Palabora Vermiculite is a lamellar flake-like hydrated magnesium-iron-aluminium silicate. Geologically Palabora vermiculite arises from the weathering, over time, of phlogopite mica. During the weathering process alkalis present in the mica are leached and replaced with water.
When subjected to high temperatures, this inter-lamellar water is converted to steam, driving the vermiculite flake apart at right angles to the lamellar plane. Commercially this process is known as exfoliation. This results in an expanded low density aggregate with a diverse range of end uses.
Bisley & Company have nearly 30 years experience in the vermiculite business. Currently Bisley supplies unexpanded Palabora vermiculite ore to the Australian, New Zealand and Middle East markets. Palabora, a subsidiary of the giant Rio Tinto Group, is the world's largest producer of vermiculite with capacity in excess of 200,000MT p.a.
The Palabora vermiculite mine is located in the Northern Province of South Africa. Feed from this ore body is carefully dried and beneficiated in a complex multi-stage process to produce five vermiculite grades, characterised as follows:
Sizing (80% retained)
Micron -0.71 +0.25mm
Superfine -1.0 + 0.355mm
Fine -2.0 +0.71mm
Medium -4.0 +1.4mm
Large -8.0 +2.8mm
The scale of operations at Palabora, coupled with attention to detail in geological sampling, mining and product processing under ISO9002 and ISO 14001 quality assurance and environmental regimes, guarantee a consistent product which has become regarded as the industry standard worldwide. Each and every vermiculite shipment supplied by Bisley is backed by comprehensive Analysis Certificates linked to customer order numbers.
Most vermiculite is used in its exfoliated form. Exfoliated vermiculite possesses anumber of useful attributes. Aside from its very low density, it has low thermal conductivity, is non-combustible, odorless, thermally stable, sterile and insoluble in water. Following are some of the more important applications for vermiculite in this form.
Palabora Vermiculite, typically combined with peat and sometimes other media, is widely used as a component of potting mixes for plant propagation. In this capacity vermiculite aids aeration and water retention. In addition, its cation exchange capacity promotes the controlled release of added fertilisers. Collectively these attributes are highly conducive to plant growth.
Palabora Vermiculite has a proven propagation track record across a diversity of plant species in Australia and New Zealand, and indeed worldwide.
Palabora Vermiculite may be combined with Cement or Plaster and other materials to manufacture spray-applied fire resistant coatings for use on structural steel. Vermiculite based premixes of this type offer excellent fire resistance, good coverage, enhanced adhesion to the substrate and reduced thermal conductivity.
Palabora Vermiculite is often used as a lightweight insulating aggregate in refractory castables and moulded refractory shapes. When mixed with silicates and other binders, Palabora vermiculite is used to manufacture insulating boards for use in the aluminium industry and other refractory applications.
Vermiculite is now used extensively in the friction lining industry as a safe alternative to asbestos.
Plasterboard / Drywall / Gypsum-board
In addition to the above there are a number of applications of vermiculite in its crude, un-exfoliated state. Perhaps the most significant of these is the utilisation of vermiculite ore in manufacture of fire-resistant plasterboard. When exposed to fire, vermiculite particles incorporated in the plaster mix expand, counteracting the natural tendency for plaster to shrink on exposure to heat.
The result is plasterboard which remains dimensionally stable under aggressive fire conditions.