Vermiculite

Vermiculite is a member of the phyllosilicate or sheet silicate group of minerals. It has the unique ability to expand to many times its original volume when heated - a property known as exfoliation. The majority of applications call for vermiculite in its exfoliated form.

Vermiculite has a wide range of uses that take advantage of its remarkable attributes of resilience to fire, refractory nature, thermal and acoustic insulation properties, absorption capacity, low density and ease of handling. Vermiculite is widely used in the construction industry, for horticultural applications, the automotive field, and for high temperature and industrial insulation uses.

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Vermiculite is a member of the phyllosilicate or sheet silicate group of minerals. It has the remarkable ability to expand to many times its original volume when heated - a property known as exfoliation. The term exfoliation is used to describe the heat expansion of the vermiculite, which occurs at right angles to the strong basal cleavage.

The name “vermiculite” is derived from the Latin vermicularis (worm-like) on account of the elongate, curved and twisted columns produced when the larger crystals are suddenly heated to high temperatures which releases the interlayer crystalline water.

Various chemical formulae are given for vermiculite. The general formula given below suggests a typical formula, which has been calculated from 65 vermiculite analyses. The basic structure of the mineral is identical to the micas and to talc: a 2:1 silicate sheet composed of two flat layers of silica and alumina tetrahedra (the tetrahedral layers), which are joined together in a layer composed of apical oxygen atoms, and magnesium, iron, and hydroxyl molecules (the octahedral layer). Between the 2:1 sheets lies the ion exchangeable layer. This layer will change in thickness depending on the interlayer cation present and the arrangement of waters of hydration associated with it.

The interlayer water is an essential component in the vermiculite. When a particle of vermiculite is rapidly heated, the interlayer crystalline water transforms into steam. The pressure of this steam evolution, forces the silicate layers apart from one another and the vermiculite flake forms an elongate concertina like particle twenty to thirty times its original thickness.

The majority of applications call for vermiculite in its exfoliated form. Vermiculite is a very versatile mineral. It is clean to handle, odourless and mould resistant. Vermiculite has a wide range of uses that take advantage of its remarkable properties: resilience to fire, refractory nature, thermal and acoustic insulation, absorption capacity, low density and ease of handling.

MAIN APPLICATIONS INCLUDE

  • Horticulture
  • Vermiculite plasters
  • Packing materials
  • Animal feedstuffs
  • Loosefill insulation
  • Bitumen coated vermiculite screeds
  • Silicate bonded shapes & blocks
  • Insulation in steelworks & foundries
  • Fire protection
  • Friction linings
  • Lightweight concretes
  • Refractory products