Can't download audible books to MP3 player - not happy, Jan. So I sprang the 50 bucks to buy a generic Dick Smith MP3 player because I thought - oh joy - I'd be able to carry my entire audible library around with me on a device that's as small as a matchbox. So I download some audible books. They're there on the device.
A common example of an extrusive igneous rock is basalt. Some extrusive rocks, such as obsidian and pumice, cool so rapidly that they completely lack crystal structure and are considered a volcanic glass. Pumice is just like obsidian except it is tiny shards of glass.
Another kind of intrusive rock is pumice which forms from granitic lava. This kind of lava is lighter colored, less dense and composed of silicon and oxygen. Pumice cools off very quickly and also is associated with gaseous eruptions. Therefore, pumice is very lightweight, and has very small crystals. Some pumice will float in water.