TSX: RES & NYSE AMEX: REE
- Pilot Plant testing of oxide resource begins
- Overall 80-85% recovery predicted from test program
- Further testing planned on oxide-carbonate and stockwork mineralization
- Initial testing of heavy rare earth-enriched mineralization to begin in
Q4.
LAKEWOOD, CO, Sept. 7, 2011 /CNW/ - Rare Element Resources Ltd. (TSX: RES and NYSE-AMEX: REE) (the
"Company") announces the completion of the bench-scale metallurgical test program
for near-surface, oxidized high-grade, rare earth-mineralized vein
material from the Bull Hill Deposit at the Bear Lodge project, Wyoming.
The test program resulted in the development of a process flowsheet
that will become the basis for a pilot plant operation and a
Preliminary Feasibility ("Pre-feasibility") Study. Additional studies
are also being conducted on the high-grade oxide-carbonate
mineralization type, and on the low-grade stockwork mineralization that
envelops the high-grade material. The pilot plant test is currently
underway to further define an economical ore process and to develop
design criteria that can be used to scale up to commercial operation.
Completion of the initial pilot plant testing is scheduled for the end
of October 2011. The low-grade stockwork mineralization (generally less
than 1.5% REO) surrounds the resource area and is not included in the
Company's NI 43-101 resource estimate (see news release of 14 June
2011). Much of this material will be mined in the current pit design in
order to access the high grade areas. These tests will determine
whether the low-grade rare-earth-element (REE) mineralization can be
upgraded and recovered from these areas in a simple cost effective
manner.
Bench-Scale High-grade Oxide Testing
Rare-earth mineralized bodies occur as high-grade dikes and veins within
the Bull Hill deposit. They include a well-defined, near-surface
oxidized zone that has been the subject of most metallurgical testing
to date. The oxide mineralization contains essentially no matrix
carbonates or sulfides. The sulfides are completely oxidized to hydrous
iron oxides, and the non-REE bearing carbonate minerals (calcite and
strontianite) are completely leached from the zone, which ranges from
the surface to depths of about 500 feet. These conditions created a
loose and friable oxide material that allows for a simple physical
mineral processing method.
In parts of the high-grade zone, the sulfides are oxidized but matrix
carbonate is partially and variably leached. This zone is termed the
"oxide-carbonate" zone. A thin "transitional zone" occurs at the base
of the oxide and/or oxide-carbonate zone at a depth of approximately
500 feet (150 m). The transitional zone passes relatively abruptly into
the sulfide-bearing zone with typical carbonatite characteristics.
Tests on the high-grade oxide mineralization indicate that recoveries of
80 to 85 percent of rare-earth oxides ("REO") are expected using a
two-stage process. The first stage is mineral concentration, also known
as physical upgrading ("PUG"). The second stage is a chemical leaching
process using hydrochloric acid that produces a mixed rare-earths
leachate that is precipitated as a bulk carbonate concentrate. The
series of bench-scale testing programs was completed by Mountain States
R&D International ("MSRDI"), Vail, Arizona, under the direction of Dr.
Roshan Bhappu. The test results show that 80-90 percent REO can be
recovered in 50-60 weight percent of the original mass weight by
employing a simple washing, scrubbing, and screening process that
produces a mineral pre-concentrate of sand-size and finer particles.
The washing and screening process uses only water as a process media
and is similar to gravel washing plants that are commonly employed
throughout the United States. Using a 5 to 8 percent REO head grade
sample, the pre-concentrate can be upgraded to 16-19 percent REO using
this process. A parallel series of tests to verify the process has been
conducted by Nagrom of Perth, Australia, under the direction of Mr.
Tony Wilkinson, General Manager.
Table 1. Mineral concentration by physical upgrading of high-grade oxide
material*
|
|
|
|
Sample | Weight | Assay | Distribution |
| % | % REO | % REO(Recovery) |
- 500 mesh
|
28.60
|
21.68
|
79.10
|
- 325 mesh
|
32.30
|
20.60
|
84.80
|
- 200 mesh
|
35.60
|
19.49
|
88.60
|
- 100 mesh
|
38.10
|
18.54
|
90.20
|
- 48 mesh
|
40.10
|
17.83
|
91.10
|
*Using a head grade of approximately 8% REO
The pre-concentrate will be trucked to a hydrometallurgical facility
located approximately 40 miles from the Bull Hill Mine site. The plant
site will be selected from several sites identified in the area that
are located on a railroad line with existing infrastructure. Such a
location will help reduce the environmental impact associated with
chemical processing.
