What is Vermiculite?
Vermiculite is a hydrated magnesium aluminum sheet silicate mineral closely related to mica, and has all of the thermal and chemical resistance mica is known for.
When subjected to heat, vermiculite expands and forms particles that are revered for being:
- Lightweight
- Incombustible
- Compressible
- Highly absorbent, soaking up to three times its volume in water
- Non-reactive
- Highly effective in cation exchange capacity
It’s colour can vary slightly according to it’s origin, from greyish to brown
Vermiculite is mined using open cast mining techniques in many countries across the globe including South Africa, China and Brazil.
It is then classified into grades and shipped to the processing plants where rock and other impurities are removed.
The ore granules are then exfoliated using a high temperature furnace before being processed further towards the intended application.
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Element (Percent by Weight)
- SiO2 38 to 46
- AL2O3 10 to 16
- MgO 16 to 35
- CaO 1 to 5
- K2O 1 to 6
- Fe2O3 6 to 13
- TiO2 1 to 3
- H2O 8 to 16
- Other 0.2 to 1.2
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- Colour Light to dark brown
- Shape Accordion-shaped granule
- Bulk densitya 64 -160 kg/m3, 4-10 lb/ft3
- Moisture loss at 110C(230F) 4 to 10%
- pH (in water) 6 to 9
- Combustibility Non-combustible
- Sintering temperature 1150 - 1250C, 2100 - 2280F
- Fusion point 1200 - 1320C, 2200 - 2400F
- Cation exchange capacity (*b) 50 - 100 me/100g
- Specific heat: 0.84 - 1.08 kJ/kgK 0.20 - 0.26 kcal/kgK 0.20 - 0.26 Btu/lb F
- Waterholding 220 - 325% by weight capacity (*a) 20 - 50% by volume
Notes: a > Bulk density and water holding capacity vary with particle size. b > Exchangeable ions are Mg+2 and Ca+2 sodium acetate saturation / ammonium acetate substitution method
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Bulk Density Thermal Conductivity
kg/m3 (lb/ft3) W/mK (Btu in/ft2h F)
56-64(3.5-4) 0.058(0.40)
80-96(5-6) 0.064(0.44)
160-192(10-12) 0.071(0.49)