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File:PerliteUSGOV.jpg

Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral and a commercial product useful for its light weight after processing.

PropertiesEdit

File:Perlite-nps-02316.jpg

When it reaches temperatures of 850–900 °C (1560-1650 °F), perlite softens (because it is a glass). Water trapped in the structure of the material vaporises 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") perlite has a bulk density around 1100 kg/m3 (1.1 g/cm3), while typical expanded perlite has a bulk density of about 30–150 kg/m3 (0.03-0.150 g/cm3). Template:-

Production and usesEdit

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Perlite is a non-renewable resource. The world reserves of perlite are estimated at 700 million tonnes. In 2011, 1.7 million tonnes had been produced, mostly by Greece (500,000 t), United States (375,000 t) and Turkey (220,000 t). However, no information for China – a leading producer – was available.[1]

Because of its low density and relatively low price (about US$50 per tonne of unexpanded perlite), many commercial applications for perlite have developed. In the construction and manufacturing fields, it is used in lightweight plasters and mortars, insulation and ceiling tiles.[2]

In horticulture, perlite can be used as a soil amendment or alone as a medium for hydroponics or for starting cuttings. When used as an amendment it has high permeability / low water retention and helps prevent soil compaction.

Perlite is an excellent filter aid. It is used extensively as an alternative to diatomaceous earth. The popularity of perlite usage in this application is growing considerably worldwide. Perlite filters are fairly commonplace in filtering beer before it is bottled.

Small quantities of perlite are also used in foundries, cryogenic insulation, as a lightweight aggregate in mortar (firestop) and in ceramics as a clay additive. It is also used by the explosives industry.[3]

In 2010, estimated perlite consumption in the US was as shown in the table:[1]

Fraction use[2]
53% building construction products
14% horticultural aggregate
14% fillers
8% filter aid
11% other

The cost of unexpanded perlite has varied since 2001.:[4]

end of
year
Price in the US
$ per t
2001 36.3
2002 36.5
2003 38.2
2004 41.8[2]
2005 40.5[2]
2006 42.9
2007 45.3
2008 48.0
2009 49.0

Typical analysis of perliteEdit

See alsoEdit

  • Expanded clay aggregate, an alternative lightweight filler for building materials
  • Biochar, the large surface area of carbon molecules increases the soil structure, aeration, nutrient and water retention capacity. Biochar creates a healthy soil in which micro-organisms thrive
  • Vermiculite, many expanders of perlite are also exfoliating vermiculite and belong to both trade associations
  • Diatomite, used for filter-aids
  • Industrial minerals
  • Mortar (firestop)

ReferencesEdit

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External linksEdit

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