Perlite Introduction: Perlite Perlite is a vitreous rock formed by rapid cooling of acidic lava from volcanic eruptions. It is named after its pearly crack structure. Perlite minerals include perlite, obsidian and rosinite. The difference between the three is that perlite has arc-shaped cracks formed by condensation, called perlite structure, with a moisture content of 2 to 6%; rosinite has a unique rosin luster, with a moisture content of 6 to 10%; obsidian has glass Glossy and shell-shaped fractures, the moisture content is generally less than 2%.