Mr. Mark Saxon reports
TASMAN ADVANCES MINERAL PROCESSING AT NORRA KARR, SWEDEN
Tasman Metals Ltd. has provided an update on recent process
optimization results from expanded metallurgical testing at the
company's 100-per-cent-owned Norra Karr heavy rare earth element/zirconium project in Sweden. Test work was completed in Germany
by Anzaplan (Dorfner Analysenzentrum und Anlagenplanungsgesellschaft
mbH), a member of the Dorfner group of companies, Germany's leading
supplier of industrial minerals.
High recovery of rare earth elements in a low mass during combined flotation/magnetic
separation tests, including 82.5 per cent yttrium oxide (Y2O3) and 76.9 per cent total rare earth oxide (TREO) recovered in only 25.2 per cent of the
High recovery of rare earth elements in magnetic separation tests on three major ore
types from Norra Karr;
Eudialyte confirmed as the only rare-earth-element-bearing mineral present in more than
trace abundance in all ore types;
All major ore types shown to be mineralogically indistinguishable when
ground to 500 microns, suggesting geological variation across the orebody is unlikely to affect processing behaviour;
Flotation test work very successful in separating aegirine from
eudialyte using commercial reagent;
Low-iron nepheline/feldspar fraction identified as potential byproduct.
Mark Saxon, president and chief executive officer, stated:
"The effectiveness of the current optimization tests for combined
magnetic and flotation techniques by Anzaplan give us confidence that
further research will enable a high-recovery/low-mass mineral
concentrate to be produced from Norra Karr ore. Our metallurgical research is a continuous
process, with facilities in Europe and North America working to further
optimize the flow sheet. Data generated by Anzaplan will be a key part
of our upcoming prefeasibility study and pilot plant tests."
Three bulk samples totalling approximately 1.2 tonnes were supplied to
Anzaplan, representing the two major (pegmatitic grennaite and migmatitic grennite) and one minor ore type (grennaite) that comprise the Norra Karr resource. Each sample was
composited from drill core collected across the deposit and is
considered very representative. All previous metallurgical testing was
performed on blended material combining all ore types. Mineralogical
character and metallurgical behaviour of each ore type were tested to
constrain future processing considerations. Geochemical character of
each ore type based on drilling information is shown in the attached table.
SUMMARY OF PRINCIPAL ORE TYPE GEOCHEMISTRY FROM AVERAGE DRILLING DATA
TREO HREO/TREO ZrO2 Dy2O3 Y2O3 Tb2O3 Nd2O3
(%) (%) (%) (ppm) (ppm) (ppm) (ppm)
PGT (pegmatitic grennaite) 0.614 54.7 2.00 289 2300 42 662
GTM (migmatitic grennite) 0.490 45.0 1.52 184 1506 27 563
GTC (grennaite) 0.261 63.5 1.33 152 1056 20 233
- TREO (total rare earth oxide) refers to the sum of La2O3, Ce2O3, Pr2O3, Nd2O3,
Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3 and Y2O3.
- HREO (heavy rare earth oxide) refers to sum of Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3,
Er2O3, Tm2O3, Yb2O3, Lu2O3 and Y2O3.
- The most significant rare earth oxides by percentage are Y2O3, La2O3, Ce2O3,
Nd2O3 and Dy2O3.
Mineral liberation analysis (MLA) was completed on 15 samples to
identify mineralogy and liberation trends at a range of grain sizes.
MLA demonstrated that once crushed to 500 microns (0.5 millimetre) or less,
based on the range and relative distribution of minerals present, all
three ore types are indistinguishable. The principal rare-earth-element-bearing
mineral at Norra Karr is eudialyte in all ore types, which has a modal
abundance of 7.8 per cent and 6.7 per cent in the major ore types pegmatitic grennaite and migmatitic grennite,
respectively. This simplicity and homogeneity of ore is
very encouraging, suggesting geological variation is unlikely to
significantly influence metallurgical processing.
Consistent with previous research is the very low abundance of
unidentified other minerals, at 2.4 per cent or less, in all three ore
types. While most REE projects display a complex range of REE-bearing
minerals, rare earth elements at Norra Karr are virtually entirely hosted by
eudialyte, minimizing complexity in the processing flow sheet.
As eudialyte is soft relative to other mineral phases in the rock; MLA
also highlighted that it reports with greater abundance in the finer
grind fractions. The additional sample from Norra Karr is now with
grinding equipment suppliers to test and optimize sizing behaviour under
various grind conditions.
