The developing amid aged volcanic rocks, the cavities are generally full of deposits of secondary minerals released by percolating h2o. The glass itself sorts threads, fibres, and slender partitions involving the vesicles. Rhyolite and trachyte pumices are white, andesite pumices usually yellow or brown, and pumiceous basalts (for example take https://admiralbookmarks.com/story19451075/the-pumice-stone-suppliers-diaries