The Anahim Peak perlite showing occurs in an area underlain by Tertiary volcanic rocks of the Ootsa Lake Group and Miocene basalt. The Ootsa Lake Group consists mainly of rhyolite and dacite with minor amounts of basalt and andesite. Epiclastic sedimentary rocks also occur within the group.
Although little information is available on this perlite occurrence, it is assumed that the perlite has formed from obsidian of the Ootsa Lake Group.