Perlite is not a trade name but a generic term for naturally occurring siliceous volcanic rock. The distinguishing feature which sets Perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands four to twenty times of its original volume.

Perlite is amorphous volcanic glass that has 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.

Perlite is an industrial mineral and a commercial product useful for its light weight after processing. Perlite is a non-renewable resource. The world reserves of Perlite are estimated at 700 million tones.

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The chemical composition of Perlite:

SiO2 : 70–75%

Al2O3: 12–15%

Na2O: 3–4%

K2O: 3–5%

Fe2O3: 0.5-2%

MgO: 0.2–0.7%

CaO: 0.5–1.5%

LOI: 3–5%

Perlite is used in industries, agriculture, horticultural aggregate, vermiculite, refractory material, ladle topping, building construction products, fillers, filter aid and used in hot tops and risers. Because of 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 and ceiling tiles.

• 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.

• Perlite are also used in foundries, cryogenic, insulation, as a lightweight aggregate in mortar (fire stop) and in ceramics as a clay additive.