Tuffstone or tuff is a sedimentary rock formed by lithification of ashes and coarser ejecta from a volcanic outburst. It may be fine grained and well sorted but more usually incorporates coarser and poorly sorted fragments. The example here seen shows layers of fine ashes in which flow structures indicate that the ashes were wet or water saturated and possibly accumulated in a pool or lake. Actual tip to tip width is about 250 mm