Explain Pumice
Pumice Technical Terms
Pumice: Rock fragments > 2 mm in diameter (i.e., retained upon a 2 mm sieve), or coherent rock layers (pumice flow), made of light-colored, vesicular, glassy rock commonly having the composition of rhyolite. The material commonly has a specific gravity of < 1.0 and is thereby sufficiently buoyant to float on water. SW; pumice-like fragments < 2 mm in size are called pumiceous ash. ST; Compare - scoria, tephra; (b) [geology] same as (a) but does not include any size restrictions. SW.