. . . . . . . . . . . . . . . . . "Tuff"@en . "Tuff - A type of pyroclastic-rock. In the Rock Classification Scheme, it is a pyroclastic-rock in which the average size of more than 75% of the pyroclastic fragments is less than 64 mm. Lapillistone, lapilli-tuff, and tuff are separated according to the relative proportion of lapilli-grade (2 - 64 mm) and ash-grade (<2 mm) fragments: if less than 25% of the fragments are lapilli the rock is tuff. It is the consolidated equivalent of ash. British Geological Survey Research Report RR/99/06, section 4.2 and fig. 4."@en . . . . . . . . . "stable"@en . "TUF"@en . . . . . "Tuff"@en . . . . . . .