Vermiculite is a mineral, a hydrated magnesium aluminosilicate, with a highly variable and complex chemical composition. It crystallizes in the monoclinic crystal system, most commonly in the form of platy aggregates, crystals, or flakes. It has a golden-beige color. It is the result of the weathering of micas (phlogopite, i.e., brown mica, or biotite, i.e., black mica). It contains compounds of magnesium, iron, aluminum, oxygen, and hydrogen. It is mined mainly in the USA, Africa, Australia, and Asia. In Poland, it occurs in Lower Silesia, but these are non-commercial quantities not suitable for exploitation.
A characteristic feature of vermiculite is its ability to expand up to 20 times in volume during high-temperature processing. This process produces expanded vermiculite, which has the form of swollen concertina-like particles. Vermiculite in exfoliated (expanded) form is lightweight, non-combustible, compressible, highly absorbent, provides excellent sound and thermal insulation, is chemically unreactive, and has an exceptional capacity to store and release moisture. It is also completely safe for both humans and the environment. A very wide operating temperature range (from -260 to 1200 °C) makes it suitable for a vast number of applications.
| VERMICULITE | ||||
| SUPERFINE | FINE | MEDIUM | LARGE | |
| grain size | % | % | % | % |
| 4 mm | 8-50 | 55-95 | ||
| 2 mm | 0-1 | 20-35 | 20-45 | 3-20 |
| 1.6 mm | 0-2 | 18-30 | 5-20 | 1-10 |
| 1 mm | 8-40 | 20-40 | 5-20 | 1-10 |
| 0.5 mm | 10-55 | 5-15 | 5-15 | 0-8 |
| 0.25 mm | 10-30 | 2-10 | 1-5 | 0-3 |
| Bulk density | 110-120 kg/m3 |
80-100 kg/m3 |
60-110 kg/m3 |
70-110 kg/m3 |
| Moisture content | max 5% | max 5% | max 5% | max 5% |
| PHYSICAL PROPERTIES | |
| form | solid state in the form of granules with a lamellar structure and a grain size of 0-8 mm |
| odor | odorless |
| pH | 6.5-7.5 |
| flammability | non-flammable, class A1 |
| relative density | bulk density 60-200 kg/m3 |
| melting point / range | above 1300oC |
| auto-ignition temperature | not applicable |
| thermal conductivity | 0.050-0.065 W/m x K |
| water absorption | up to 150% |
| compressive strength | 0.14-0.40 MPa |
| chemical resistance | similar to glass |
| acoustic absorption | 10-92% |
| specific heat | 0.84-1.08 kJ/kgoC |
| CHEMICAL PROPERTIES |
|
| Chemical Composition | Percentage % |
| SiO2 | 38-46% |
| Al2O3 | 10-16% |
| MgO | 16-35% |
| Fe2O3 | 6-13% |
| TiO2 | 1-3% |
| CaO | 1-5% |
| K2O | 1-6% |
| H2O | 8-16% |
| other | 0.2-1.2% |
APPLICATIONS (click on an application of interest)
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