Main Page | See live article | Alphabetical index Perlite is an amorphous glass mineral of volcanic origin. Typical analysis: 70-75% SiO2, 12-15% Al2O3, Na2O 3-4%, K2O 3-5%, Fe2O3 0,5-2%, MgO 0,2-0,7%, CaO 0,5-1,5% Loss On Ignition 3-5% Properties: When it reaches temperatures of 850-900C, perlite softens (since it is a glass) and water trapped in the structure escapes and this causes the expansion of the material at 7-15 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles. Unexpanded ("raw") perlite bulk density: around 1100 kg/m3 (1,1 gr/cm3) Typical expanded perlite bulk density: 30-150 kg/m3 Due to the low density of expanded perlite it has many uses: Lightweight plasters and mortars, insulation, ceiling tiles. In horticulture it makes composts more open to air, while still having good water-retention properties; it makes a good medium for hydroponics. See also: List of minerals Vermiculite This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.