- Perlite
Perlite is an
amorphous volcanic glass that has a relatively highwater content, typically formed by the hydration ofobsidian . It occurs naturally and has the unusual property of greatly expanding when heated sufficiently.Properties and uses
When it reaches temperatures of 850–900 °C, perlite softens (since it is a glass). Water trapped in the structure of the material vapourises and escapes and this causes the expansion of the material to 7–16 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles.
Unexpanded ("raw") perlitebulk density : around 1100 kg/m³ (1.1 g/cm³).
Typical expanded perlite bulk density: 30–150 kg/m³Due to its low density and relatively low price, many commercial applications for perlite have developed. In the
construction and manufacturing fields, it is used in lightweightplaster s and mortars, insulation, ceiling tiles and filter aids. Inhorticulture it makes composts more open to air, while still having good water-retention properties; it makes a good medium forhydroponics . Perlite is also used in foundries,cryogenic insulations, as a lightweight aggregate inmortar (firestop) and in ceramics as aclay additive.Typical analysis of perlite
*70-75%
silicon dioxide : SiO2
*12-15%aluminium oxide : Al2O3
*3-4%sodium oxide : Na2O
*3-5%potassium oxide : K2O
*0.5-2%iron oxide : Fe2O3
*0.2-0.7%magnesium oxide : MgO
*0.5-1.5%calcium oxide : CaO
*3-5% loss on ignition (chemical / combined water)Production trends
In 2005, Greece was the top producer of perlite with at least one-third world share followed by China, USA, Japan and Turkey [Reported by the
British Geological Survey ] .In
2001 the cost of perlite was about US$36.31 permetric ton . The yearend price for mined perlite in the US has increased since then [cite journal
author =
year = 2006
month = January
title = Perlite
journal = U.S. Geological Survey Mineral Commodity Summaries,
volume =
issue =
pages = 122–123
id = [http://minerals.usgs.gov/minerals/pubs/commodity/perlite/perlimcs06.pdf] ] ::2001.....$36.3 permetric ton :2002.....$36.5 per metric ton:2003.....$38.2 per metric ton:2004.....$40.6 per metric ton:2005.....$42.5 per metric tonee also
*
Vermiculite (Many expanders of perlite are also exfoliating vermiculite and belong to both trade associations)
*Diatomite (used for filter-aids)
*Industrial minerals
*Mortar (firestop) References
External links
* [http://www.perlite.org The Perlite Institute]
* [http://www.perlite.info Perlite Information Source]
* [http://www.incon-corp.com Manufacturer of Perlite Expansion Equipment]
* [http://www.mii.org/Minerals/photoperlite.html Mineral Information Institute - perlite]
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