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.
âº If a substance is permeable, it allows liquids or gases to go through it: Certain types of sandstone are permeable to water. The solvent passes through the permeable membrane to the solution. Soft and gas-permeable contact lenses are kinder to the eyes than hard lenses. Opposite. impermeable.