This rock is displayed in
Treasures” collection on the roofed patio of the visitor
center in the Robert Sibley Volcanic Regional
Preserve. The above caption is the same that is given on-site
(June 11, 2012).
Rhyolite is a light-colored volcanic rock composed of alkali feldspar, silica and minor amounts of mafic minerals (magnesium- and iron-rich minerals).
Rhyolite tuff is consolidated volcanic ash, containing rhyolite constituents and pumiceous, glassy fragments (glass shards).