The developing among outdated volcanic rocks, the cavities are usually stuffed with deposits of secondary minerals launched by percolating water. The glass by itself types threads, fibres, and slim partitions among the vesicles. Rhyolite and trachyte pumices are white, andesite pumices generally yellow or brown, and pumiceous basalts (such as https://exactlybookmarks.com/story19374238/fascination-about-pumice-stone