Classification of Sedimentary Rocks
Ash: unconsolidated fragments under. 4 mm. Tuff: consolidated ash. Volcanic Breccia: angular fragments over 4 mm. Agglomerate: large proportion (>25%) of bombs. These rocks are classified on the proportions of vitric, crystal (mineral), or lithic material they contain, for example, "vitric lithic ash," or "crystal vitric tuff."