The subsequent leaching process consists of dissolving the
pre-concentrate in a 15-17 percent hydrochloric acid leach solution at
a temperature of 90 degrees centigrade. This updated acid concentration
for leaching is a significant reduction from the 21 percent
concentration used in modeling costs in the Preliminary Economic
Assessment filed in November, 2010. In addition, the leach temperature
of 90 degrees is lower than many other REE leach projects and allows
for lower energy consumption.
Once the rare-earth minerals are dissolved, iron is precipitated using
sodium carbonate and sodium hydroxide. A mixed rare-earth carbonate
precipitate is produced by adding sodium carbonate to the rare-earth
leach solution. Approximately 95 percent of the REO in the
pre-concentrate is dissolved by the hydrochloric acid and recovered in
the precipitate, with an upgraded concentration of approximately 40
percent REO. Optimization of the leaching and precipitation process is
underway. The hydrochloric acid is regenerated in a distillation
circuit using sulfuric acid and sodium chloride. This regeneration
process is commonly used in the steel industry.
Table 2. Chemical concentration results from bench-scale leaching testwork
|
|
|
|
|
|
|
|
|
Sample:
| Ce2O3 | La2O3 | Nd2O3 | Pr2O3 | Sm2O3 | Y2O3 | REO | Fe |
| % | % | % | % | % | % | % | % |
Leach residue
|
0.35
|
1.06
|
0.63
|
0.19
|
0.11
|
0.01
|
2.35
|
1.81
|
Iron Precipitate
|
3.00
|
1.82
|
1.01
|
0.45
|
0.14
|
0.00
|
6.43
|
17.70
|
Mixed Carbonate Precipitate | 18.59 | 11.47 | 6.11 | 2.90 | 0.84 | 0.02 | 39.93 | 0.15 |
Pilot Plant Test Program of the High-Grade Oxide REE bulk sample
The following data are used as the basis for the pilot scale plant that
commenced in early September 2011. Hazen Research Inc., of Golden,
Colorado, is contracted to conduct pilot testing of this flowsheet.
Approximately 13 tons of high grade and stockwork mineralized material
will be processed over the next several months to develop data for the
pre-feasibility study and to support the on-going environmental
permitting process.
The design criteria and flowsheet for this upcoming pre-feasibility
study are as follows:
High Grade Feed Rate, stpd |
| 1,000 |
Grade, % REO |
| 3.5 - 6.0 |
Stockwork Feed Rate, stpd |
| 1,000 |
Grade, % REO |
| 0.5 - 1.5 |
Mass Reduction from PUG Plant, % |
|
|
High Grade |
| 30 - 50 |
Stockwork |
| 80 |
Feed Rate to Hydrometallurgical Plant, stpd |
| 400 - 500 |
Grade, % REO |
| 16-19 |
Hydrochloric Acid Concentration, % |
| 15 - 17 |
Carbonate Precipitation Rate, stpd |
| 80 - 100 |
Grade, % REO |
| 40 |
Figure 1. Metallurgical Flowsheet for Oxide Zone Mineralization of Bull Hill
Deposit.
Mineral concentration/physical upgrading followed by chemical
concentration/leaching.
http://files.newswire.ca/675/RareElementFlowsheet.jpg
Oxide-Carbonate Testing
The oxidized, but incompletely leached, oxide-carbonate zone in the Bull
Hill deposit generally occurs beneath the oxide zone, but may locally
breach the surface in select dikes and extend downward to the
transitional zone. It is characterized by an absence of sulfides, with
the residual iron oxides formed during the complete oxidation of the
former sulfide minerals, and by variable amounts of relict matrix
carbonates (calcite ± strontianite). As now defined, the transitional
zone is relatively flat-lying and occurs at depth as a thin layer
immediately above the sulfide-bearing carbonatite zone. It contains
mixed iron oxides and sulfides, along with a significant amount of
relict matrix carbonates. The iron oxides in this zone are derived
primarily from the variable partial to complete oxidation of
constituent sulfide minerals. The unoxidized sulfide-bearing
carbonatite at depth has not been leached of matrix carbonates and
retains all of its initial sulfide content.
Metallurgy of the oxide zone REE mineralization is well established and
described above. Initial metallurgical testing of the oxide-carbonate
zone resource indicates that mineral pre-concentration test results are
similar to those for the oxide zone mineralization. Bench-scale
testwork of the oxide-carbonate mineralization is continuing at both
MSRDI and Hazen Research. Preliminary results from the mineral
concentration testing are encouraging with recovery similar to the
oxide mineralization. The leach testwork results are expected within
the next few months.
The first set of test results indicate that rare-earth recoveries
ranging from 85 to 93 percent were achieved using the same leaching
criteria applied to the pre-concentrated high-grade and stockwork oxide
materials.
