7.2.2.1 Perlite. Production, Origin, and General Information—Perlite is a glassy volcanic rock with a rhyolitic composition and 2%–5% of combined water (Alkan and Dŏgan, 1998; Dŏgan and Alkan, 2004; Kaufhold et al., 2014 ). The major known global perlite resources (about 70%) are located along the Aegean coast in Turkey.