Mineral concentrate tests
A range of mineral concentrate preparation tests were run by Anzaplan,
based on the previously reported results achieved by the Geological
Survey of Finland (GTK) in 2011. The aim was to produce a mineral
concentrate containing most or all of the eudialyte (so achieving high
recovery), while discarding most of the unmineralized gangue material
(so achieving low sample mass). Tests were run in parallel on the
different ore types; however, no significant variation in results by ore
type were observed. While magnetic separation and flotation were the
focus of research, gravity, electrostatic and centrifuge methods were
also applied, each of which achieved only poor eudialyte separation.
Due to the paramagnetic behaviour of eudialyte, magnetic separation
performed very well under non-optimized conditions. Numerous tests
were completed, which demonstrated the excellent magnetic extractability
of both eudialyte and a common iron-bearing mineral aegirine. Review of
external publications suggest aegirine is not soluble under the acid
conditions considered for hydrometallurgical processing of Norra Karr
ore, and shall therefore be inert in a rare earth element leach circuit. Example
recoveries achieved with single pass (not recirculated) WHIMS (wet,
high-intensity magnetic separation) using the minus-100-micron fraction of
representative Nora Karr ore are shown in the attached table.
Tasman is now focused on further improving the eudialyte concentrate
quality by multiple-stage magnetic separation and regrinding methods
that were successfully tested by GTK in earlier bench-scale tests.
RECOVERY ASSOCIATED WITH MAGNETIC SEPARATION
TREO ZrO2 Fe2O3
Mass recovery recovery recovery
fraction 53% 97% 71% 99%
fraction 23% 80% 41% 91%
Extensive flotation testing was also completed by Anzaplan. While
eudialyte does not appear amenable to efficient direct flotation, a
commercially available flotation reagent at near-neutral pH was shown
to be extremely effective in the selective removal of aegirine from
Aegirine is three times more abundant than eudialyte in typical ore
samples; therefore, its removal greatly reduces the mass of the magnetic
fraction. Non-optimized test results indicate that approximately two-thirds of the aegirine can be removed from the crushed sample prior to
magnetic separation at a TREO recovery of 88 per cent. Removal of this material
prior to magnetic separation significantly improves quality of the
eudialyte concentrate, with only a small loss of REE.
Combined flotation and magnetic separation
Furthermore, Anzaplan has tested various scenarios combining flotation
and magnetic separation. One such combination proved extremely
effective, where recovery for the total process was 82.2 per cent of the yttrium oxide, 76.9 per cent of the TREO and 49.7 per cent ZrO2 in only 25.2 per cent of the mineral mass. Recovery of other heavy REEs (Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)
mirrors the recovery of Y2O3 in flotation and magnetic separation tests.
The relationship between flotation and magnetic separation, and the
impact on operating and capital costs is now the subject of continuing research. A concentrate sample produced by flotation and magnetic
separation has been supplied to a research partner for additional
hydrometallurgical leach testing.
Minor research was also carried out by Anzaplan on the byproduct
materials. While significant work remains to be undertaken, the
feldspar/nepheline product removed as the non-magnetic fraction
during magnetic separation has a bulk chemistry and sufficiently low
iron content, in line with the requirements of various European glass
Tasman's 100-per-cent-owned Norra Karr project is the only National Instrument 43-101-compliant
rare earth element resource in mainland Europe. Norra Karr lies 15 kilometres north-northeast of the
township of Granna and 300 kilometres southwest of the capital, Stockholm, in mixed
forestry and farming land. The short time taken from discovery to mining lease application demonstrates the efficiency and advantage of operating in a
jurisdiction with a strong and transparent mining act and a long-term
association with resource industries. The project is proximal to road,
rail, power and operating ports, plus skilled personnel, minimizing the
need for off-site infrastructure to be built by the company.
Norra Karr is one of the largest and most economically robust projects
amongst its peers, due to the high contribution of the high-value
critical rare earth elements (dysprosium, yttrium, neodymium and terbium). Substantial capital and operating cost benefits are provided by
the existing infrastructure and the simple mineralogy that allows
ambient temperature and pressure processing. Norra Karr's proximity
and easy road access to European markets stands as a unique operating
advantage for the project.
Samples associated with this test work were analyzed at the laboratory
of Anzaplan in Hirschau, Germany, an ISO 9001:2000-accredited facility,
where duplicates, repeats, blanks and known standards were inserted
according to standard industry practice. Tasman provided registered
standards produced from Norra Karr material as further quality assurance/quality control. The
qualified person for the company's exploration projects, Mr. Saxon,
president and chief executive officer of Tasman, and a member of the
Australasian Institute of Mining and Metallurgy and Australian
Institute of Geoscientists, has reviewed and verified the contents of
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