Andesite, a fine-grained rock that is widely distributed in the earth's crust. Andesite reaches the surface as lava from volcanoes. As it cools it forms gray to grayish-black sheets, often in thick accumulations. Andesite consists chiefly of feldspar minerals mixed with smaller amounts of iron and magnesium. It was named for the Andes of South America, where it is widely found. Andesite is used for building stone and monuments.
Every day, astronomers unravel a little more of the universe's inner workings, but the jury is still out on 95 percent of its contents.
He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life. Here are 10 cool facts.