Table 3. Preliminary metallurgical results for the oxide-carbonate
material
|
Experiment | Residue Analysis, % | Extraction (solids basis), % |
Number | La | Ce | Pr | Nd | Eu | La | Ce | Pr | Nd | Eu |
Experiment 1
|
0.166
|
0.261
|
0.046
|
0.186
|
0.006
|
92
|
93
|
85
|
89
|
85
|
Experiment 2
|
0.144
|
0.239
|
0.038
|
0.167
|
0.006
|
93
|
93
|
88
|
90
|
85
|
Experiment 3
|
0.144
|
0.223
|
0.038
|
0.162
|
0.005
|
92
|
93
|
87
|
90
|
88
|
Experiment 4
|
0.167
|
0.256
|
0.042
|
0.185
|
0.006
|
91
|
93
|
86
|
89
|
85
|
Stockwork (lower grade) Testing
Bulk-tonnage, lower grade stockwork mineralization, averages
approximately 1 percent REO and occurs as an envelope around the
higher-grade oxide and oxide-carbonate zones. The stockwork zone is
extensive and only a small part of the potential has been tested by
drill holes. Scoping metallurgical testwork was completed for the lower
grade stockwork ore. Using the same upgrading and leaching parameters
as previously described, the REO content in the pre-concentrate was
approximately doubled, with a mass reduction of nearly 80 percent.
Subsequent hydrochloric acid leaching produced favorable rare-earth
extractions. Further metallurgical testing may allow the addition of
this material to the resource base.
Table 4. Mineral concentration by physical upgrading of stockwork
mineralization*
|
|
|
|
Sample | Weight | Assay | Distribution |
| % | % REO | % REO (Recovery) |
- 500 mesh
|
4.60
|
6.01
|
43.3
|
- 200 mesh
|
2.80
|
6.88
|
29.0
|
- 100 mesh
|
1.30
|
9.67
|
18.9
|
- 48 mesh
|
1.30
|
8.75
|
17.9
|
- ¼ inch
|
9.60
|
4.12
|
62.4
|
*using a head grade of approximately 2.4% REO
Heavy Rare Earths Testing Plans
West of the Bull Hill resource area, the Company discovered high grades
of heavy rare-earth elements in the Whitetail Ridge resource area, and
in the East Taylor and Carbon target areas. All three of the
mineralized zones are located in the western half of an expanding
rare-earth mineralized district (the Bear Lodge REE District).
Preliminary characterization of the western areas indicate high grades
(>3 percent REO) and substantial quantities of the light rare-earths,
along with some of the highest grades of heavy rare-earths in North
American REE deposits. They are particularly enriched in europium,
terbium, dysprosium, and gadolinium (Eu, Tb, Dy, and Gd). The East
Taylor and Carbon targets also contain significant yttrium.
Metallurgical samples are being collected and testing of the heavy
rare-earth mineralization will begin in the fourth quarter of 2011.
Rare Element Resources Ltd (TSX: RES & AMEX: REE) is a publicly traded mineral resource company focused on exploration and
development of rare-earth elements and gold on the Bear Lodge property.
Rare-earth elements are key components of the green energy technologies
and other high-technology applications. Some of the major applications
include hybrid automobiles, plug-in electric automobiles, advanced wind
turbines, computer hard drives, compact fluorescent lights, metal
alloys, additives in ceramics and glass, petroleum cracking catalysts,
and a number of critical military applications. China currently
produces more than 95 percent of the 130,000 metric tonnes of
rare-earths consumed annually worldwide, and China has been reducing
its exports of rare-earths each year. The rare-earth market is growing
rapidly, and is projected to accelerate if green technologies continue
to be implemented on a broad scale.
ON BEHALF OF MANAGEMENT
Jaye T. Pickarts, COO
Jaye T. Pickarts, P.E., serves the Board of Directors of the Company as
an internal, technically Qualified Person. Technical information in
this news release has been reviewed by Mr. Pickarts and has been
prepared in accordance with Canadian regulatory requirements that are
set out in National Instrument 43-101. This news release was prepared
by Company management, who take full responsibility for content.
Neither TSX nor its Regulation Services Provider (as that term is
defined in the policies of the TSX) accepts responsibility for the
adequacy or accuracy of this release.
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<p> For information, refer to the Company's website at <a href="http://www.rareelementresources.com">www.rareelementresources.com</a> or contact:<br/> Anne Hite, Director of Investor Relations (720) 278-2460 <a href="mailto:ahite@rareelementresources.com">ahite@rareelementresources.com</a><br/> Jaye T Pickarts, (720) 278-2460 <a href="mailto:jpickarts@rareelementresources.com">jpickarts@rareelementresources.com</a> </p>