Perlite

Perlite (from "perle" - pearls) - rock of a volcanic origin.
On a lava stream edge, in places of primary contact of magmatic fusions and a terrestrial surface, as a result of fast cooling (training) of a lava volcanic glass - obsidian is formed. Further underground waters get through obsidian, there is its hydration and formation of perlite.
Separateness small concentric - skorlupovataya (perlitovy structure) on which it breaks up to roundish kernels (pearls) reminding pearls with characteristic gloss is characteristic of perlite. Among other volcanic breeds perlite differs in availability of water of constitution (more than 1% ). Porosity can make 8 - 40% .
Perlite can have black, green, red - brown, brown, white coloring of various tones. Kinds of perlite: obsidianovy (with obsidian impurity), sferolitovy (with feldspar impurity), smolyanokamenny (uniform in structure), glassy and others.
On textural signs emit massive, striate, brekchiyevidny and pemzovidny perlites.