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).
Autoclastic basaltic breccia is a rock composed of fragments of basalt and other rocks cemented together. The fragments formed in place by grinding of dike rock (tabular or sheetlike body of igneous rock).