Mica
Mineralogy
Mica is a naturally occurring, highly lamellar phyllosilicate of aluminium
and potassium that exhibits an almost perfect basal cleavage.
This means that mica particles
can be easily split into thin, often transparent sheets.
Amongst platy minerals, micas are unique due to the broad range of particle sizes naturally available, from microns up to several centimetres. Mica is often referred to as ‘glimmer’, a description of the visual effect that it imparts.
Imerys mica powders are extracted from deposits along with kaolin and feldspar. They are distinguished from other silicate minerals mainly by their high aspect ratio and elasticity. Using a variety of selection and processing methods mica is separated from the other minerals, creating materials with a range of particle sizes.
Mica is widely distributed and occurs in igneous, metamorphic and sedimentary rocks. Large crystals of mica used for various applications are typically mined from granitic pegmatites.
Physical properties
Chemical resistance- Thermal conductivity (anisotropic)
- Heat stability, passive fire retardancy
- Vibration damping
- Low coefficient of friction (lubricants, extrusion)
- Hydrophilic
- Flexible
Applications
The particle shape and chemical composition of mica allows it to be used to increase chemical, corrosion, cracking, weather and UV-resistance in paints and varnishes. When formulated into paint and mortar, mica can give a very smooth finish and easy dispersion. Coarser grades are used to give a decorative, pearlescent effect.
Mica is widely used to improve the acoustic qualities of sound insulation, in automotive applications for example.
The strength and elastic properties of mica are harnessed in the plastic industry for the production of complex injection moulded parts.
In fiber cement construction panels mica improves fire resistance by reducing panel shrinkage and is ideal for use in wet room fiberboard. Imerys mica is also used as a fire-resistant material in cementitious spray mortars where it provides heat shielding to steel beams, extending building exit time during fires.
