Difference between revisions of "Perlite"
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Latest revision as of 09:14, 20 September 2010
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.
Contents
Properties
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") 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.
Uses
Due 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 lightweight plasters and mortars, insulation, ceiling tiles, in horticulture and as filter aid.
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 helps prevent water loss and 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.
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 explosive industry.[1]
In 2007, estimated U.S. usage applications are shown in the following table:
| portion | general usage[2] |
|---|---|
| 60% | building construction products |
| 14% | horticultural aggregate |
| 11% | fillers |
| 7.5% | filter aid |
| 7.5% | other |
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.[3]
The cost of 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 | 51.6 |
| 2008 | 60.0 |
See 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
- ↑ Emulsion explosive composition containing expanded perlite United States Patent 4940497
- ↑ 2.0 2.1 2.2 http://minerals.usgs.gov/minerals/pubs/commodity/perlite/mcs-2008-perli.pdf
- ↑ Reported by the British Geological Survey
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
External links
| 40x40px | Wikimedia Commons has media related to [[commons:Category:{{#property:P373}}|Perlite]]. |
- The Perlite Institute
- Mineral Information Institute - perlite
- Perlite in Turkey World %68 Deposits in Turkeycs:Perlit
de:Perlit (Gestein) el:Περλίτης es:Perlita (geología) eo:Perlito fr:Perlite (roche) ko:펄라이트 is:Perlusteinn he:פרלייט hu:Perlit (kőzet) nl:Perliet (gesteente) ja:パーライト (岩石) pt:Perlite (geologia) ru:Перлит (порода) fi:Perliitti (vulkaaninen tuhka) sv:Perlit uk:Перліт zh:珍珠岩
