Thanks for the Sansa Clip suggestion. It looks like I'll definitely have to buy a compatible device to listen to audible books because audible will not play on just any MP3 player. They're as protectionist and anti-competitive as Australian publishers.
No rock is completely impermeable, but some porous rocks like shale and pumice are mostly impermeable, because the pores are not interconnected, thus not allowing fluids or gases to pass through them. This is why shale makes a good cap-rock, and pumice floats instead of sinking.
Pumice is a volcanic ash which is formed when lava is permeated with gas bubbles during the solidification process. Because lava has similar properties and chemical make-up as glass, pumice is very abrasive but unlike glass, it is very soft. Pumice is the softest abrasive media in use today. All Natural.ountry of Origin: United States. Pumice powder is made from pumice, a kind of igneous rock that is formed when a volcano erupts. Pumice is abrasive, which is where much of pumice powder's usefulness comes from. Cement. Pumice powder is used as an additive in cement.