The developing between previous volcanic rocks, the cavities are frequently full of deposits of secondary minerals introduced by percolating water. The glass by itself types threads, fibres, and slim partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices typically yellow or brown, and pumiceous basalts (such as https://olivebookmarks.com/story19507724/5-simple-techniques-for-pumice-stone