The fragmented material is composed of pumice, glass, droplets of lava, and broken crystals. Some sorting and stratification are generally present. Material finer than 4 mm is known as Tuff . Material larger than 4 mm is referred to as volcanic breccia or agglomerate .
Glassy texture is similar to that of ordinary glass.
No crystals are present therefore no minerals are present even when the specimen is viewed under magnification. Vesicular Texture specimens are filled with air bubbles.