Preliminary metallurgical test work - Ngualla Rare Earth
Exploration Update | Drilling Report
31-01-2012
EARLY ENCOURAGEMENT FROM
PRELIMINARY METALLURGICAL TEST
WORK – NGUALLA RARE EARTH PROJECT
Highlights:
• Non – optimised initial acid leach test work on a composite sample of weathered mineralisation
leaches 88% of rare earths.
• Further leach test work has been prioritised to evaluate the possibility of a relatively simple processing
route to produce a high grade rare earth concentrate for this higher grade, near surface portion of
the Ngualla rare earth mineralisation.
• Simple wet table characterisation of primary fresh rock rare earth mineralisation produces positive
beneficiation results in preliminary sighter tests.
Background
Ngualla in southern Tanzania is one of the largest and better grade new rare earth discoveries of recent years.
The Company is on track to complete the maiden JORC compliant rare earth resource estimate for the Southern
Rare Earth and South West Alluvial Zones before the end of the March 2012 quarter.
Rare earth mineralisation within the Southern Rare Earth Zone at Ngualla occurs from surface in the following main hosts:
1. iron rich gravel colluvium and ferricrete. Typical grade 1 to 4 % REO*
2. highly weathered carbonatite, rare earth enriched, iron and barite rich, the original carbonate minerals are completely
leached – typically 2.5 to 7% REO
3. fresh, primary carbonatite rock, iron poor, carbonate rich – 1.5 to 2.5% REO
*REO = Total Rare Earth Oxide
Mineralogical studies have shown that bastnasite and synchysite are the main rare earth minerals and occur within a barite –
iron oxide hydroxide lithology in the weathered zone and a carbonate rich lithology with barite in fresh carbonatite. Alumina is
negligible and there are no clay minerals. Uranium and thorium levels are very low at 17ppm and 37ppm average respectively
within +1% REO mineralisation in the Southern Rare Earth Zone. The rare earth carbonates are predominantly liberated, with
grain sizes between 10 and 120 microns.
Mineralisation in the South West Alluvial Zone (Figure 1) occurs from surface over a wide area within unconsolidated
(potentially ‘free-dig’) material at grades of 2 to 4% REO. Rare earth mineralisation in the Northern Niobium – Tantalum –
Phosphate Zone ranges in grade from 1 to 2.5% REO but is also accompanied by niobium mineralisation in the 0.25 to 1.5%
Nb2O5 range and phosphate at 15 to 25% within an iron rich magnetite – apatite rock.
These rock types have different chemical and physical
properties, leading to the potential for different opportunities
regarding beneficiation and concentrate production routes
for each.
Metallurgy, including beneficiation, is a key driver for
development time, capital and operating costs for rare
earth projects and the Company has implemented a
large test work program to address these issues. Peak’s
appointed metallurgical consultants Bateman Engineering
are overseeing a series of studies on bulk diamond core or
RC drill chip samples of each of the styles of mineralisation,
which were obtained from the recently completed drilling
program. Individual tests (Figure 2) include crushing,
grinding, screening, heavy liquid separation, wet table, magnetic separation, flotation and direct acid leach to determine the
optimal method to produce a rare earth concentrate (and / or niobium – tantalum or phosphate for the Northern Zone sample).
Initial positive results from some early baseline studies have already been received and are presented below.
Leach test work – weathered mineralisation
Preliminary acid leach test work on eight reverse circulation (RC) drill samples of weathered rare earth mineralisation from the
Southern Rare Earth Zone has produced some early encouragement with between 8 and 92% of rare earths leached.
Eight samples were tested, seven being individual two metre composite samples from single RC drill holes. The remaining
sample was a bulk composite of 25 x 2m composite samples from six RC holes. The tests used 11% sulphuric acid at
atmospheric pressure and a temperature of 900 centigrade for a total period of 22 hours.
Of the eight samples tested, one sample showed very low (8%) rare earth leach extraction. Two samples leached 30% and 46%
of the rare earths. The remaining five samples showed encouragingly high rare earth leach extractions of 65%, 87% 88%, 88%
and 92% (Table 1). Importantly, the more representative bulk composite sample showed an 88% rare earth leach extraction.
Acid consumption rates varied from 83 to 366kg/tonne (see Table 1).
These are first pass, basic sighter test results on a small number of samples. Test work has not yet been optimised to reduce
acid consumption and increase rare earth recovery, and further work will be completed with the aim of improving on these
initial results. Additional work is planned to determine the cause of the wide variation in rare earth leach extraction and acid
consumption, so that these may be improved and / or preferential parts of the deposit identified for potential processing by
acid leach.
Test work is also proceeding to determine what grade of rare earth concentrate may be achievable by the sequential precipitation
of the rare earth solution.
The Company considers these initial leach results to be encouraging and has prioritised further test work to evaluate the
possibility of a relatively simple processing route that will produce a high grade rare earth concentrate for this higher grade,
near surface portion of the Ngualla rare earth mineralisation.
Beneficiation of primary mineralisation
Initial beneficiation studies on a bulk diamond core sample of fresh rock rare earth mineralisation from the Southern Rare Earth
Zone returned encouraging upgrades of mineralisation from wet table test work. This initial basic baseline test work succeeded
in concentrating 84% of the head feed mineralisation, with a grade of 1.69% REO, 290% (almost 3 x’s) to 4.87% REO. The
concentrate is contained within just 34% of the mass of the original feed material (an alternative presentation of these initial
results is that 66% of the original mass is able to be discarded for the loss of just 16% of the mineralisation).
Although this single stage preliminary beneficiation characterisation work has not immediately produced a commercial grade
concentrate, it has demonstrated the potential for simple gravity separation to form an important component of a multi – part
processing stream for this important second style of rare earth mineralisation at Ngualla.
Similar to the leach test work, these are first pass, basic sighter test results on a single sample of primary, fresh rock
mineralisation. Test work has not yet been optimised for grain size or other factors and further work will be completed with
the aim of improving on these initial results. Further test work on these and other beneficiation techniques and combinations
thereof are required and are currently in progress to identify an optimal processing route that will produce a commercial grade
rare earth concentrate product from this fresh rock mineralisation.
The Company considers these initial beneficiation results to be encouraging and will continue to provide updates on results of
the various beneficiation and metallurgical test work programs as they come to hand.
Richard Beazley Managing Director
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