Reticulite is basaltic pumice in which nearly all cell walls of gas bubbles have burst, leaving a honeycomb-like structure. Even though it is less dense than pumice, reticulite does not float in water because of the open network of bubbles. The delicate glass threads between the bubbles are so fragile that reticulite was first called "thread-lace scoria" by the great American mineralogist, James Dana. It has also been called limu.