Industrial Minerals with emphasis on Western North America 263 MARILLA PERLITE- VOLCANIC GLASS OCCURRENCE, BRITISH

Perlite is a natural hydrated volcanic glass that displays concentric 'onion-skin-like ' fractures in hand sample or in thin section. It can occur as silicic lava domes, lava flows, welded ash-flow tuffs, glassy plugs, laccoliths and dikes. There are two main processes that cause hydration of perlite. Primary hydration occurs during formation of the rock before it has cooled; secondary hydration occurs after the rock has cooled and is the more important of the two processes. Perlite has a number of industrial and agricultural applications. There are at least 23 known occurrences in British Columbia, which are listed in MINFILE (a British Columbia computer-based mineral inventory system). There are currently no producing perlite mines i