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Palabora Crude Vermiculite: Technical Data
Crude vermiculite from the Palabora mine consists of golden to brown flakes which are carefully classified into five grades - each with a specific range of particle sizes, as detailed in the table below:
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Grade
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Particle size distribution
mm 80% retained (mm)
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Loose Bulk density
kg/m3
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Loose Bulk densityLbs/ft3
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LARGE
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-8.0 + 2.8
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700 - 850
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43.7 - 53.1
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MEDIUM
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-4.0 + 1.4
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800 - 950
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49.9 - 59.3
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FINE
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-2.0 + 0.710
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850 - 1050
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53.1 - 65.6
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SUPERFINE
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-1.0 + 0.355
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850 - 1050
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53.1 - 65.6
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MICRON
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-0.710 + 0.250
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850 - 1050
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53.1 - 65.6
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* With compaction in storage or transit this can increase to 1250 kg/m3 / 78.0 lb/ft3
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Chemical Analysis:
The chemical analysis of both the crude and exfoliated vermiculite are effectively the same.
Typical Ranges for Major Components:
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SiO2
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39 - 42%
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Al2O3
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8.5 - 10.0%
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Fe2O3
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8.0 - 9.5%
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MgO
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22 - 24.5%
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K2O
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5.0 - 6.5%
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Angle of Repose:
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38o to 26o according to grade
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Specific Heat:
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1.03 kJ/kg.K. at 20oC1.05 kJ/kg.K. at 30oC
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Specific Gravity:
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2.5 to 2.6 depending on grade
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Mohs Hardness:
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Between 1 & 2
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pH Value:
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8.0 to 9.0
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Weight Loss:
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at 105oC - 4.5 to 6.5%at 850oC - 8.0 to 10.0%
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Aspect Ratio:
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As received, this varies from 7:1 to 30:1 depending on grade. Mechanical processing can produce aspect ratios of 50:1.Chemical and mechanical processing can produce ratios of 200:1.
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Cation Exchange:
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The principle exchangeable cation normally present in vermiculite is magnesium (Mg). The cation exchange capacity of Palabora vermiculite is up to 600 milliequivalents per kg. The rate of cation exchange will depend on exposed surface area; therefore, the best results are obtained using exfoliated vermiculite.
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