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.
Best Answer: Permeability is a function of the amount of porespace in the rock and how interconnected the pore space is: granite and other intrusive igneous rocks have very interlocking grain structure and little pore space so low permeability.n metamorphic rocks the alignment of the platy minerals serves to further destroy permeability. Of the sedimentary rocks, shale or slate is least permeable (and thus forms good seals to oil and gas reservoirs), and sandstones and limestones most permeable.