MINERALOGICAL ANALYSIS FOR THE CHURCHILL RIVER MINERAL SANDS PROJECT
Mineral sand deposits such as Churchill river produce and sell mineral concentrates of the different mineral present. The prices of these minerals are set by global negotiation between producers and consumers. In order to design an extraction plant and determine the quality of concentrates to be sold extensive mineralogical tests are necessary.
Of immediate interest are the potential qualities of the different magnetic fractions for iron and titanium content, as it relates to marketability of products. Mineral analyses included:
• Microscopic Examination (Point Count Analysis),
• Electron microprobe analysis,
• XRF assaying and
• QEMSCAN Analysis.
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Microscopic Examination
Firstly, mineral point counts were done on 4 raw samples and included over 2200 grains. The sand fraction in the size range from 0.0625 to 1.5 mm. Point count analysis of concentrate indicated high percentage of iron bearing magnetites (average 44.16%), titanium bearing ilmenites (average 28.48%), and garnets (average 12.89%).
Secondly, microscopic examination was done on four heavy concentrate samples. A simple first look of microscopic examination involves using transmitted light to identify the potential valuable iron and titanium mineral grains, which are opaque, from silica and silicate mineral grains, which are translucent to transparent, and include potentially valuable zircon and garnet grains. Magnetite, titaniferous magnetite or titanomagnetite, and ilmenite, are all opaque and are black in reflected light.
|
|
500 gauss* transmitted light. Approx 40x.Approx. 90% black, opaque, magnetite grains |
Non-Mag (5000 gauss*) transmitted light. Approx. 40x. Approx. 50% silica, with tourmaline, kyanite, some zircon and possible rutile. |
 |
 |
500 gauss reflected light. Approx 40x. |
Non-Mag (5000 gauss) reflected light. Approx 40x |
 |
 |
5000 gauss transmitted and reflected light. Approx. 100x. |
Non-Mag (5000 gauss) transmitted and reflected light. Approx. 100x. Rounded shiny zircon grain at right center |
|
*Gauss= A unit of magnetic induction, equal to 1 Maxwell per square centimeter. |
Point counts were conducted on each of the magnetic fractions from sample 25A
| 500 gauss magnetic |
| Mineral |
# of grains |
% |
| Magnetite |
227 |
91.5 |
| Silica |
21 |
8.5 |
|
| Total |
248 |
100.0 |
| 2500 gauss magnetic |
| Mineral |
# of grains |
% |
| Ilmenite |
182 |
70 |
| Silica |
37 |
14.2 |
| Pyroxene and Amphibole |
41 |
12.8 |
|
| Total |
260 |
100.0 |
| 5000 gauss magnetic |
| Mineral |
# of grains |
% |
| Ilmenite |
34 |
1.3 |
| Garnet |
48 |
18.4 |
| Pyroxene and Amphibole |
57 |
21.8 |
| Tourmaline |
23 |
8.8 |
| Hematite |
63 |
24.1 |
| Silica |
36> |
25.6 |
|
| Total |
261 |
100.0 |
| 5000 gauss Non-magnetic |
| Mineral |
# of grains |
% |
| Rutile |
15 |
5.1 |
| Pyroxene and Amphibole |
41 |
13.9 |
| Tourmaline |
26 |
8.8 |
| Zircon |
27 |
9.2 |
| Silica |
186 |
63.0 |
|
| Total |
295 |
100.0 |
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Conclusions
An estimated 15% percent of the heavy mineral suite contains magnetite with 2% or less TiO2 content. Another 40 to 50 percent contains varying concentrations of iron and titanium, in the form of titaniniferous magnetite, ilmenite, and possibly a small amount altered ilmenite/leucoxene and rutile.
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Electron microprobe analysis
Microprobe test showed the welcome absence of chromium, vanadium, and calcium with negligible magnesium, all ideal for sale to the iron and pigment industry.
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Quantitative XRF assaying
In 2004 quantitative XRF assaying was done on 10 heavy mineral concentrate samples for evaluation for iron, titanium mineral potential.
Each of the ten heavy mineral samples were weighed and assayed for TiO2and Fe2O3 content with a an energy dispersive Spectro-Asoma 200T XRF unit. Results indicate that TiO2 and Fe2O3 content in the ten samples is consistent.
Initial magnetic fractionation of each sample was conducted with a series of different intensities of hand lift magnets, chosen to separate know standards of magnetic susceptibilities. This gives a good indication of magnetic mineral distributions.
Magnetic Fractionation Analyses |
|
500 gauss |
2500 gauss |
Sample |
TiO2% |
Fe2O3% |
Wt grams |
TiO2% |
Fe2O3% |
Wt grams |
3A |
2.5 |
88 |
3 |
8.2 |
75 |
8 |
4C |
1.2 |
87.7 |
2 |
7.8 |
72.1 |
9 |
5B |
2.2 |
87.7 |
2 |
8.2 |
72.4 |
8 |
7B |
1.8 |
84.2 |
2 |
7.4 |
70.4 |
10 |
6A |
2.2 |
78.2 |
2 |
5.9 |
64.1 |
6 |
20C |
1.4 |
88.3 |
2 |
7.1 |
72.2 |
9 |
21A |
1.5 |
89.2 |
2 |
7.7 |
71 |
6 |
23A |
0.6 |
89.9 |
2 |
7.8 |
68.7 |
9 |
24A |
1 |
88.7 |
2 |
7.6 |
69.7 |
10 |
25A |
0.1 |
90.6 |
2 |
8.1 |
73.2 |
5 |
|
Average |
1.45 |
87.25 |
|
7.58 |
70.88 |
|
Av Wt% |
|
|
10.5 |
|
|
40 |
The analysis showed that a true magnetite fraction is present in the 500 gauss magnetic range, with an average content of approximately 87%
Fe2O3 and, 1.5% TiO2. This averages approximately 10 weight percent of the heavy mineral content, which is in agreement with heavy liquid separation studies done at Dallhousie University at Halifax.
