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.
Adj. 1. permeable-allowing fluids or gases to pass or diffuse through; permeable membranes; rock that is permeable by water. leaky-permitting the unwanted passage of fluids or gases; a leaky roof; a leaky defense system.. permeable-allowing fluids or gases to pass or diffuse through; permeable membranes; rock that is permeable by water. leaky-permitting the unwanted passage of fluids or gases; a leaky roof; a leaky defense system.