tuff breccia - hand specimen of a spectacular pink tuff breccia

This particular volcanic igneous rock is composed of volcanic ash and many fragments (clasts) of other igneous rocks that were ejected from a volcanic vent. Because the ash was very hot when it fell to earth, the ash and rock fragments were welded together.  A breccia (from the Italian breccia for rubble) is normally composed of angular broken rock fragments that have been cemented together, such as where faulting has shattered rocks. In this case, there are so many broken fragments in this tuff that it is called a tuff breccia. The angular fragments in a breccia show that the fragments were cemented where they were formed. If they had been transported by running water, the edges would have become rounded. Tuffs are light colored, usually shades of buff or gray, and since they are silica rich, they are not dense. This pink tuff is spectacular, in part because of the varied clasts. A student should know that clasts, from the Greek klastos for broken in pieces, are characteristic of tuf