Perlite

Perlite is an amorphous volcanic glass that has a relatively high water content. It occurs naturally and has the unusual property of greatly expanding when heated sufficently.

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When it reaches temperatures of 850–900 ?C, perlite softens (since it is a glass) and water trapped in the structure escapes and this causes the expansion of the material to 7–15 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles.

Amorphous: REDIRECT Amorphous solid...

Volcanic: REDIRECT Volcano...

Glass: :For eyeglasses, see glasses. For the drinking vessel, see glass (drinkware)....