cleaner WHIMS magnet-
ics to assess potential for separation. SG increments of 0.2
were applied for a separation range of 3.0 to 3.8. Figure 9
provides a comparison of sinks grades by SG partition. A
high degree of enrichment in the 3.6 to 3.8 SG fraction
occurred (7.9% TREE+Y grade) for a recovery of 42.6%,
which suggests much of the free REE mineralised allanite is
concentrated in this fraction.
This supports earlier observations that the allanite is
towards the lower end of published SG data for allanite (3.6
to 4.3). Recovery of Fe to this fraction is somewhat lower
at 6.8% for a grade of 20.9%, compared with 13.8% Fe
in grains in liberated allanite reported from EPMA analy-
sis. This indicates little of the hastingsite is in this fraction
as its iron content is close to 30%. The +3.8 SG fraction
is also enriched though not to the same extent (2.59%
TREO+Y grade) for an additional 12.4% recovery, a total
of 55% recovery for the two densest fractions, in a total
of 13.6% mass yield relative to the test feed. Iron is con-
centrated in the 3.2 to 3.6 SG range, typically inside the
published SG range of 3.2 to 3.5 for hastingsite generally
resides. Interpolation of results indicates a partition SG of
3.5 would theoretically yield a “sinks” of 7% mass relative
to new feed at 4% TREO grade and 72.2% stage recovery,
or 50% of new feed.
Dense media separation (DMS) has potential as a pre-
concentration step but it is important to ensure that feed of
a size 0.5 mm or coarser is considered rather than directly
scaling up from HLS results to industrial sized dense media
cyclone systems. This is to ensure that there is sufficient sep-
aration between the dense media particle size distribution
and that of the DMS feed so as to ensure effective recovery
of media after DMS treatment.
Figure 8. Cleaner WHIMS magnetics mineral abundance