Tuff is similar to volcanic breccia, except that the fragments are smaller, and the matrix consists of fine volcanic material. You can find this in road cuts from Inarajan to Umatac, and as large chunks in Madog River in Umatac. Colors are most commonly white, pale tan or light green. It may stick to the tongue. You can find it around Leo Palace.
Pumice is foamy volcanic glass.
It has such a low density that it floats in water. The pumice found around here is generally white to gray in color. Pumice did not form on Guam, but floats in from other volcanic islands. It can be found on the beach, especially after typhoons. Concrete is a man-made rock resembling carbonate breccia or carbonate conglomerate.