Crude Vermiculite from the mine consists of golden to brown flakes which are carefully classified into five grades – each with a specified range of particle sizes, as detailed in the table below:
| Grade | Particle size distributionmin. 80% retained (mm) | Loose bulkDensity kg/m3 |
|---|---|---|
| LARGE | -8.0 + 2.8 | 700 – 850 |
| MEDIUM | -4.0 + 1.4 | 800 – 950 |
| FINE | -2.0 + 0.710 | 850 – 1050 |
| SUPERFINE | -1.0 + 0.355 | 850 – 1050 |
| MICRON | -0.710 + 0.250 | 850 – 1050 |
| * The above specified values may vary to the actual values | ||
Exfoliated Vermiculite
Vermiculite is most widely used in its exfoliated form. The concertina-shaped granules of exfoliated vermiculite are non-combustible as well as being insoluble in water and all organic solvents. Safe and easy to handle, exfoliated vermiculite is available in the market place in five different grades as shown in the table below:
Volume Yields For Exfotliated Vermiculite
| Grade | Typical loose bulkdensities of product (kg/m3) | per ton of crudevermiculite processed (m3) |
|---|---|---|
| MICRON | 105 – 135 | 7.5 – 9.0 |
| SUPERFINE | 85 – 100 | 8.5 – 10.0 |
| FINE | 75 – 85 | 10.5 – 11.5 |
| MEDIUM | 70 – 85 | 11.5 – 13.0 |
| LARGE | 60 – 75 | 13.0 – 14.5 |
| * The above specified values may vary to the actual values | ||
The above values are those obtained by commercial operation and these values may vary for different designs of exfoliate.
| pH Value | – | 7.5 – 9.0 |
| Thermal Conductivity | – | 0.063 – 0.069 W/mºC under ambient |
| Specific Surface Area | – | The specific surface area for exfoliated vermiculite, as measured by the nitrogen absorption technique, is typically: |
| Specific SurfaceArea | m2/g |
|---|---|
| MICRON | 6.4 |
| SUPERFINE | 5.4 |
| FINE | 4.4 |
| MEDIUM | 4.0 |
Chemical Analysis
The chemical analysis ofp both crude and exfoliated vermiculite is the same
| Typical Ranges for Major Components | |
|---|---|
| SiO2 | 35 – 46% |
| Al2O3 | 6.0 – 10.0% |
| Fe2O3 | 6.0 – 9.5% |
| MgO | 21.5 – 25.5% |
| K2O | 3.0 – 6.0% |
| Typical Ranges for Minor Components | |
|---|---|
| CaO | 2.0 – 6.0% |
| CO2 | 0.6 – 2.5% |
| TiO2 | 0.6 – 1.4% |
| F | 0.2 – 0.8% |
| Cr2O3 | 0.01 – 0.10% |
| P | 0.2 – 2.0% |
| Cl | 0 – 0.5% |
| Angle of Repose | – | 38º to 26º according to grade |
| Specific Heat | – | 1.03 kJ.K. at 20ºC 1.05kJ/kg.K. at 30ºC |
| Specific Gravity | – | 2.5 to 2.6 depending on the grade |
| Mohs Hardness | – | Between 1 & 2 |
| pH Value | – | 8.5 to 10 |
| Weight Loss | – | At 105ºC – 4.5 to 6.5%. At 95ºC – 8.0 – 10.0% |
