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.
When magma cools either above or underground, igneous rock is formed. What is the difference between intrusive and extrusive igneous rocks? Since Intrusive igneous rocks were formed underground, they had more time to release air and the size of the crystals is bigger. Extrusive rocks cool quickly so they don't have much time to compress together with all the crystals.