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QEMSCAN Analysis
QEM SEM analysis provides a grain by grain determination of total elemental content, including impurities within grain inclusions. This is very valuable in metallurgical work, and the aim of the analysis was to characterize the bulk mineralogy of the sample including minor and trace phases, with particular interest in the purity of Fe(Ti) oxides and zircon phases.
The QEMSCAN mode of measurement used to measure these samples was Particle Mineral Analysis (PMA), which generates
• particle images
• quantifies the modal mineralogy of the sample
• provides an estimate of the grain size of the various species identified
• and produces information on a particle-by-particle basis.
Over 2000 particles were measured for each sample
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QEMSCAN Results
Mineral Groupings
During automated analysis, QEMSCAN data are collected using a very detailed chemical-based mineral list. The following mineral grouping was applied to the Churchill mineral sands analysis.
• Rutile – Pure TiO2.
• Leucoxene – Includes Fe Ti oxides with low levels of Fe.
• Ilmenite – Includes Fe Ti oxides with medium levels of Fe.
• Ti-Magnetite – Includes low Ti-bearing Fe oxides.
• Fe Oxides – Includes all Fe oxides phases.
• Ti Al Oxides – Includes Ti oxides with low levels of Al.
• Zircon – Includes zircon minerals.
• Al Silicates– Includes all Al silicate phases.
• Al (Fe, Mg ,K) Silicates– Includes Al Fe, Al Fe Mg, Al Fe K, Al Fe Mg K silicate phases.
• Al Ca Silicates – Includes all Al silicate phases containing Ca.
• Ca Silicates – Includes Ca Mg and Ca Fe Mg silicate phases.
• Fe Silicates – Includes Fe, Fe Mg and Fe K silicate phases.
• Other Silicates– Includes all other silicate phases as well as Ti silicate phases.
• Quartz – Pure SiO2.
• Hercynite – Fe Al oxide.
• Other – All other phases not included above occurring in trace form such as Chromite, Monazite, Apatite and Corundum.
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QEMSCAN Assay and Modal Results
The QEMSCAN calculated modal analyses and the chemical assay for the samples submitted are provided in Tables 1 and 2 below. The QEMSCAN modal results are presented in terms of weight percent for each of the mineral groupings, and the chemical assay is presented in terms of weight percent.
Table 1 QEMSCAN Modal Summary |
| Mineral |
Sample 25A |
Sample 5B |
Sample 4C |
Rutile |
0.1 |
0.1 |
0.3 |
Leucoxene |
0.1 |
0.1 |
0.1 |
Ilmenite |
4.1 |
4.3 |
3.4 |
Ti Magnetite |
31.4 |
30.8 |
24.2 |
Fe Oxides |
13.3 |
9.0 |
9.0 |
Ti Al Oxides |
2.0 |
1.6 |
2.3 |
Zircon* |
0.4 |
0.1 |
0.3 |
Al Silicates |
5.5 |
5.7 |
7.5 |
Al (Fe,Mg,K) Silicates |
7.6 |
7.4 |
7.4 |
Al Ca Silicates |
18.9 |
24.3 |
25.6 |
Ca Silicates |
4.6 |
4.7 |
6.2 |
Fe Silicates |
4.9 |
5.4 |
6.0 |
Other Silicates |
2.1 |
1.8 |
2.1 |
Quartz |
1.2 |
1.7 |
1.9 |
Hercynite |
1.8 |
1.8 |
2.1 |
Other |
1.8 |
1.3 |
1.6 |
|
Total |
100.00 |
100.00 |
100.00 |
| *Recent studies indicate >1% zircon |
|
|
The modal summary shows all samples high in Ti-Magnetite, Fe oxides and silicate phases.
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Textural Indications
Particle maps are produced as a part of the QEMSCAN PMA mode of analysis, and are a useful tool in visualizing the textural relationships that occur between mineral phases.
The color legend depicted here is applicable to Figure 1.
|
Figure 1 QEMSCAN mineral map of representative particles from Sample 25A Particles are sorted in order of decreasing size. Total population = 2607 particles. |
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Particle Population Distribution
Figure 2 shows the distribution of particle types. These categories define a population of particles rather than the elemental composition of individual particles.
Figure 2 Distribution of particles within above defined categories, presented in the grid.
|
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Zircon
Less than 0.5% zircon was identified in all samples using QEMSCAN analysis. However more recent XRF analysis suggest zircon content between 1-2%. Figure 3 shows the zircon particles present for the three samples.
• Sample 25A contains 58 Zr-bearing particles, of which 11 are liberated particles containing >65% ZrO2 with fine inclusions of Fe oxides, Ti magnetite and silicates.
• Sample 5B contains 52 Zr-bearing particles, of which 8 are liberated particles containing >64% ZrO2 with fine inclusions of silicates.
• Sample 4C contains 43 Zr-bearing particles, of which 9 are liberated particles containing >63% ZrO2 with fine inclusions of Fe oxides, Ti magnetite and hercynite.
Figure 3 Liberated Zr-bearing particles for samples 25A, 5B and 4C. |
Sample 25A
|
Sample 5B |
Sample 4C |
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